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Noise & Vibration Worldwide     Full-text available via subscription   (Followers: 5)
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Nondestructive Testing And Evaluation     Hybrid Journal   (Followers: 8)
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Open Physics     Open Access   (Followers: 2)
Optical Communications and Networking, IEEE/OSA Journal of     Hybrid Journal   (Followers: 5)
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Pattern Recognition in Physics     Open Access   (Followers: 2)
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Phase Transitions and Critical Phenomena     Full-text available via subscription   (Followers: 1)
Philosophical Magazine     Hybrid Journal   (Followers: 2)
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences     Full-text available via subscription   (Followers: 6)
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Physica B: Condensed Matter     Hybrid Journal   (Followers: 5)
physica status solidi (a)     Hybrid Journal   (Followers: 1)
physica status solidi (b)     Hybrid Journal   (Followers: 1)
physica status solidi (c)     Hybrid Journal   (Followers: 1)
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Physics - spotlighting exceptional research     Full-text available via subscription   (Followers: 1)
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B     Full-text available via subscription   (Followers: 2)
Physics and Chemistry of Liquids: An International Journal     Hybrid Journal   (Followers: 2)
Physics and Chemistry of the Earth, Parts A/B/C     Hybrid Journal   (Followers: 3)
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Physics of Fluids     Hybrid Journal   (Followers: 26)
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Physics of the Dark Universe     Open Access   (Followers: 1)
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Physik in unserer Zeit     Hybrid Journal   (Followers: 1)
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Plasma Physics and Controlled Fusion     Hybrid Journal   (Followers: 3)
Plasma Physics Reports     Hybrid Journal   (Followers: 2)
Pramana     Open Access   (Followers: 9)
Preview     Hybrid Journal  
Proceedings of the National Academy of Sciences     Full-text available via subscription   (Followers: 461)
Proceedings of the National Academy of Sciences, India Section A     Hybrid Journal   (Followers: 3)
Progress in Materials Science     Hybrid Journal   (Followers: 21)
Progress in Planning     Hybrid Journal   (Followers: 1)
Progress of Theoretical and Experimental Physics     Open Access  
Quantum Electronics     Full-text available via subscription   (Followers: 3)
Quantum Measurements and Quantum Metrology     Open Access  
Quantum Studies : Mathematics and Foundations     Hybrid Journal   (Followers: 1)
Quarterly Journal of Mechanics and Applied Mathematics     Hybrid Journal   (Followers: 3)
Radiation Effects and Defects in Solids     Hybrid Journal   (Followers: 1)
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Research in Drama Education     Hybrid Journal   (Followers: 12)
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Reviews of Accelerator Science and Technology     Hybrid Journal  
Reviews of Geophysics     Full-text available via subscription   (Followers: 20)
Reviews of Modern Physics     Full-text available via subscription   (Followers: 17)
Revista Boliviana de Física     Open Access  
Revista Colombiana de Física     Open Access  
Revista Mexicana de Astronomía y Astrofísica     Open Access  
Revista Mexicana de Física     Open Access  
Revista mexicana de física E     Open Access  
Rheologica Acta     Hybrid Journal   (Followers: 3)
Russian Journal of Mathematical Physics     Hybrid Journal  
Russian Journal of Nondestructive Testing     Hybrid Journal   (Followers: 1)

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Journal Cover   Physics and Chemistry of the Earth, Parts A/B/C
  [SJR: 0.624]   [H-I: 42]   [3 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1474-7065
   Published by Elsevier Homepage  [2812 journals]
  • Temperature and heat wave trends in northwest mexico
    • Abstract: Publication date: Available online 26 July 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Polioptro F. Martínez-Austria, Erick R. Bandala, Carlos Patiño-Gómez
      Increase in temperature extremes is one of the main expected impacts of climate change, as well as one of the first signs of its occurrence. Nevertheless, results emerging from General Circulation Models, while sufficient for large scales, are not enough for forecasting local trends and, hence, the IPCC has called for local studies based on on-site data. Indeed, it is expected that climate extremes will be detected much earlier than changes in climate averages. Heat waves are among the most important and least studied climate extremes, however its occurrence has been only barely studied and even its very definition remains controversial. This paper discusses the observed changes in temperature trends and heat waves in Northwestern Mexico, one of the most vulnerable regions of the country. The climate records in two locations of the region are analyzed, including one of the cities with extreme climate in Mexico, Mexicali City in the state of Baja California and the Yaqui River basin at Sonora State using three different methodologies. Results showed clear trends on temperature increase and occurrence of heat waves in both of the study zones using the three methodologies proposed. As result, some policy making suggestion are included in order to increase the adaptability of the studied regions to climate change, particularly related with heat wave occurrence.

      PubDate: 2015-07-28T20:54:02Z
  • Regionalisation of precipitation for the iberian peninsula and climate
    • Abstract: Publication date: Available online 26 July 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): A.C. Parracho, P. Melo-Gonçalves, A. Rocha
      Temporal variability of precipitation over the Iberian Peninsula (IP) has high spatial gradients. Therefore, statistics of the temporal behaviour of precipitation and derived quantities over the IP must be estimated taking into account these spatial gradients. Some statistics can be displayed over a map. However there are statistics, such as Probability Density Functions at each location of the IP, that are impossible to display in a map. Because of this, it is mandatory to reduce the number of degrees of freedom which, in this case, consists of a reduction of the time series representative of the IP domain. In this work, we present a spatial partition of the IP region into areas of similar precipitation. For that, an observed dataset of daily-total precipitation for the years between 1951 and 2003 was used. The land-only high resolution data was obtained on a regular grid with 0.2° resolution in the IP domain. This data was subjected to a K-means Cluster Analysis in order to divide the IP into K regions. The clustering was performed using the squared Euclidean distance. Four clusters of IP grid points, defining 4 IP regions, were identified. The grid points in each region share the same time-varying behaviour which is different from region to region. The annual precipitation discriminates the following regions: (i) northwest Iberia, (ii) north Iberia, (iii) a large region ranging from the centre to the western and southwestern shores of the Iberia, and (iv) another large region extending from the centre to the Mediterranean shores of the IP. The regions obtained for the four seasons of the year are similar. These results are consistent with the thermodynamic characteristics described in the available literature. These Iberian regions were used to assess climate change of seasonal precipitation from the multi-model ensemble of the fifteen simulations provided by the European project ENSEMBLES. Probability Density Functions of seasonal-total precipitation averaged in each region were estimated for a reference climate (1961-1960), a near-future climate (2021-2050), and a distant-future climate (2069-2098). Climate change projections are based on comparisons of these functions between each future climate and the reference climate. Finally we emphasize that: (i) the methodology used here, based on Cluster Analysis, can be used to regionalise other areas of the world, and (ii) the identified regions of the IP can be used to represent the Iberian precipitation by four time series that can be subjected to further analysis, and whose results can be presented in a concise manner.

      PubDate: 2015-07-28T20:54:02Z
  • Estimation of Snow Density Using Full-Polarimetric Synthetic Aperture
           Radar (SAR) Data
    • Abstract: Publication date: Available online 16 July 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): M. Surendar, A. Bhattacharya, G. Singh, G. Venkataraman
      In this paper, a new snow density estimation methodology is proposed for full-polarimetric Synthetic Aperture Radar (SAR) data. The generalized four component polarimetric decomposition with unitary transformation (G4U) based generalized volume parameter is utilized to invert snowpack dielectric constant using the Fresnel transmission coefficients. The snow density is then estimated using an empirical relationship. Six Radarsat-2 fine resolution full-polarimetric C-band datasets were acquired over Himachal Pradesh, India. The near-real time in-situ measurements were collected with the satellite pass to validate the proposed method. The mean absolute error (MAE) of the proposed method is 0.027 gcm-3 and the root mean square error (RMSE) is 0.032 gcm-3. The snow density variation within a season were also analyzed using multi-temporal Radarsat-2 data.

      PubDate: 2015-07-16T21:35:44Z
  • Slope angle and aspect as influencing factors on the accuracy of the SRTM
           and the ASTER GDEM databases
    • Abstract: Publication date: Available online 2 July 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Gergely Szabó , Sudhir Kumar Singh , Szilárd Szabó
      Presently, the application of digital elevation or surface models have increasing relevance in all areas of scientific research and in practical engineering applications. The ASTER GDEM and SRTM databases are the most widely used digital surface models, due to their free accessibility and global coverage. The SRTM model was produced using a radar-based technique and the ASTER GDEM was developed using optical stereo image-pairs. Therefore, as all models contain errors (i.e. differences stemming from real surface or vertical biases), errors in these models will also differ. Our aim was to examine these vertical biases and to calculate the rate of error variance. A TIN (Triangulated Irregular Network) model was used as a reference surface, derived from the contour lines of a large scale topographic map. Errors were evaluated with statistical and geoinformation techniques. We discovered significant differences between the surfaces. The mean difference between topographic elevations minus the SRTM-V2 is +2.6±4 meters, while the mean difference between topographic elevations minus the SRTM-V3 is +2.7±2.5 meters. With the GDEM, the mean difference was 2.7±9.1 meters. Furthermore, we found that in the case of SRTM, the differences were significant considering the aspects and the steepness of the slopes: southern and eastern directions and larger slope angles showed greater differences compared to the reference data. ‘The GDEM V2 DEM had a larger error variance, but the error did not vary significantly with slope angle.

      PubDate: 2015-07-05T15:35:20Z
  • Evaluation of SMOS soil moisture retrievals over the central United States
           for hydro-meteorological application
    • Abstract: Publication date: Available online 2 July 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Lu Zhuo , Qiang Dai , Dawei Han
      Soil moisture has been widely recognized as a key variable in hydro-meteorological processes and plays an important role in hydrological modelling. Remote sensing techniques have improved the availability of soil moisture data, however, most previous studies have only focused on the evaluation of retrieved data against point-based observations using only one overpass (i.e., the ascending orbit). Recently, the global Level-3 soil moisture dataset generated from Soil Moisture and Ocean Salinity (SMOS) observations was released by the Barcelona Expert Center. To address the aforementioned issues, this study is particularly focused on a basin scale evaluation in which the soil moisture deficit is derived from a three-layer Xinanjiang model used as a hydrological benchmark for all comparisons. In addition, both ascending and descending overpasses were analyzed for a more comprehensive comparison. It was interesting to find that the SMOS soil moisture accuracy did not improve with time as we would have expected. Furthermore, none of the overpasses provided reliable soil moisture estimates during the frozen season, especially for the ascending orbit. When frozen periods were removed, both overpasses showed significant improvements (i.e., the correlations increased from r =−0.53 to r =−0.65 and from r =−0.62 to r =−0.70 for the ascending and descending overpasses, respectively). In addition, it was noted that the SMOS retrievals from the descending overpass consistently were approximately 11.7% wetter than the ascending retrievals by volume. The overall assessment demonstrated that the descending orbit outperformed the ascending orbit, which was unexpected and enriched our knowledge in this area. Finally, the potential reasons were discussed.

      PubDate: 2015-07-05T15:35:20Z
  • Impact of land-use induced changes on agricultural productivity in the
           Huang-Huai-Hai River Basin
    • Abstract: Publication date: 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volumes 79–82
      Author(s): Gui Jin , Zhaohua Li , Zhan Wang , Xi Chu , Zhihui Li
      The water resource allocation is greatly influenced by the land use, agricultural productivity and farmers’ income. Therefore analyzing the impacts of land use changes on agricultural productivity and subsequent effects on farmer’s income is an important basis of the further study on the management mechanism and optimal water resource allocation. Taking the Huang-Huai-Hai River Basin as the study area, this study examined the impacts of conversion from cultivated land to built-up land from 2000–2005 and 2005–2008. Then the agricultural productivity was estimated with the Estimation System for Agricultural Productivity model, and the changes in agricultural productivity caused by land conversion were analyzed. Thereafter, Simultaneous Equations Model was used to analyze the impacts of the conversion from cultivated land to built-up land on the agricultural productivity and subsequent effects on farmer’s income. The results showed that: (1) The agricultural productivity was stable during the whole period, reaching about 2.84ton/ha, 3.09ton/ha and 2.80ton/ha on average in 2000, 2005 and 2008, respectively, but the conversion from cultivated land to built-up land had important influence on the spatial pattern of agricultural productivity. (2) The land productivity, total power of agricultural machinery and the conversion from cultivated land to built-up land had an overall positive effect on the agricultural productivity. (3) The agricultural productivity and gross domestic product had positive influence on the farmers’ income, while the cultivated land area per capita and percentage of farming employee had negative influence, indicating that the farmer’s income was mainly contributed by non-agricultural income. These results in this study showed that optimal land use management can play an important role in promoting virtuous ecosystem cycle and sustainable socioeconomic development, which can also lay an important foundation for further research on the optimal allocation of water resources in the Huang-Huai-Hai River Basin.

      PubDate: 2015-06-26T14:37:28Z
  • Long-term SMOS soil moisture products: A comprehensive evaluation across
           scales and methods in the Duero Basin (Spain)
    • Abstract: Publication date: Available online 4 June 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Ángel González-Zamora , Nilda Sánchez , José Martínez-Fernández , Ángela Gumuzzio , María Piles , Estrella Olmedo
      The European Space Agency’s Soil Moisture and Ocean Salinity (SMOS) Level 2 soil moisture and the new L3 product from the Barcelona Expert Center (BEC) were validated from January 2010 to June 2014 using two in situ networks in Spain. The first network is the Soil Moisture Measurement Stations Network of the University of Salamanca (REMEDHUS), which has been extensively used for validating remotely sensed observations of soil moisture. REMEDHUS can be considered a small-scale network that covers a 1300km2 region. The second network is a large-scale network that covers the main part of the Duero Basin (65,000km2). At an existing meteorological network in the Castilla y Leon region (Inforiego), soil moisture probes were installed in 2012 to provide data until 2014. Comparisons of the temporal series using different strategies (total average, land use, and soil type) as well as using the collocated data at each location were performed. Additionally, spatial correlations on each date were computed for specific days. Finally, an improved version of the Triple Collocation (TC) method, i.e., the Extended Triple Collocation (ETC), was used to compare satellite and in situ soil moisture estimates with outputs of the Soil Water Balance Model Green-Ampt (SWBM-GA). The results of this work showed that SMOS estimates were consistent with in situ measurements in the time series comparisons, with Pearson correlation coefficients (R) and an Agreement Index (AI) higher than 0.8 for the total average and the land-use averages and higher than 0.85 for the soil-texture averages. The results obtained at the Inforiego network showed slightly better results than REMEDHUS, which may be related to the larger scale of the former network. Moreover, the best results were obtained when all networks were jointly considered. In contrast, the spatial matching produced worse results for all the cases studied. These results showed that the recent reprocessing of the L2 products (v5.51) improved the accuracy of soil moisture retrievals such that they are now suitable for developing new L3 products, such as the presented in this work. Additionally, the validation based on comparisons between dense/sparse networks and satellite retrievals at a coarse resolution showed that temporal patterns in the soil moisture are better reproduced than spatial patterns.

      PubDate: 2015-06-26T14:37:28Z
  • The contribution of tropical cyclones to rainfall in Mexico
    • Abstract: Publication date: Available online 4 June 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): J. Agustín Breña-Naranjo , Adrián Pedrozo-Acuña , Oscar Pozos-Estrada , Salma A. Jiménez-López , Marco R. López-López
      Investigating the contribution of tropical cyclones to the terrestrial water cycle can help quantify the benefits and hazards caused by the rainfall generated from this type of hydro-meteorological event. Rainfall induced by tropical cyclones can enhance both flood risk and groundwater recharge, and it is therefore important to characterise its minimum, mean and maximum contributions to a region or country’s water balance. This work evaluates the rainfall contribution of tropical depressions, storms and hurricanes across Mexico from 1998 to 2013 using the satellite-derived precipitation dataset TMPA 3B42. Additionally, the sensitivity of rainfall to other datasets was assessed: the national rain gauge observation network, real-time satellite rainfall and a merged product that combines rain gauges with non-calibrated space-borne rainfall measurements. The lower Baja California peninsula had the highest contribution from cyclonic rainfall in relative terms (∼40% of its total annual rainfall), whereas the contributions in the rest of the country showed a low-to-medium dependence on tropical cyclones, with mean values ranging from 0% to 20%. In quantitative terms, southern regions of Mexico can receive more than 2400mm of cyclonic rainfall during years with significant TC activity. Moreover, (a) the number of tropical cyclones impacting Mexico has been significantly increasing since 1998, but cyclonic contributions in relative and quantitative terms have not been increasing, and (b) wind speed and rainfall intensity during cyclones are not highly correlated. Future work should evaluate the impacts of such contributions on surface and groundwater hydrological processes and connect the knowledge gaps between the magnitude of tropical cyclones, flood hazards, and economic losses.

      PubDate: 2015-06-26T14:37:28Z
  • Integrating TRMM and MODIS satellite with socio-economic vulnerability for
           monitoring drought risk over a tropical region of India
    • Abstract: Publication date: Available online 19 February 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Aradhana Yaduvanshi , Prashant K. Srivastava , A.C. Pandey
      Drought is a recurring feature of the climate, responsible for social and economic losses in India. In the present work, attempts were made to estimate the drought hazard and risk using spatial and temporal datasets of Tropical Rainfall Measuring Mission (TRMM) and Moderate Resolution Imaging Spectroradiometer (MODIS) in integration with socio-economic vulnerability. The TRMM rainfall was taken into account for trend analysis and Standardized Precipitation Index (SPI) estimation, with aim to investigate the changes in rainfall and deducing its pattern over the area. The SPI and average rainfall data derived from TRMM were interpolated to obtain the spatial and temporal pattern over the entire South Bihar of India, while the MODIS datasets were used to derive the Normalized Difference Vegetation Index (NDVI) deviation in the area. The Geographical Information System (GIS) is taken into account to integrate the drought vulnerability and hazard, in order to estimate the drought risk over entire South Bihar. The results indicated that approximately 36.90% area is facing high to very high drought risk over north-eastern and western part of South Bihar and need conservation measurements to combat this disaster.

      PubDate: 2015-06-26T14:37:28Z
  • Seismo-meteo-electromagnetic phenomena observed during a 5-year interval
           around the 2011 Tohoku earthquake
    • Abstract: Publication date: Available online 19 February 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Alexander Schekotov , Masashi Hayakawa
      The purpose of the paper is to try to find ULF electromagnetic precursors to the 2011 Tohoku earthquake (EQ), on the basis of extensive investigation of radiations in vertical component of the magnetic field or with a large ratio of the vertical to full horizontal component. Nighttime records have been analyzed of three Japanese fluxgate magnetometers located in a distance from 300 to 1300km from the epicenter of the main shock, and the frequency range from 10 to 150mHz was used for the analysis. We have applied wavelet analyses to improve the detection of pulsed signals. All obtained scalograms have been averaged over the nighttime interval from 01h to 05h JST and flattened by means of multiplication by square of frequency. The sequence of spectra thus obtained has been compared with the evolution of seismicity, which has resulted in that the radiation in the vertical component has been detected. It exhibits seasonal variations with winter maxima, but it increases further by approaching the moment of the EQ and decreases after that. This radiation seems to be correlated with atmospheric parameters – air humidity, temperature, vapor pressure and rainfall. So, we consider that this radiation cannot be caused by subsurface sources, but its possible sources can be atmospheric discharges. The evolution of this phenomenon can be explained by a seasonal variation of atmospheric parameters and also its variations under the influence of injection of gas from the focal zone of a forthcoming EQ.

      PubDate: 2015-06-26T14:37:28Z
  • On diurnal dependence and spatial scales of seismo-ionospheric effects in
           the E-layer
    • Abstract: Publication date: Available online 19 February 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): E.V. Liperovskaya , C.-V. Meister , D.H.H. Hoffmann , A.S. Silina
      In the present work, disturbances of the f b E s -frequency of the sporadic E-layer of the ionosphere are investigated in connection with earthquakes. The f b E s -frequency is proportional to the square root of the maximum ionisation density of the sporadic E-layer. In this work, it is shown that two days before a seismic shock with magnitude M > 5.5 , and during the shock, an increase of the f b E s -frequency is obtained around midnight at distances from the epicentre R < exp M + 100 km in the case that the focus of the shock was situated at depths smaller than 60km. Data obtained by the three ionospheric sounding stations “Kokubunji”, “Akita” and “Yamagawa” are analysed, which were recorded during a total time of 42years. The superimposed epoches method is applied for a few tens of earthquakes.

      PubDate: 2015-06-26T14:37:28Z
  • VLF/LF signal studies of the ionospheric response to strong seismic
           activity in the Far Eastern region combining the DEMETER and ground-based
    • Abstract: Publication date: Available online 21 February 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): A. Rozhnoi , M. Solovieva , M. Parrot , M. Hayakawa , P.-F. Biagi , K. Schwingenschuh , V. Fedun
      The paper presents the results of a joint analysis of ground-based and satellite observations of very low-frequency and low-frequency (VLF/LF) signals during periods of strong seismic activity in the region of Kuril Islands and Japan in 2004–2010. Ground and satellite data was processed using a method based on the difference between the real signal in nighttime and that of a model. The results of the analysis show a good correlation between ground-based and satellite data for several cases of strong (M ⩾6.8) earthquakes.

      PubDate: 2015-06-26T14:37:28Z
  • Time–frequency analysis of VLF for seismic-ionospheric precursor
           detection: Evaluation of Zhao-Atlas-Marks and Hilbert-Huang Transforms
    • Abstract: Publication date: Available online 21 February 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): C. Skeberis , Z.D. Zaharis , T.D. Xenos , S. Spatalas , D.N. Arabelos , M.E. Contadakis
      This work investigates the application of two post-processing methods of extracting spectra from VLF signals in order to detect disturbances that could be attributed to seismic-ionospheric precursory phenomena. Although precursory phenomena have been investigated in detail in past studies, a different application of time–frequency analysis methods may produce distinct patterns, which reveal disturbances in the VLF spectra received from stations that are in the propagation path over preparation zones, and also pinpoint disturbances that could be attributed to seismic-ionospheric precursors. To this purpose, three different methods of post processing are compared. These are the Wavelet Transform as a benchmark method in the form of the Continuous Wavelet Transform, a noise-assisted variant of the Hilbert-Huang Transform and the Zhao-Atlas-Marks Distribution. Comparative diagrams are presented and the advantages and weaknesses of each method are presented.

      PubDate: 2015-06-26T14:37:28Z
  • Inferring land surface parameters from the diurnal variability of
           microwave and infrared temperatures
    • Abstract: Publication date: Available online 27 February 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Hamidreza Norouzi , Marouane Temimi , Amir AghaKouchak , Marzieh Azarderakhsh , Reza Khanbilvardi , Gerarda Shields , Kibrewossen Tesfagiorgis
      This study investigates the properties of the diurnal cycle of microwave brightness temperatures (TB), namely the phase and the amplitude, and their variability in time and space over the globe to infer information on key land surface parameters like changes in soil texture spatial distribution, soil moisture conditions, and vegetation density. The phase corresponds to the lag between Land Surface Temperature (LST) and TB diurnal cycles. The amplitude is determined as the difference between the maximum and the minimum of TB diurnal cycle. The diurnal cycle of TB was constructed using observations from the Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) and the Special Sensor Microwave/Imager (SSM/I). The latter offer a series of sensors, namely, F13, F14, and F15 that were used in this study for a higher temporal coverage and more accurate diurnal cycle determination. LST estimates, which are available every 3h from the International Satellite Cloud Climatology Project (ISCCP) database were used to build the LST diurnal cycle. ISCCP LST data is an infrared-based temperature with almost no penetration and is the representative of top skin temperature. The analyses of the diurnal cycles showed that the diurnal amplitude of TB decreases as the vegetation density increases, especially in the case of low frequencies which penetrate deeper into the canopy which makes them more sensitive to changes in vegetation density. The interannual variations of TB diurnal amplitudes were also in agreement with the seasonality of the vegetation cover. Over desert and rain forest regions where surface conditions do not vary significantly throughout the year, the changes in diurnal amplitudes were the lowest. A relationship between phase and amplitude values was established. It was found that the amplitude of TB diurnal cycle decreases when the phase lag increases. The spatial distribution of the determined diurnal properties, namely, phase and amplitude of TB, showed an agreement with lithology maps in desert areas. Lower TB amplitudes were observed over regions with loose siliceous rocks. Phase lag values between 1.5 and 3h corresponded to 83% of the class “loose siliceous rocks” in the Sahara Desert, which corroborates the potential of using the diurnal properties of TB as an indicator of land surface parameters.

      PubDate: 2015-06-26T14:37:28Z
  • Evidence for tidal triggering on the earthquakes of the Hellenic Arc,
    • Abstract: Publication date: Available online 28 February 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): G. Vergos , D.N. Arabelos , M.E. Contadakis
      In this paper we investigate the tidal triggering evidence on the earthquakes of the seismic area of the Hellenic Arc using the Hist(ogram)Cum(mulation) method. We analyze the series of the earthquakes occurred in the area which is confined by the longitudes 22° and 28°E and latitudes 34° and 36°N in the time period from 1964 to 2012. In this time period 16,137 shallow and of intermediate depth earthquakes with ML up to 6.0 and 1,482 deep earthquakes with ML up to 6.2 occurred. The result of the this analysis indicate that the monthly variation of the frequencies of earthquake occurrence is in accordance with the period of the tidal lunar monthly variations, and the same happens with the corresponding daily variations of the frequencies of earthquake occurrence with the diurnal luni-solar (K1) and semidiurnal solar (S2) tidal variations. These results are in favor of a tidal triggering process on earthquakes when the stress in the focal area is near the critical level.

      PubDate: 2015-06-26T14:37:28Z
  • A qualitative study of seismic-ionospheric precursor phenomena monitored
           by a very close to the epicenter VLF and LF receiver
    • Abstract: Publication date: Available online 5 March 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): C. Skeberis , Z.D. Zaharis , T.D. Xenos , S. Spatalas , M.E. Contadakis
      This work investigates the occurrence of disturbances across a wide range of VLF and LF frequencies received prior to a seismic event (Mw=4), that took place on May 12th 2012, the epicenter of which was very close (14km) to the VLF/LF station. The signals analyzed were emitted from five VLF and five LF European transmitters. This seismic event produced precursory ionospheric disturbances, identified as spectral distortion, three days before its occurrence, providing a distinct pattern open to further investigation. Although the basis of the ionosphere interaction with seismic phenomena has been well documented in previous studies, the close proximity of the receiver to the seismic event provides a new perspective to this study. The monitored signals have undergone normalization and then they have been processed by means of the Hilbert-Huang Transform. Diagrams of the signals relevant to the phenomena are presented and the disturbances that are present in the raw data are accentuated through further processing.

      PubDate: 2015-06-26T14:37:28Z
  • Precursory signatures in the visibility graph analysis of seismicity: An
           application to the Kachchh (Western India) seismicity
    • Abstract: Publication date: Available online 14 March 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Luciano Telesca , Michele Lovallo , S.K. Aggarwal , P.K. Khan
      The Visibility Graph (VG) method maps time series into networks or graphs, converting dynamical properties of time series in topological properties of networks. The VG method was applied to the aftershock depleted catalogue of the Kachchh Gujarat (Western India) seismicity from 2003 to 2012, in order to identify possible precursory signatures in the pattern of the VG parameters. The k – M slope (the slope of the line fitting the relationship between the magnitude of the events and their connectivity degrees) seems to sharply increase significantly before the occurrence of the largest shocks (M ⩾4.5) of the sequence.

      PubDate: 2015-06-26T14:37:28Z
  • A temperature-dependent multi-relaxation spectroscopic dielectric model
           for thawed and frozen organic soil at 0.05–15GHz
    • Abstract: Publication date: Available online 14 March 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Valery Mironov , Igor Savin
      A dielectric model for thawed and frozen Arctic organic-rich soil (50% organic matter) has been developed. The model is based on soil dielectric measurements that were collected over ranges of gravimetric moisture from 0.03 to 0.55g/g, dry soil density from 0.72 to 0.87g/cm3, and temperature from 25 to −30°C (cooling run) in the frequency range of 0.05–15GHz. The refractive mixing dielectric model was applied with the Debye multi-relaxation equations to fit the measurements of the soil’s complex dielectric constant as a function of soil moisture and wave frequency. The spectroscopic parameters of the dielectric relaxations for the bound, transient bound, and unbound soil water components were derived and were complimented by the thermodynamic parameters to obtain a complete set of parameters for the proposed temperature-dependent multi-relaxation spectroscopic dielectric model for moist soils. To calculate the complex dielectric constant of the soil, the following input variables must be assigned: (1) density of dry soil, (2) gravimetric moisture, (3) wave frequency, and (4) temperature. The error of the dielectric model was evaluated and yielded RMSE ε ′ values of 0.348 and 0.188 for the soil dielectric constant and the loss factor, respectively. These values are on the order of the dielectric measurement error itself. The proposed dielectric model can be applied in active and passive microwave remote sensing techniques to develop algorithms for retrieving the soil moisture and the freeze/thaw state of organic-rich topsoil in the Arctic regions.

      PubDate: 2015-06-26T14:37:28Z
  • Anomalous CO2 content in the Gallicano thermo-mineral spring (Serchio
           Valley, Italy) before the 21 June 2013, Alpi Apuane earthquake (M=5.2)
    • Abstract: Publication date: Available online 14 March 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): L. Pierotti , F. Botti , V. D’Intinosante , G. Facca , F. Gherardi
      Since late 2002, a continuous automatic monitoring network is operating in Tuscany, Central Italy, to investigate the geochemical response of selected aquifers to local seismic activity. The monitoring is aimed at identifying possible earthquake geochemical precursors. The network is currently constituted by six stations, all equipped with sensors for the measurement of temperature, pH, redox potential, electrical conductivity, CO2 and CH4 dissolved concentration, that have been installed in the areas of highest seismic risk of the region. By combining geochemical data gathered from the automatic station of Gallicano (Garfagnana, Northern Tuscany), and obtained via chemical analyses of spring water samples collected during periodic field surveys in the area surrounding this station, the most significant aspects of the deep fluid circulation paths feeding the Gallicano thermo-mineral system have been investigated, and the geochemical baseline of the Gallicano spring defined. The CO2 continuous signal recorded by the Gallicano automatic station has been then processed over the period 2003–2013 in the search for anomalies possibly related to local seismic activity. A substantial anomaly in CO2 content has been observed at Gallicano in conjunction with the Alpi Apuane earthquake (M =5.2) of 21 June 2013.

      PubDate: 2015-06-26T14:37:28Z
  • Surface soil moisture retrievals from remote sensing: Current status,
           products &amp; future trends
    • Abstract: Publication date: Available online 14 March 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): George P. Petropoulos , Gareth Ireland , Brian Barrett
      Advances in Earth Observation (EO) technology, particularly over the last two decades, have shown that soil moisture content (SMC) can be measured to some degree or other by all regions of the electromagnetic spectrum, and a variety of techniques have been proposed to facilitate this purpose. In this review we provide a synthesis of the efforts made during the last 20years or so towards the estimation of surface SMC exploiting EO imagery, with a particular emphasis on retrievals from microwave sensors. Rather than replicating previous overview works, we provide a comprehensive and critical exploration of all the major approaches employed for retrieving SMC in a range of different global ecosystems. In this framework, we consider the newest techniques developed within optical and thermal infrared remote sensing, active and passive microwave domains, as well as assimilation or synergistic approaches. Future trends and prospects of EO for the accurate determination of SMC from space are subject to key challenges, some of which are identified and discussed within. It is evident from this review that there is potential for more accurate estimation of SMC exploiting EO technology, particularly so, by exploring the use of synergistic approaches between a variety of EO instruments. Given the importance of SMC in Earth’s land surface interactions and to a large range of applications, one can appreciate that its accurate estimation is critical in addressing key scientific and practical challenges in today’s world such as food security, sustainable planning and management of water resources. The launch of new, more sophisticated satellites strengthens the development of innovative research approaches and scientific inventions that will result in a range of pioneering and ground-breaking advancements in the retrievals of soil moisture from space.

      PubDate: 2015-06-26T14:37:28Z
  • Comprehensive hydrologic calibration of SWAT and water balance analysis in
           mountainous watersheds in northwest China
    • Abstract: Publication date: 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volumes 79–82
      Author(s): Zhixiang Lu , Songbing Zou , Honglang Xiao , Chunmiao Zheng , Zhenliang Yin , Weihua Wang
      Model calibration is important for streamflow simulations using distributed hydrological models, especially in highland and cold areas of northwest China with scarce data. Quantitative analysis of water balance based on the accurate simulation is also essential for reasonably planning and managing water resources in these river basins facing a severe water shortage. In this study, a comprehensive method was proposed to calibrate the Soil and Water Assessment Tool (SWAT) model in the Yingluoxia watershed, upstream area of the Heihe River basin; it was based on multi-temporal, multi-variable and multi-site integrated drainage characteristics. Meanwhile a fresh approach of the parameter transferability and model validation was used by applying the set of calibrated parameters in its tributary to other area of the watershed. The results indicated that the method was effective and feasible; the values of Nash–Sutcliffe Efficiency (NSE) and Coefficient of Determination (r 2) were greater than 0.81 and as high as 0.94 and the absolute values of the Percent Bias (PBIAS) were less than 2. Based the output of model the water balance in the Yingluoxia watershed was analyzed, that the mean annual precipitation, evapotranspiration, and discharge of the watershed from 1990 to 2000 were 491.8mm, 334mm, and 157.8mm, respectively. The comprehensive calibration method based on multi-temporal, multi-variable and multi-site integrated drainage characteristics can better portray the hydrological processes of watershed and improve the model simulation; and the output of the model then provide a reliable reference for assessing and managing water resource of the watershed.

      PubDate: 2015-06-26T14:37:28Z
  • Simulated water productivity in Gansu Province, China
    • Abstract: Publication date: 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volumes 79–82
      Author(s): Jinyan Zhan , Zhongxiao Sun , Zhan Wang , Jiancheng Chen , Zhaohua Li
      Economic value of water and economic analysis of water use management in Gansu Province of China have attracted widespread public attention. With the socioeconomic development, research on water resources has become more important than before. In this study, we define “water productivity” as the changes of economic production outputs of sectoral activities in every cubic meter of water input, which is also the technical coefficient of water resource use in each sector. According to Computable General Equilibrium (CGE) framework, based on the Input–Output Table 2007 and water resources bulletin of Gansu Province, we introduced the water into the ORANI-G (A Generic Single-Country Computable General Equilibrium model) model through the nested constant elasticity of substitution (CES) production function to analyze the changes of economic productions caused by water supply changes. We then examined water productivity in different sectors. Empirical results showed that current water productivity is underestimated. Agricultural water productivity is lower than that of the secondary and tertiary industries, even although agricultural water use is the largest part of water use in Gansu Province, and therefore improving agricultural water productivity can greatly mitigate the water shortage. Simulation results indicate that industrial transformation and development of water-saving industries will also mitigate water scarcity. Moreover, sensitivity analysis shows that the empirical results are robust under different scenarios. The results also show that higher constant elasticity of substitution rate (CES) between water and other production factors will contribute to sustainable development.

      PubDate: 2015-06-26T14:37:28Z
  • Impact analysis of government investment on water projects in the arid
           Gansu Province of China
    • Abstract: Publication date: 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volumes 79–82
      Author(s): Zhan Wang , Xiangzheng Deng , Xiubin Li , Qing Zhou , Haiming Yan
      In this paper, we introduced three-nested Constant Elasticity of Substitution (CES) production function into a static Computable General Equilibrium (CGE) Model. Through four levels of factor productivity, we constructed three nested production function of land use productivity in the conceptual modeling frameworks. The first level of factor productivity is generated by the basic value-added land. On the second level, factor productivity in each sector is generated by human activities that presents human intervention to the first level of factor productivity. On the third level of factor productivity, water allocation reshapes the non-linear structure of transaction among first and second levels. From the perspective of resource utilization, we examined the economic efficiency of water allocation. The scenario-based empirical analysis results show that the three-nested CES production function within CGE model is well-behaved to present the economy system of the case study area. Firstly, water scarcity harmed economic production. Government investment on water projects in Gansu thereby had impacts on economic outcomes. Secondly, huge governmental financing on water projects bring depreciation of present value of social welfare. Moreover, water use for environment adaptation pressures on water supply. The theoretical water price can be sharply increased due to the increasing costs of factor inputs. Thirdly, water use efficiency can be improved by water projects, typically can be benefited from the expansion of water-saving irrigation areas even in those expanding dry area in Gansu. Therefore, increasing governmental financing on water projects can depreciate present value of social welfare but benefit economic efficiency for future generation.
      Graphical abstract image

      PubDate: 2015-06-26T14:37:28Z
  • An input–output table based analysis on the virtual water by sectors
           with the five northwest provinces in China
    • Abstract: Publication date: 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volumes 79–82
      Author(s): Chenchen Shi , Jinyan Zhan
      Virtual water refers to the volumes of water required to produce a commodity or service. It reflects human’s actual consumption of water resources and therefore has certain significance in water resources management. Over the years, the concept of virtual water has caught the attentions of water manager and decision maker. In order to utilize this concept, the accounting and estimation of virtual water is the foundation that lies in this issue. Till now, the accounting methods mainly include the method provided by Food and Agriculture Organization of the United Nations (FAO), water footprint and input–output analysis method. In this paper, we chose Northwest China, which is a typical arid region that is facing with rapid economic development, as the study area and built an Input–Output (IO) analysis method to estimate virtual water among different industry sectors in the northwest China. The accounting and estimation results could be used to give suggestions to increase water use efficiency and promote virtual water trade in the study area. Comparison of the proposed method with other prevailing method was also analyzed. The introduced method could be utilized for accounting and estimation of virtual water by sectors, with its superiority in characterizing industrial water consumption and the accounting results could lend certain credence to the water resource management and industrial transformation for the future economic development of northwest China.

      PubDate: 2015-06-26T14:37:28Z
  • Multilevel modeling of NPP change and impacts of water resources in the
           Lower Heihe River Basin
    • Abstract: Publication date: 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volumes 79–82
      Author(s): Haiming Yan , Jinyan Zhan , Qun’ou Jiang , Yongwei Yuan , Zhihui Li
      Net primary productivity (NPP) lays the foundation for provision of various ecosystem services, and understanding the impacts of potential influencing factors on NPP is of great significance to formulating appropriate management measures to guarantee the sustainable provision of essential ecosystem services. This study analyzed the impacts of potential influencing factors on NPP in the lower Heihe River Basin, a typical arid and semi-arid region in China. First, NPP was estimated with the C-FIX model, and then the multilevel model was used to analyze the impacts of potential influencing factors on NPP during 2000–2008. Finally decomposition analysis was used to further analyze the contribution of influencing factors to NPP change during 2000–2008. The average NPP increased by approximately 9.07% during 2000–2008, and results of the multilevel model indicate that both the socioeconomic variables and demographic variables are useful in explaining NPP change. In particular, coefficients of rainfall and evapotranspiration which represent the water availability reached 0.0456 and 0.2956, respectively. Results of decomposition analysis suggested that the water availability played an important role in increasing NPP, with a contribution rate of 44.17%, and it is necessary to carry out some policies that can promote the water use efficiency to increase NPP under the background of climate change and intensified human activities. There are some uncertainties in the results of this study, but these results still can provide valuable reference information for the water resource management to increase the ecosystem service supply in the lower Heihe River Basin.

      PubDate: 2015-06-26T14:37:28Z
  • Assessing the regional spatio-temporal pattern of water stress: A case
           study in Zhangye City of China
    • Abstract: Publication date: 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volumes 79–82
      Author(s): Qian Zhang , Bing Liu , Weige Zhang , Gui Jin , Zhaohua Li
      Water scarcity and stress have attracted increasing attention as water has become increasingly regarded as one of the most critical resources in the world’s sustainable development. The Water Poverty Index (WPI), an interdisciplinary but straightforward measure that considers water availability from both the bio-geophysical perspective and the socio-economic perspective of people’s capacity to access water, has been successfully applied at national, regional, and local levels around the world. However, the general assessment of water stress at a macro level over only a snapshot limits the understanding of the geographic differences in and dynamics of water stress; this will, in turn, mislead decision-makers and may result in improper water strategies being implemented. In addition, to date, the typologies and trajectories of water stress have been underexplored. To fill this knowledge gap, we examine the spatio-temporal patterns, trajectories, and typologies of water stress using an adapted WPI for six counties in Zhangye City, which lies within an arid region of China, in order to provide policy priorities for each county. The results of our assessment indicate that water stress has become more severe over time (2005–2011) in most of the counties in Zhangye City. The results also show a distinct spatial variation in water scarcity and stress. Specifically, the results for Shandan county reflect its progressive policies on water access and management, and this county is regarded as engaging in good water governance. In contrast, Ganzhou district has faced more severe water pressure and is regarded as practicing poor water governance. Typology results show that each county faces its own particular challenges and opportunities in the context of water scarcity and stress. In addition, the trajectory map reveals that none of the counties has shown substantial improvement in both water access and management, a finding that should draw decision-makers’ close attention.

      PubDate: 2015-06-26T14:37:28Z
  • A model of the generation of electromagnetic emissions detected prior to
    • Abstract: Publication date: Available online 16 March 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): M.K. Kachakhidze , N.K. Kachakhidze , T.D. Kaladze
      Recent satellite and ground-based observations prove that during the formative period of earthquakes VLF/LF and ULF electromagnetic emissions are observed in seismogenic areas. This work offers an original model of self-generated electromagnetic oscillations of local segments of the lithospheric origins of the emissions. In the paper, the seismogenic area is considered to be an oscillatory-distributed system. This model simplifies physical analyses of the nonlinear effects and qualitatively explains the mechanisms that generate very low frequency electromagnetic waves in the period prior to an earthquake.

      PubDate: 2015-06-26T14:37:28Z
  • Changes in animal activity prior to a major (M=7) earthquake in the
           Peruvian Andes
    • Abstract: Publication date: Available online 17 March 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Rachel A. Grant , Jean Pierre Raulin , Friedemann T. Freund
      During earthquake preparation geophysical processes occur over varying temporal and spatial scales, some leaving their mark on the surface environment, on various biota, and even affecting the ionosphere. Reports on pre-seismic changes in animal behaviour have been greeted with scepticism by the scientific community due to the necessarily anecdotal nature of much of the evidence and a lack of consensus over possible causal mechanisms. Here we present records of changes in the abundance of mammals and birds obtained over a 30day period by motion-triggered cameras at the Yanachaga National Park, Peru, prior to the 2011 magnitude 7.0 Contamana earthquake. In addition we report on ionospheric perturbations derived from night-time very low frequency (VLF) phase data along a propagation paths passing over the epicentral region. Animal activity declined significantly over a 3-week period prior to the earthquake compared to periods of low seismic activity. Night-time ionospheric phase perturbations of the VLF signals above the epicentral area, fluctuating over the course of a few minutes, were observed, starting 2weeks before the earthquake. The concurrent observation of two widely different and seemingly unconnected precursory phenomena is of interest because recently, it has been proposed that the multitude of reported pre-earthquake phenomena may arise from a single underlying physical process: the stress-activation of highly mobile electronic charge carriers in the Earth’s crust and their flow to the Earth’s surface. The flow of charge carriers through the rock column constitutes an electric current, which is expected to fluctuate and thereby emit electromagnetic radiation in the ultralow frequency (ULF) regime. The arrival of the charge carriers can lead to air ionization at the ground-to-air interface and the injection of massive amounts of positive airborne ions, known to be aversive to animals.

      PubDate: 2015-06-26T14:37:28Z
  • Identification of the meta-instability stage via synergy of fault
           displacement: An experimental study based on the digital image correlation
    • Abstract: Publication date: Available online 21 March 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Yan-Qun Zhuo , Jin Ma , Yan-Shuang Guo , Yun-Tao Ji
      In stick–slip experiments modeling the occurrence of earthquakes, the meta-instability stage (MIS) is the process that occurs between the peak differential stress and the onset of sudden stress drop. The MIS is the final stage before a fault becomes unstable. Thus, identification of the MIS can help to assess the proximity of the fault to the earthquake critical time. A series of stick–slip experiments on a simulated strike-slip fault were conducted using a biaxial servo-controlled press machine. Digital images of the sample surface were obtained via a high speed camera and processed using a digital image correlation method for analysis of the fault displacement field. Two parameters, A and S, are defined based on fault displacement. A, the normalized length of local pre-slip areas identified by the strike-slip component of fault displacement, is the ratio of the total length of the local pre-slip areas to the length of the fault within the observed areas and quantifies the growth of local unstable areas along the fault. S, the normalized entropy of fault displacement directions, is derived from Shannon entropy and quantifies the disorder of fault displacement directions along the fault. Based on the fault displacement field of three stick–slip events under different loading rates, the experimental results show the following: (1) Both A and S can be expressed as power functions of the normalized time during the non-linearity stage and the MIS. The peak curvatures of A and S represent the onsets of the distinct increase of A and the distinct reduction of S, respectively. (2) During each stick–slip event, the fault evolves into the MIS soon after the curvatures of both A and S reach their peak values, which indicates that the MIS is a synergetic process from independent to cooperative behavior among various parts of a fault and can be approximately identified via the peak curvatures of A and S. A possible application of these experimental results to field conditions is provided. However, further validation is required via additional experiments and exercises.

      PubDate: 2015-06-26T14:37:28Z
  • Glacier changes and their impacts on the discharge in the past
           half-century in Tekes watershed, Central Asia
    • Abstract: Publication date: Available online 31 March 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Baorong Xu , Zhixiang Lu , Shiyin Liu , Jing Li , Jiali Xie , Aihua Long , Zhenliang Yin , Songbing Zou
      The glacier is an important and stable water supply in Central Asia. Monitoring the change of glacier and understanding the impacts of glacier change on river discharge are critical to predict the downstream water availability change in future. Glacier changes were discussed and their impacts on river discharge were evaluated by hydrological modeling with a distributed hydrological model SWAT under two land use and land cover scenarios (1970 and 2007) in Tekes watershed, the most important source of water discharge to the Ili River. Compared to the glacier area of 1511km2 in 1970s it decreased by 332km2 in 2007, which resulted in the contribution the discharge from precipitation in the glacier area to the average annual discharge of the watershed changing from 9.8% in the period 1966–1975 to 7.8% in the period 2000–2008. In the month scale, with the decrease of glacier area, the distribution of the contribution of monthly discharge from precipitation in the glacier area to the total of the watershed changed from bimodal pattern to unimodal pattern. By linking a hydrological model to remote sensing image analysis and Chinese glacier inventories to determine glacier area change our approach in quantifying the impacts of glacier changes on hydrology at different scales, will provide quantitative information for stakeholders in making decisions for water resource management.

      PubDate: 2015-06-26T14:37:28Z
  • Evidence of non extensivity in the evolution of seismicity along the San
           Andreas Fault, California, USA: An approach based on Tsallis statistical
    • Abstract: Publication date: Available online 7 April 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): A. Efstathiou , A. Tzanis , F. Vallianatos
      We examine the nature of the seismogenetic system along the San Andreas Fault (SAF), California, USA, by searching for evidence of complexity and non-extensivity in the earthquake record. We use accurate, complete and homogeneous earthquake catalogues in which aftershocks are included (raw catalogues), or have been removed by a stochastic declustering procedure (declustered catalogues). On the basis of Non-Extensive Statistical Physics (NESP), which generalizes the Boltzmann–Gibbs formalism to non-equilibrating (complex) systems, we investigate whether earthquakes are generated by an extensive self-excited Poisson process or by a non-extensive complex process. We examine bivariate cumulative frequency distributions of earthquake magnitudes and interevent times and determine the size and time dependence of the respective magnitude and temporal entropic indices, which indicate the level on non-equilibrium (correlation). It is shown that the magnitude entropic index is very stable and corresponds to proxy b-values that are remarkably consistent with the b-values computed by conventional means. The temporal entropic index computed from the raw catalogues indicate moderately to highly correlated states during the aftershock sequences of large earthquakes, progressing to quasi-uncorrelated states as these die out and before the next large event. Conversely, the analysis of the declustered catalogues shows that background seismicity exhibits moderate to high correlation that varies significantly albeit smoothly with time. This indicates a persistent sub-extensive seismogenetic system. The degree of correlation is generally higher in the southern SAF segment, which is consistent with the observation of shorter return periods for large earthquakes. A plausible explanation is that because aftershock sequences are localized in space and time, their efficient removal unveils long-range background interactions which are obscured by their presence! Our results indicate complexity in the expression of background seismicity along the San Andreas Fault, with criticality being a very likely mechanism as a consequence of the persistent non-equilibrium inferred from the temporal entropic index. However, definite conclusions cannot be drawn until the earthquake record is exhaustively studied in all its forms.

      PubDate: 2015-06-26T14:37:28Z
  • Laboratory measurements on radon exposure effects on local environmental
           temperature: Implications for satellite TIR measurements
    • Abstract: Publication date: Available online 15 April 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Giovanni Martinelli , Andrzej Tomasz Solecki , Dagmara Eulalia Tchorz-Trzeciakiewicz , Magdalena Piekarz , Katarzyna Karolina Grudzinska
      Surface latent heat flux (SLHF) is proportional to the heat released by phase changes during solidification, evaporation or melting. Effects of SLHF on the earth’s surface could be measured by satellite techniques capable of measuring thermal infrared radiation (TIR). Recent studies have found a possible correlation between SLHF and earthquakes, hence satellite techniques are widely used in research into the possible link between SLHF and earthquakes. Possible fluctuations in SLHF values during seismic periods have been attributed to different causes, such as the expulsion from the ground of greenhouse gases or because of radon. In particular, ionization processes due to radon decay could lead to changes in air temperature. Laboratory experiments have been carried out to highlight the possible role of radon in the thermal environmental conditions of a laboratory-controlled atmospheric volume.

      PubDate: 2015-06-26T14:37:28Z
  • Temporal correlation patterns in pre-seismic electromagnetic emissions
           reveal distinct complexity profiles prior to major earthquakes
    • Abstract: Publication date: Available online 7 April 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Reik V. Donner , Stelios M. Potirakis , Georgios Balasis , Konstantinos Eftaxias , Jürgen Kurths
      In the last years, continuous recordings of electromagnetic emissions from geophysical observatories have been recognized to exhibit characteristic fluctuation patterns prior to some major earthquakes. To further evaluate and quantify these findings, this work presents a detailed assessment of the time-varying correlation properties of such emissions during the preparatory phases preceding some recent earthquakes in Greece and Italy. During certain stages before the earthquakes’ occurrences, the electromagnetic variability profiles are characterized by a marked increase in the degree of organization of fluctuations, which allow developing hypotheses about the underlying physical mechanisms. Based on the preparatory phases of selected seismic events, the information provided by different statistical properties characterizing complementary aspects of the time-varying complexity based on temporal correlations is systematically assessed. The obtained results allow further insights into different pre-seismic stages based on the variability of electromagnetic emissions, which are probably associated with distinct geophysical processes.

      PubDate: 2015-06-26T14:37:28Z
  • TEC variations over the Mediterranean before and during the strong
           earthquake (M=6.5) of 12th October 2013 in Crete, Greece
    • Abstract: Publication date: Available online 16 April 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): M.E. Contadakis , D.N. Arabelos , G. Vergos , S.D. Spatalas , M. Skordilis
      In this paper, the total electron content (TEC) data from eight global positioning system (GPS) stations of the EUREF network, provided by IONOLAB (Turkey), were analyzed using discrete Fourier analysis to investigate the TEC variations over the Mediterranean before and during the strong earthquake of 12th October 2013, which occurred west of Crete, Greece. In accordance with the results of similar analyses in the area, the main conclusions of this study are the following: (a) TEC oscillations in a broad range of frequencies occur randomly over an area of several hundred km from the earthquake and (b) high frequency oscillations (f ⩾0.0003Hz, periods T ⩽60m) may point to the location of the earthquake with questionable accuracy. The fractal characteristics of the frequency distribution may point to the locus of the earthquake with higher accuracy. We conclude that the lithosphere–atmosphere–ionosphere coupling (LAIC) mechanism through acoustic or gravity waves could explain this phenomenology.

      PubDate: 2015-06-26T14:37:28Z
  • Patterns of significant seismic quiescence on the Mexican Pacific coast
    • Abstract: Publication date: Available online 18 April 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): A. Muñoz-Diosdado , A.H. Rudolf-Navarro , F. Angulo-Brown , A.G. Barrera-Ferrer
      Many authors have proposed that the study of seismicity rates is an appropriate technique for evaluating how close a seismic gap may be to rupture. We designed an algorithm for identification of patterns of significant seismic quiescence by using the definition of seismic quiescence proposed by Schreider (1990). This algorithm shows the area of quiescence where an earthquake of great magnitude may probably occur. We have applied our algorithm to the earthquake catalog on the Mexican Pacific coast located between 14 and 21degrees of North latitude and 94 and 106degrees West longitude; with depths less than or equal to 60km and magnitude greater than or equal to 4.3, which occurred from January, 1965 until December, 2014. We have found significant patterns of seismic quietude before the earthquakes of Oaxaca (November 1978, Mw =7.8), Petatlán (March 1979, Mw =7.6), Michoacán (September 1985, Mw =8.0, and Mw =7.6) and Colima (October 1995, Mw =8.0). Fortunately, in this century earthquakes of great magnitude have not occurred in Mexico. However, we have identified well-defined seismic quiescences in the Guerrero seismic-gap, which are apparently correlated with the occurrence of silent earthquakes in 2002, 2006 and 2010 recently discovered by GPS technology.

      PubDate: 2015-06-26T14:37:28Z
  • WRF-chem sensitivity to vertical resolution during a saharan dust event
    • Abstract: Publication date: Available online 8 May 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): J.C. Teixeira , A.C. Carvalho , Paolo Tuccella , Gabriele Curci , A. Rocha
      The Saharan dust event that occurred between the 22nd and 30th of June 2012 influenced the atmospheric radiative properties over North Africa, the Iberian Peninsula, the Western Mediterranean basin, extending its effects to France and Southern England. This event is well documented in satellite imagery, as well as on the air quality stations over the Iberian Peninsula and the AERONET NASA network. In order to assess the effect of the model vertical resolution on the extinction coefficient fields, as a proxy to the particulate matter concentrations in the atmosphere, the WRF-Chem model was applied during this period over a mother domain with a resolution of 18km, covering Europe and North Africa. To this end five model setups differing in the number of vertical levels were tested. Model skills were evaluated by comparing the model results with CALIPSO and EARLINET LIDAR data. Results show that the model is able to simulate the higher level aerosol transport but it is susceptible to the vertical resolution used. This is due to the thickness of the transport layers which is, eventually, thinner than the vertical resolution of the model. When comparing model results to the observed vertical profiles, it becomes evident that the broad features of the extinction coefficient profile are generally reproduced in all model configurations, but finer details are captured only by the higher resolution simulations.

      PubDate: 2015-06-26T14:37:28Z
  • Streamflow variation due to glacier melting and climate change in upstream
           Heihe River Basin, Northwest China
    • Abstract: Publication date: 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volumes 79–82
      Author(s): Feng Wu , Jinyan Zhan , Zhan Wang , Qian Zhang
      Streamflow simulation is often challenging in mountainous watersheds because of incomplete hydrological models, irregular topography, immeasurable snowpack or glacier, and low data resolution. In this study, a semi-distributed conceptual hydrological model (SWAT-Soil Water Assessment Tool) coupled with a glacier melting algorithm was applied to investigate the sensitivity of streamflow to climatic and glacial changes in the upstream Heihe River Basin. The glacier mass balance was calculated at daily time-step using a distributed temperature-index melting and accumulation algorithm embedded in the SWAT model. Specifically, the model was calibrated and validated using daily streamflow data measured at Yingluoxia Hydrological Station and decadal ice volume changes derived from survey maps and remote sensing images between 1960 and 2010. This study highlights the effects of glacier melting on streamflow and their future changes in the mountainous watersheds. We simulate the contribution of glacier melting to streamflow change under different scenarios of climate changes in terms of temperature and precipitation dynamics. The rising temperature positively contributed to streamflow due to the increase of snowmelt and glacier melting. The rising precipitation directly contributes to streamflow and it contributed more to streamflow than the rising temperature. The results show that glacial meltwater has contributed about 3.25billionm3 to streamflow during 1960–2010. However, the depth of runoff within the watershed increased by about 2.3mm due to the release of water from glacial storage to supply the intensified evapotranspiration and infiltration. The simulation results indicate that the glacier made about 8.9% contribution to streamflow in 2010. The research approach used in this study is feasible to estimate the glacial contribution to streamflow in other similar mountainous watersheds elsewhere.

      PubDate: 2015-06-26T14:37:28Z
  • Impacts of land use and land cover changes on surface energy and water
           balance in the Heihe River Basin of China, 2000–2010
    • Abstract: Publication date: 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volumes 79–82
      Author(s): Xiangzheng Deng , Qingling Shi , Qian Zhang , Chenchen Shi , Fang Yin
      It is well known that there are huge land use and land cover changes (LUCC) all over the world in recent decades, and plenty of ensuing effect appeared on the energy and water balance. This study aims to analyze the impacts of land use and land cover changes on the energy and water balance in the Heihe River Basin of China during 2000–2010, and four key study sites with representative hydrological stations and dramatic LUCC in the past decades were selected to illustrate the responses of the energy and water balance to LUCC. First, LUCC of the Heihe River Basin from 2000 to 2010 was analyzed based on the interpretation of remote sensing images. Then a series of indicators of the energy and water balances were simulated with the Weather Research and Forecasting (WRF) model and corresponding land use and land cover data. Thereafter the impacts of LUCC on the surface energy and water balance were detected and analyzed. The spatial–temporal variance of the impacts of LUCC on energy and water balance in a typical arid inland river basin was specifically presented in following analysis. The results show that different land use/cover conversions result in various energy balances. During this process, the most significant impacts on surface energy balance occurred when grassland was converted to barren or sparsely vegetated land. As for water balance, the impact is measured with variations of precipitation, runoff and evapotranspiration induced by LUCC, which were also remarkable, although seasonal trends of the effects are similar among various land use/cover conversions during 2000–2010. At last, policy suggestions, e.g., shifting the water balance by LUCC to improve the water management, are given to conclude this study.

      PubDate: 2015-06-26T14:37:28Z
  • Physical and economic processes of water scarcity and water allocation for
           integrated river basin management
    • Abstract: Publication date: 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volumes 79–82
      Author(s): Xiangzheng Deng , R.B. Singh , Junguo Liu , Burak Güneralp

      PubDate: 2015-06-26T14:37:28Z
  • Two-scale analysis for environmental dispersion in a two-layer wetland
    • Abstract: Publication date: Available online 2 January 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Bin Chen , Lizhu Zhang , Tasawar Hayat , Ahmed Alsaedi , Bashir Ahmad
      Studies on environmental dispersion are essential for applications as water management. The two-scale perturbation analysis is applied in this paper to deduce the environmental dispersion model for the typical case of contaminant transport in two-layer wetland flows. The analysis follows the established theoretical framework on the basis of phase average and the concept of Taylor dispersion. By the obtained flow velocity distribution for the two-layer flow, the analytical expression for the environmental dispersivity is deduced and shown to be consistent with previous results by the concentration moment method, while with much simplifications on the expression for ignoring the less concerned time-dependent stage of the dispersivity.

      PubDate: 2015-06-26T14:37:28Z
  • Radar altimetry backscattering signatures at Ka, Ku, C, and S bands over
           West Africa
    • Abstract: Publication date: Available online 14 May 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): F. Frappart , C. Fatras , E. Mougin , V. Marieu , A.T. Diepkilé , F. Blarel , P. Borderies
      This study presents a comprehensive comparison of radar altimetry signatures at Ka-, Ku-, C-, and S-bands using SARAL, ENVISAT and Jason-2 data over the major bioclimatic zones, soil and vegetation types encountered in West-Africa, with an emphasis on the new information at Ka-band provided by the recently launched SARAL–Altika mission. Spatio-temporal variations of the radar altimetry responses were related to changes in surface roughness, land cover and soil wetness. Analysis of time series of backscattering coefficients along the West African bioclimatic gradient shows that radar echoes at nadir incidence are well correlated to soil moisture in semi-arid savannah environments. Radar altimeters are able to detect the presence of water even under a dense canopy cover at all frequencies. But only measurements at Ka-band are able to penetrate underneath the canopy of non-inundated tropical evergreen forests.

      PubDate: 2015-06-26T14:37:28Z
  • Parametric exponentially correlated surface emission model for L-band
           passive microwave soil moisture retrieval
    • Abstract: Publication date: Available online 15 May 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Tianjie Zhao , Jiancheng Shi , Rajat Bindlish , Thomas Jackson , Michael Cosh , Lingmei Jiang , Zhongjun Zhang , Huimin Lan
      Surface soil moisture is an important parameter in hydrology and climate investigations. Current and future satellite missions with L-band passive microwave radiometers can provide valuable information for monitoring the global soil moisture. A factor that can play a significant role in the modeling and inversion of microwave emission from land surfaces is the surface roughness. In this study, an L-band parametric emission model for exponentially correlated surfaces was developed and implemented in a soil moisture retrieval algorithm. The approach was based on the parameterization of an effective roughness parameter of Hp in relation with the geometric roughness variables (root mean square height s and correlation length l) and incidence angle. The parameterization was developed based on a large set of simulations using an analytical approach incorporated in the advanced integral equation model (AIEM) over a wide range of geophysical properties. It was found that the effective roughness parameter decreases as surface roughness increases, but increases as incidence angle increases. In contrast to previous research, Hp was found to be expressed as a function of a defined slope parameter m = s 2/l, and coefficients of the function could be well described by a quadratic equation. The parametric model was then tested with L-band satellite data in soil moisture retrieval algorithm over the Little Washita watershed, which resulted in an unbiased root mean square error of about 0.03m3/m3 and 0.04m3/m3 for ascending and descending orbits, respectively.

      PubDate: 2015-06-26T14:37:28Z
  • Various remote sensing approaches to understanding roughness in the
           marginal ice zone
    • Abstract: Publication date: Available online 15 May 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Mukesh Gupta
      Multi-platform based measurement approaches to understanding complex marginal ice zone (MIZ) are suggested in this paper. Physical roughness measurements using ship- and helicopter-based laser systems combined with ship-based active microwave backscattering (C-band polarimetric coherences) and dual-polarized passive microwave emission (polarization ratio, PR and spectral gradient ratios, GR at 37 and 89GHz) are presented to study diverse sea ice types found in the MIZ. Autocorrelation functions are investigated for different sea ice roughness types. Small-scale roughness classes were discriminated using data from a ship-based laser profiler. The polarimetric coherence parameter ρ HHVH , is not found to exhibit any observable sensitivity to the surface roughness for all incidence angles. Rubble-ridges, pancake ice, snow-covered frost flowers, and dense frost flowers exhibit separable signatures using GR-H and GR-V at >70° incidence angles. This paper diagnosed changes in sea ice roughness on a spatial scale of ∼0.1–4000m and on a temporal scale of ∼1–240days (ice freeze-up to summer melt). The coupling of MIZ wave roughness and aerodynamic roughness in conjunction with microwave emission and backscattering are future avenues of research. Additionally, the integration of various datasets into thermodynamic evolution model of sea ice will open pathways to successful development of inversion models of MIZ behavior.

      PubDate: 2015-06-26T14:37:28Z
  • Study on the association of green house gas (CO2) with monsoon rainfall
           using AIRS and TRMM satellite observations
    • Abstract: Publication date: Available online 16 May 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): R.B. Singh , M. Janmaijaya , S.K. Dhaka , V. Kumar
      Monsoon water cycle is the lifeline to over 60 per cent of the world’s population. Throughout history, the monsoon-related calamities of droughts and floods have determined the life pattern of people. The association of Green House Gases (GHGs) particularly Carbon dioxide (CO2) with monsoon has been greatly debated amongst the scientific community in the past. The effect of CO2 on the monsoon rainfall over the Indian–Indonesian region (8–30°N, 65°–100°E) is being investigated using satellite data. The correlation coefficient (R xy) between CO2 and monsoon is analysed. The R xy is not significantly positive over a greater part of the study region, except a few regions. The inter-annual anomalies of CO2 is identified for playing a secondary role to influencing monsoon while other phenomenon like ENSO might be exerting a much greater influence.

      PubDate: 2015-06-26T14:37:28Z
  • Seasonal drought predictability in Portugal using
           statistical–dynamical techniques
    • Abstract: Publication date: Available online 16 May 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): A.F.S. Ribeiro , C.A.L. Pires
      Atmospheric forecasting and predictability are important to promote adaption and mitigation measures in order to minimize drought impacts. This study estimates hybrid (statistical–dynamical) long-range forecasts of the regional drought index SPI (3-months) over homogeneous regions from mainland Portugal, based on forecasts from the UKMO operational forecasting system, with lead-times up to 6months. ERA-Interim reanalysis data is used for the purpose of building a set of SPI predictors integrating recent past information prior to the forecast launching. Then, the advantage of combining predictors with both dynamical and statistical background in the prediction of drought conditions at different lags is evaluated. A two-step hybridization procedure is performed, in which both forecasted and observed 500hPa geopotential height fields are subjected to a PCA in order to use forecasted PCs and persistent PCs as predictors. A second hybridization step consists on a statistical/hybrid downscaling to the regional SPI, based on regression techniques, after the pre-selection of the statistically significant predictors. The SPI forecasts and the added value of combining dynamical and statistical methods are evaluated in cross-validation mode, using the R 2 and binary event scores. Results are obtained for the four seasons and it was found that winter is the most predictable season, and that most of the predictive power is on the large-scale fields from past observations. The hybridization improves the downscaling based on the forecasted PCs, since they provide complementary information (though modest) beyond that of persistent PCs. These findings provide clues about the predictability of the SPI, particularly in Portugal, and may contribute to the predictability of crops yields and to some guidance on users (such as farmers) decision making process.

      PubDate: 2015-06-26T14:37:28Z
  • Socioeconomic impacts of hydropower development on the
           Yibin–Chongqing section, upper reaches of the Yangtze River
    • Abstract: Publication date: Available online 18 May 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Jing Ma , Yu Liu , Hao Wang , Deng Hua Yan , Ying Kang Lv , Zhaohui Yang
      The aim of this paper is to quantify the socioeconomic impacts of hydropower development to reflect its positive functions from multiple perspectives and dimensions. By applying the multi-regional Computable General Equilibrium (CGE) model to a case study of the Yibin–Chongqing section along the upper reaches of the Yangtze River, the analysis shows that hydropower development has outstanding benefits for the regional economy and livelihood improvement, as proved by various indicators including consumption, investment, GDP, employment, and income. Meanwhile, application of the CGE model provides an effective way to quantitatively assess the socioeconomic impact of hydropower and other clean energy development.

      PubDate: 2015-06-26T14:37:28Z
  • Geospace perturbations induced by the Earth: The state of the art and
           future trends
    • Abstract: Publication date: Available online 22 May 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): A. De Santis , G. De Franceschi , L. Spogli , L. Perrone , L. Alfonsi , E. Qamili , G. Cianchini , R. Di Giovambattista , S. Salvi , E. Filippi , F.J. Pavón-Carrasco , S. Monna , A. Piscini , R. Battiston , V. Vitale , P.G. Picozza , L. Conti , M. Parrot , J.-L. Pinçon , G. Balasis , M. Tavani , A. Argan , G. Piano , M.L. Rainone , W. Liu , D. Tao
      A systematic multi-parameter and multi-platform approach to study the slow process of earthquake preparation is fundamental to gain some insights on this complex phenomenon. In particular, an important contribution is the integrated analysis between ground geophysical data and satellite data. In this paper we review some of the more recent results and suggest the next directions of this kind of research. Our intention is not to detect a particular precursor but to understand the physics underlying the various observations and to establish a reliable physical model of the preparation phase before an impending earthquake. In this way, future investigation will search for suitable fore-patterns, which the physical model of multi-layers coupling predicts and characterizes by quasi-synchronism in time and geo-consistency in space. We also present alternative explanations for some anomalies which are not actually related to earthquakes, rather to other natural or anthropic processes.

      PubDate: 2015-06-26T14:37:28Z
  • Recursive cross-entropy downscaling model for spatially explicit future
           land uses: A case study of the Heihe River Basin
    • Abstract: Publication date: Available online 1 June 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Xinxin Zhang , Tatiana Ermolieva , Juraj Balkovic , Aline Mosnier , Florian Kraxner , Junguo Liu
      Downscaling methods assist decision makers in coping with the uncertainty regarding sustainable local area developments. In particular, they allow investigating local heterogeneities regarding water, food, energy, and environment consistently with global, national, and sub-national drivers and trends. In this paper, we develop a conceptual framework that integrates a partial equilibrium Global Biosphere Management Model (GLOBIOM) with a dynamic cross-entropy downscaling model to derive spatially explicit projections of land uses at 1-km spatial resolution from 2010 to 2050 relying on aggregate land demand projections. The fusion of the two models is applied in a case study in Heihe River Basin to analyze the extent of potential cropland, grassland, and unused land transformations, which may exacerbate already extensive water consumption caused by rapid expansion of irrigated agriculture in the case study region. The outcomes are illustrated for two Shared Socioeconomic Pathway scenarios. The kappa coefficients show that the downscaling results are in agreement with the land use and land cover map of the Heihe River Basin, which indicates that the proposed approach produces realistic local land use projections. The downscaling results show that under both SSP scenarios the cropland area is expected to increase from 2010 to 2050, while the grassland area is projected to increase sharply from 2010 to 2030 and then gradually come to a standstill after 2030. The results can be used as an input for planning sustainable land and water management in the study area, and the conceptual framework provides a general approach to creating high-resolution land-use datasets.

      PubDate: 2015-06-26T14:37:28Z
  • Aspects regarding the use of the INFREP network for identifying possible
           seismic precursors
    • Abstract: Publication date: Available online 4 June 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Paul Dolea , Octavian Cristea , Paul Vladut Dascal , Iren-Adelina Moldovan , Pier Francesco Biagi
      In the last decades, one of the main research directions in identifying seismic precursors involved monitoring VLF (Very Low Frequency) and LF (Low Frequency) radio waves and analysing their propagation characteristics. Essentially this method consists of monitoring different available VLF and LF transmitters from long distance reception points. The received signal has two major components: the ground wave and the sky wave, where the sky wave propagates by reflection on the lower layers of the ionosphere. It is assumed that before and during major earthquakes, unusual changes may occur in the lower layers of the ionosphere, such as the modification of the charged particles number density and the altitude of the reflection zone. Therefore, these unusual changes in the ionosphere may generate unusual variations in the received signal level. The International Network for Frontier Research on Earthquake Precursors (INFREP) was developed starting with 2009 and consists of several dedicated VLF and LF radio receivers used for monitoring various radio transmitters located throughout Europe. The receivers’ locations were chosen so that the propagation path from these VLF/LF stations would pass over high seismicity regions while others were chosen to obtain different control paths. The monitoring receivers are capable of continuously measuring the received signal amplitude from the VLF/LF stations of interest. The recorded data is then stored and sent to an INFREP database, which is available on the Internet for scientific researchers. By processing and analysing VLF and LF data samples, collected at different reception points and at different periods of the year, one may be able to identify some distinct patterns in the envelope of the received signal level over time. Significant deviations from these patterns may have local causes such as the electromagnetic pollution at the monitoring point, regional causes like existing electrical storms over the propagation path or even global causes generated by high-intensity solar flares. As a consequence, classifying these perturbations and minimizing them (when possible) would represent an important step towards identifying significant pattern deviations caused by seismic activities. Taken into consideration some of the issues mentioned above, this paper intends to present some aspects meant to improve the overall performance of the existing INFREP network. The signal-to-noise ratio improvement of the monitoring receiver may be achieved by relocating the antenna (or even the entire monitoring system if possible) in areas with less electromagnetic pollution within the VLF and LF bands. Other solution may involve replacing the existing electric “whip” antennas with magnetic loop antennas. Regarding the measuring method, long-term averaging of the received signal to reduce the electromagnetic noise should be carefully applied. If the averaging time is too long, there is a risk that, during a seismic event, the details of the received signal envelope would be lost. Moreover, this may reduce the possibility of making correlations between the monitored stations and INFREP receivers in case of sudden ERP (Effective Radiated Power) variations of the VLF/LF stations. For the same reason, the time synchronization of the recorded data using (for instance) GPS technology is highly recommended. Other aspects related to the overall performance improvement of the INFREP network consist of monitoring other VLF/LF stations such as the Krasnodar station (south of Russia), part of the ALPHA/RSDN-20 VLF navigation system, or the 77.5kHz DCF77 time signal transmitter (near Frankfurt am Main, Germany). Moreover, the installation of a new reception point in Romania (near Cluj-Napoca) for monitoring the Vrancea area (within the Carpathians Mountains) and the Adriatic region will provide complementary scientific data within the network.

      PubDate: 2015-06-26T14:37:28Z
  • A new approach to assessing the water footprint of hydroelectric power
           based on allocation of water footprints among reservoir ecosystem services
    • Abstract: Publication date: Available online 31 March 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Dandan Zhao , Junguo Liu
      Hydroelectric power is an important energy source to meet the growing demand for energy, and large amounts of water are consumed to generate this energy. Previous studies often assumed that the water footprint of hydroelectric power equaled the reservoir’s water footprint, but failed to allocate the reservoir water footprint among the many beneficiaries; dealing with this allocation remains a challenge. In this study, we developed a new approach to quantify the water footprint of hydroelectric power (WF h) by separating it from the reservoir water footprint (WF) using an allocation coefficient (ηh) based on the ratio of the benefits from hydroelectric power to the total ecosystem service benefits. We used this approach in a case study of the Three Gorges Reservoir, the world’s largest reservoir, which provides multiple ecosystem services. We found large differences between the WF h and the water footprint of per unit of hydroelectric production (PWF h) calculated using ηh and those calculated without this factor. From 2003 to 2012, ηh decreased sharply (from 0.76 in 2005 to 0.41 in 2012), which was due to the fact that large increases in the value of non-energy ecosystem services, and particularly flood control. In 2009, flood control replaced hydroelectricity as the largest ecosystem service of water from the Three Gorges Reservoir. Using our approach, WF h and PWF h averaged 331.0×106 m3 and 1.5 m3 GJ-1, respectively. However, these values would almost double without allocating water footprints among different reservoir ecosystem services. Thus, previous studies have overestimated the WF h and PWF h of reservoirs, especially for reservoirs that serve multiple purposes. Thus, the allocation coefficient should not be ignored when calculating the WF of a product or service.

      PubDate: 2015-04-02T12:15:22Z
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