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 Journal of Earth System ScienceJournal Prestige (SJR): 0.366 Citation Impact (citeScore): 1Number of Followers: 49     Open Access journal ISSN (Print) 0253-4126 - ISSN (Online) 0973-774X Published by Springer-Verlag  [2352 journals]
• Impact of Cartosat-1 orography on weather prediction in a high-resolution
NCMRWF unified model

• Abstract: The current study reports for the first time an application of orography from the Cartosat-1 satellite digital elevation model (DEM) generated at a source resolution of 30 m in a convection-permitting numerical weather prediction model. The effects of improvements in the representation of orography have been examined in the high-resolution regional National Centre for Medium Range Weather Forecasting (NCMRWF) Unified Model predictions for a heavy rainfall event over the city of Chennai. A time-lagged ensemble method is employed to account for the uncertainties associated with the initial conditions, which can better forecast extreme weather events than single forecasts. The simulations reveal that the predictions based on Cartosat-1 DEM capture the local details of the rainfall distribution better than the National Aeronautics and Space Administration shuttle radar topography mission DEM-based predictions, and better represent the orographic and thermal uplifting. The spatio-temporal patterns of the simulated rainfall over Chennai are superior in Cartosat-1 DEM-based simulations mainly due to the enhanced wind convergence and moisture transport. The present study reveals the role of mountains in the enhancement of heavy rainfall events over coastal cities and highlights the potential use of high-resolution orography in the improvement of the operational weather forecasting skill of the NCMRWF Unified Model.
PubDate: 2019-04-11

• Estimation of coda Q for the eastern Indian craton

• Abstract: We herein present new frequency-dependent coda- $$Q\,\,(Q_\mathrm{c})$$ relations ( $$Q_\mathrm{c} =Q_{\text {0}}f ^{n})$$ (frequency ranges between 2 and 18 Hz) for three regions of the eastern Indian craton (EIC), viz., the Singhbhum Odisha craton (SOC) and the Eastern Ghat mobile belt (EGMB), comprising the Mahanadi basin and the Chotanagpur granitic gneissic terrain (CGGT). The frequency-dependent coda- $$Q_\mathrm{c}$$ relations are obtained through the single backscattering model for coda waves ( $$Q_\mathrm{c})$$ of local earthquakes which are recorded on 15 three-component broadband seismograph stations in the regions. In this work, we pay special attention to test the lapse time ( $$t_\mathrm{L})$$ dependency of coda-Q ( $$Q_\mathrm{c})$$ estimates for the three regions. Lapse time signifies the sample area of the coda wave of the study region. Generally, the sample area increases with lapse time. To test the lapse time ( $$t_\mathrm{L})$$ dependency, nine different lapse time windows ( $$t_\mathrm{L})$$ from 10 to 90 s with 10 s interval are considered. On the ground of estimated poor correlation coefficients, only six lapse time windows ( $$t_\mathrm{L})$$ from 40 to 90 s with 10 s interval are considered. Our results suggest more heterogeneity in EGMB than that of the SOC and CGGT region. Estimates of $$Q_{\text {0}}$$ and n for the three regions of EIC (SOC, EGMB and CGGT) are found to be consistent with the results of $$Q_{\text {0}}$$ and n for mildly active less heterogeneous seismic zones in different parts of the world. By assuming entirely intrinsic attenuation characteristics, actual hazard parameters, i.e., extinction distance and anelastic attenuation coefficients are also computed for the three regions. The extinction distance ( $$L_\mathrm{e})$$ provides an idea of the distribution of scatterers in the lithosphere and anelastic attenuation coefficients signify the anelasticity of the medium, i.e., fluid movement and grain distribution. The estimate of extinction distance and attenuation coefficients suggests that for all three study regions, the upper mantle is relatively less heterogeneous and attenuation below 110–126 km depth is also comparatively lower. Coda Q indicates the degree of fracture and heterogeneity in the lithosphere related to seismicity. A higher estimate of $$Q_{\text {0}}$$ values in the Archaean SOC region and the Proterozoic CGGT region is found when compared with that of the sedimentary-rich EGMB. It can be inferred that seismically less active cratons in general comprise high $$Q_{\text {0}}$$ values, whereas the sedimentary-rich EGMB is more attenuative, characterised by a low coda $$Q_{\text {0}}$$ value. Moreover, it is found that the estimated $$Q_{\text {0}}$$ values for CGGT region are a little bit higher than that for the SOC region. This can be explained as a comparatively less disturbed and less heterogonous land mass that is present in the CGGT region as compared to the SOC region, which comprises different minerals, ore bodies, fault scarps and shear zones. The developed $$Q_\mathrm{c}$$ relation for the EIC region could be useful for the study of hazards and ground motion prediction.
PubDate: 2019-04-11

• Analysing the characteristic features of a pre-monsoon thunderstorm event
over Pune, India, using ground-based observations and WRF model

• Abstract: In the present work, the characteristic features and factors contributed to the formation of a typical pre-monsoon thunderstorm that occurred over Pune has been studied using various ground-based observations, such as microwave radiometer profiler, wind lidar and surface eddy covariance flux measurements along with weather research and forecast (WRF) model. Initially, the thermodynamic state of atmosphere, variation in fluxes, as well as convective updrafts and downdrafts associated with the thunderstorm event, has been studied using ground-based observations. Thermodynamic indices derived from ground-based microwave radiometer observations showed significant variation before, during and after the development of thunderstorm such as smaller humidity index and higher values of total total index and K-index during the storm. Convective available potential energy (CAPE) and equivalent potential temperature have also shown an increase prior to the event. It is noted that sensible heat flux is higher than latent heat flux before the initiation of storm, however, the latent heat flux increased significantly during the storm. Wind lidar-derived vertical velocities showed strong variation i.e., exceeding $$3 \,\hbox {m} \,\hbox {s}^{-1}$$ during the event. Signatures of veering effect indicated the transport of moisture to higher levels was noticed from the altitude variability of wind vector. Ground observations suggested strong crosswind wind shear, convergence of moisture that originated at elevated levels in the boundary layer and enhancement of moist static energy in the elevated layer above the surface was pre-storm characteristics that conducive for the storm enhancement. Secondly, the capabilities of a WRF model in simulating the storm development, structure and evolution have been verified. The WRF model was able to recreate major features of the environment in which the storm was developed. The model output was compared with ground observations, which showed that the model has well captured the sensible heat and friction velocity as that of observation compared to mixing ratio and latent heat. It is observed that the water vapour variation in the model is having a lag, about an hour, with that of observations. The detailed analysis of model output did not show triggering of a thunderstorm as noted in the observation at the same location, which may be probably due to model bias in the moisture transport or moisture convergence was weaker in the model.
PubDate: 2019-04-11

• Correlation of multiple deformation events in an area: Example from
schistose rocks of Lesser Himalayas, NW Pakistan

• Abstract: Integrated micro-, meso- and macro-structural investigations were carried out in the multiply deformed rocks of the Mula Gori area, northeastern Khyber Agency, Lesser Himalayas. These investigations revealed an intricate history of deformation events that have not been formerly recognised. These structural examinations show four successive deformations. These events were identified in the field as well as in oriented vertical thin sections. The first deformation event $$\hbox {D}_{1}$$ is preserved in the form of inclusion trails in garnet porphyroblasts of foliation intersection axis 1 (FIA 1) and the fold axis of the macroscopic fold indicates NW–SE orogeny-oblique shortening. The $$\hbox {D}_{2 }$$ event produced N–S trending foliations, fold axes and mineral lineations indicating E–W shortening. The $$\hbox {D}_{3}$$ is preserved as FIA 2 in garnet porphyroblast and E–W trending foliations, mineral lineations and fold axes in the field representing N–S shortening. The $$\hbox {D}_{4}$$ created NNW–SSE fabrics, which post-dates the main mantle thrust and the main boundary thrust, and likely resulted from the ENE–WSW bulk shortening related to development of the Hazara–Kashmir syntaxis.
PubDate: 2019-04-11

• Precision mapping of boundaries of flood plain river basins using
high-resolution satellite imagery: A case study of the Varuna river basin

• Abstract: Accurate demarcation of river basin boundaries is an important input for any programme connected with watershed management. In the present study, the boundary of the Varuna river basin is automatically derived using coarse- and medium-resolution digital elevation models (DEMs) of SRTM-30 m, ASTER-30 m, Cartosat-30 m, ALOS Palsar-12.5 m and Cartosat-10 m as well as manually through on-screen digitisation from a very high-resolution 1 m $$\times$$ 1 m remote sensing data available as Google Earth image. The study demonstrated the efficacy of on-screen digitisation from high-resolution Google Earth image supported by detailed field observations in the precision mapping of the place of origin of the Varuna River, its stream network and basin boundary when compared to the maps generated through automatic methods using DEMs of various resolutions. The Varuna river system takes its headwaters from the areas surrounding Umran and Dain ‘tals’ (shallow, large depressions/basins) but not from the west of Mau Aima town as has been previously reported.
PubDate: 2019-04-06

• Groundwater prospecting by the inversion of cumulative data of
Wenner–Schlumberger and dipole–dipole arrays: A case study at
Turamdih, Jharkhand, India

• Abstract: The present study deals with groundwater prospecting in hardrock terrain. Initially, the Wenner–Schlumberger array and the dipole–dipole array data have been acquired using Syscal Junior Switch-48. Furthermore, data acquired using both arrays have been merged using Prosys-II data handling software for the inversion of the cumulative data for possible mapping of water-bearing fracture rock masses with different structural distribution in a complex geological environment. The data have been analysed using RES2DINV software, based on the smoothness constrained least-square technique. Two numbers of 2D electrical resistivity tomography profiles (AA $$'$$ and BB $$'$$ ) have been selected over an official colony of the Turamdih uranium mine for groundwater prospecting, which is located at about 24 km west of Jaduguda, Jharkhand, India. High-resistivity features associated with a dyke-like structure have been delineated in both the profiles. Three low-resistivity features have been delineated as water saturated alluvium/aquifers in profile AA $$'$$ . A low-resistivity feature associated with the water-saturated fracture zone has been identified in profile BB $$'$$ , which is well correlated with the surficial location of an ephemeral channel at the bottom of the hill across the slope. It is observed that geoelectric sections generated by the inversion of cumulative data of both arrays provide superior results compared with the Wenner–Schlumberger and dipole–dipole arrays, separately.
PubDate: 2019-04-06

• The oldest record of the bivalve Dosinisca Dall and its implications

• Abstract: Certain species of Dosinia occurring in the Miocene of Kachchh and the Pliocene of Balochistan in reality belong to the subgenus Dosinisca (Veneridae, Dosiniinae). This subgenus was hitherto known from the Quaternary of the Western Pacific Zoogeographic Province. The present study reveals that the first occurrence of Dosinisca is in the Khari Nadi Formation (Aquitanian) of Kachchh, India. The faunal affinity of the Kachchh Basin with the Alpine–European region through the Tethys fauna until Oligocene came to an end in the Lower Miocene due to the uplifting of the Himalayas. Later, during Lower Miocene, faunal migration took place between Kachchh and the Barrow Island off the northwestern coast of Australia, through the East Indies and Timor Island. After Dosinisca thrived in the Indian Subcontinent during Lower Miocene, the receding of marine waters endangered its very existence in this part of the globe. It somehow survived in Balochistan during Pliocene due to an episode of marine transgression. However, it must have migrated eastwards to the East Indies to be eventually established in the Western Pacific Zoogeographic Province.
PubDate: 2019-04-06

• The mechanism of the bottom-crashing rockfall of a massive layered
carbonate rock mass at Zengziyan, Chongqing, China

• Abstract: Multiple carbonate cliffs are distributed in the karst mountain areas of southwestern China. The dynamic process and failure mechanism of rockfalls in the cliffs are complicated and undefined, and can be dangerous for settlements. Moreover, it is difficult to identify the potential for such failures before they occur. The rockfall of the Zengziyan cliff at Chongqing, China, is used as an example for studying this type of failure and to determine the developmental characteristics of rockfall, expounding on the evolving process from a cliff to an unstable rock mass through to rockfall. A fracturing–crashing failure mode is proposed, based on the evolutionary characteristics of damage development, compression-induced fracturing, rock mass crashing and overall rockfall. Finite difference numerical simulations were used to analyse and validate the failure mode of the Zengziyan cliff under three simulation conditions. The results of the simulations indicated that strength deterioration at the bottom of the cliff was the root cause of its fracturing–crashing rockfall. The outcomes of this paper could provide a new analytical model and theoretical basis for identifying and analysing similar types of geological disasters in the mountainous areas of southwestern China, and may provide valuable reference information for further mechanical analysis, stability evaluation and engineering prevention of unstable rock masses prone to a fracturing–crashing rockfall.
PubDate: 2019-04-06

• Petrographic controls on phosphorous distribution in coal seams of the
Jharia basin, India

• Abstract: In recent years, the international coking coal market is experiencing an acute shortage of coal supply which has caused a fluctuation in its price. Degradation of coke, in the blast furnace, is largely controlled by its inherent mineral matter. Phosphorous occurs in all coals in minor or trace amounts and is an important parameter to coal users, particularly in steel industries. The mode of occurrence and distribution of phosphorous minerals in 17 coal samples of the Jharia coal basin were investigated through petrographic examinations, technological characterisation and phosphorous distribution. The results reveal that the dull bands are eight times more enriched in phosphorous than the bright bands. The macerals of the inertinite group and mineral matter positively correlate with the phosphorous content, whereas vitrinite macerals have an apathetic correlation. The impact of the thermal alterations is localised and diminishes away from the contact of the intrusion. In contrast, the faulting does not appear to have any effect on the phosphorous content.
PubDate: 2019-04-06

• Audio-magnetotelluric investigation of Bakreswar Geothermal Province,
Eastern India

• Abstract: Bakreswar Geothermal Province (BGP) lies over the Archaean gneisses and schists formations. The heat flow and geothermal gradient of BGP are $$\sim$$ 230 mW/m $$^{2}$$ and $$95{^{\circ }}\hbox {C}/\hbox {km}$$ , respectively. The Bakreswar hot spring (BHS) ( $$23{^{\circ }}52^\prime 30^{\prime \prime }\hbox {N}$$ ; $$87{^{\circ }} 22^{\prime }30^{\prime \prime }\hbox {E}$$ ) is located over NNW–SSE trending fault. It lies in the eastern flank of BGP and is connected by Sone–Narmada–Tapti (SONATA) and deep-seated ONGC fault systems. Earlier studies indicated that the geothermal fluid flowed towards the same path as that of deep ONGC fault. In view of this, 24 audio-magnetotelluric soundings in the frequency range 10 kHz–10 Hz were conducted at one end of the deep ONGC fault, which is about 20 km northwest of BHS. The data analysis indicated that the data are internally consistent. Analysis of dimensionality and strike are indicative of complex conductivity structures. The 3D inversion of full impedance was performed to obtain a conductivity model of the study area and resulted in root mean square (RMS) for sites close to unity. The results have been discussed by extracting cross-section along 3 to 7 profiles (four of the profiles are perpendicular to strike, whereas three profiles were oblique to the strike direction and are perpendicular to east–west trending ONGC faults). Several low conducting zones are observed in the profiles drawn parallel and perpendicular to the strike. These common conductors show consistent model features but modified resistivity and dimension. Depth slices from 200 to 1400 m suggest that the conductors in the northern part of the study area are deeper than the conductors in the south. The study area is dominated by several shallow conductors which coincide with several fractures present in the study area. The conductors are surrounded by a resistive feature that can act as an impermeable bed and probably restricts the flow of water within the zone. The four major conductors along the oblique profiles (profiles perpendicular to deep ONGC fault) coincide with deep ONGC fault, through which probably the geothermal fluid flows.
PubDate: 2019-04-03

• Illite crystallinity index from the Mesoproterozoic sedimentary cover of
the Kaladgi basin, southwestern India: Implications on crustal depths of
subsidence and deformation

• Abstract: The grade of metamorphism and thermal maturity of the Mesoproterozoic Bagalkot Group in the Kaladgi basin of southwestern India has been determined using the illite crystallinity (IC) index. IC index was determined from the argillite samples of four stratigraphic levels viz., Ramdurg Formation (basal unit), Yargatti Formation (intermediate lower unit), Yadahalli Formation (intermediate upper unit) and Hoskatti formation (upper unit). IC index (Kubler equivalent) values range between $$0.54{^{\circ }}\Delta 2\theta$$ and $$0.24{^{\circ }}\Delta 2\theta$$ (in a set of 37 samples) and indicate a deep diagenetic to high anchizone metamorphic grade within a temperature range of $$\sim$$ 180 to 300 $${^{\circ }}\hbox {C}$$ . The Mesoproterozoic sedimentary cover of the Kaladgi basin is deformed due to southerly directed gravity gliding of the cover over the basement. The general variation of the IC index along and across the basin as indicated by the distribution of IC index values and isocryst contour patterns is due to the combined effect of deformation and variable subsidence of the Mesoproterozoic cover of the basin. Considering an average Mesoproterozoic geothermal gradient of $$35{^{\circ }}\hbox {C/km}$$ , the crustal depth of deformation and/or subsidence of the Mesoproterozoic cover up to the sample point is estimated to vary between 5.14 and 8.57 km.
PubDate: 2019-04-03

• Modelling of strong motion generation areas for a great earthquake in
central seismic gap region of Himalayas using the modified semi-empirical
approach

• Abstract: Over the past decades, strong motion generation areas (SMGAs) have received significant attention in the modelling of high-frequency records. Herein, we propose the source model for a scenario earthquake ( $$M_{\mathrm{w}}$$ 8.5) in the central seismic gap region of Himalayas. On the rupture plane, three SMGAs have been identified. Further, SMGA parameters are evaluated using available empirical relations. The spatiotemporal distribution of aftershocks is utilised to locate these SMGAs on the rupture plane. Further, the modified semi-empirical technique (MSET) is used to simulate the strong motion records. It has been observed that the study area can expect peak ground acceleration of $${>}\hbox {100 cm/s}^{2}$$ and its distribution is mainly affected by the location of nucleation point in the rupture plane. Furthermore, the estimated peak ground acceleration (PGA) values are comparable with the earlier studies in the region. This confirms the robustness of generated rupture model with three SMGAs and the reliability of MSET to simulate high-frequency records.
PubDate: 2019-04-02

• Multi-model assessment of trends, variability and drivers of terrestrial
carbon uptake in India

• Abstract: A multi-model-based assessment is made to assess the trends and variability in the land carbon uptake in India during the period 1901–2010. Data from nine models, used in a recent land surface model inter-comparison project called TRENDY, are used for this purpose. Our analysis is focused on the trends and variability in the net primary productivity (NPP), net ecosystem productivity (NEP) and net ecosystem exchange (NEE). The multi-model mean NPP shows a positive trend of 2.03% per decade during this period. The NEP, which is the difference between NPP and heterotrophic respiration, has a mean value of $$-\,0.138\,\pm \,0.086\,\hbox {Pg}\,\hbox {C}\,\hbox {yr}^{-1}$$ over this region. According to our analysis of TRENDY multi-models, the inter-annual variation in NPP and NEP is strongly driven by precipitation, but remote drivers such as El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) do not have a strong influence. The water use efficiency (WUE) shows an increase of about 25% over the 110-yr period. Our multi-model-based estimate of the cumulative NEE is $$0.613\,\pm \,0.1\,\hbox {Pg} \,\hbox {C}$$ during 1901–2010, indicating that the Indian terrestrial ecosystem was neither a strong source nor a significant sink during this period. However, we caution that our conclusion is based on a limited set of offline land models, and the results presented here have large uncertainties due to model resolution and parameterisation of various land surface processes, the inadequate validation procedures and the use of limited number of models and land use change data sets. Further investigations using more observational data, rigorous validation using extensive observational data sets and a set of comprehensive coupled models that include several feedbacks between land, atmosphere, ocean and the cryosphere are needed to assess the robustness of our results.
PubDate: 2019-04-02

• An approach to simulate the climate-driven streamflow in the data-scarce
mountain basins of Northwest China

• Abstract: With global warming, the inland river basin in the arid region of Northwest China is facing a serious water supply situation. The headwater basin of the inland river is located in the high-altitude mountainous region, and there are few meteorological observation sites, so it is difficult to apply distributed hydrological models and other models based on the physical mechanism of runoff generation to evaluate climate change and its impact on streamflow. To simulate the climate-driven streamflow in data-scarce mountain basins of Northwest China, we developed an integrated approach by using downscaled reanalysis data, Mann–Kendall test, ensemble empirical mode decomposition and backpropagation artificial neural networks together with the weights connection method. We validated the approach in the Kaidu River basin located in the Tianshan mountains. The results showed that the streamflow increased 12.9% by $$2.5 \times 10^{8}\,\hbox {m}^{3}$$ per decade with the warm and wet climate, while the average annual temperature increased 5.2% at a rate of $$0.3{^{\circ }}\hbox {C}$$ per decade and the precipitation increased 37.3% at a rate of 16.4 mm per decade during the period from 1980 to 2015. The impact of temperature variability on streamflow was 44.21 ± 2.08% and the impact of precipitation variability on streamflow was 55.79 ± 2.08%.
PubDate: 2019-04-02

• Flash flood susceptibility modelling using geomorphometric approach in the
Ushairy Basin, eastern Hindu Kush

• Abstract: This study focuses on flash flood susceptibility modelling using geomorphometric ranking approach in the Ushairy Basin. In the study area, flash floods are highly unpredictable and the worst hydrometeorological disaster. An advanced spaceborne thermal emission and reflection radiometer global digital elevation model was used as input data in a geographic information system environment to delineate the target basin. A total of 17 sub-basins were delimited using a threshold of $$4 \hbox {km}^{2}$$ . The attribute information of each sub-basin was analysed to compute the geomorphometric parameters by applying Hortonian and Strahler geomorphological models. The results were analysed and categorised into five classes using statistical techniques, and the rank score was assigned to each class of all parameters depending on their relation with flash flood risk. In this study, 16 parameters were analysed to quantify the geomorphometric number of each sub-basin depicting the degree of flash flood susceptibility. The geomorphometric number of each sub-basin was linked to the geo-database for spatial visualisation. The analysis reveals that extremely high, very high, high and moderate sub-basins susceptible to flash floods were spread over an area of 55%, 8.5%, 23.7%, and 11.5%, respectively. It was found that out of total settlements, 53% are located in the extremely highly and very highly susceptible sub-basins. In the study area, the upper reaches are characterised by snow-covered peaks, steep slopes and high drainage densities ( $${>}1.7 \hbox { km/km}^{2})$$ . The analysis further indicated that the flash flood susceptibility increases with the increase in area, relief and relief ratio of the sub-basins. Model accuracy was assessed using primary data regarding past flood damages and human fatalities. Similarly, socio-demographic conditions of each sub-basin were also compared and linked to the extent of flash flood susceptibility. This study may assist the district government and district disaster management authority of Dir upper to initiate flood risk reduction strategies in highly susceptible zones of the Ushairy Basin.
PubDate: 2019-04-02

• Temporal and spatial characteristics of droughts and floods in northern
China from 1644 to 1911

• Abstract: This study analyses the temporal and spatial distributions of droughts and floods in northern China during the Qing Dynasty (1636–1912), with data ranging from 1644 to 1911, or nearly the entire dynastic period. Variations in the intensities of droughts and floods are investigated across different timescales and with respect to their spatial variation. The impacts and physical mechanisms of solar activity as well as surface temperatures of the Pacific Ocean on drought and flood intensities in northern China are analysed using a cross-wavelet method. The results reveal periodicities on scales of 10–11, 20–22, 45–50 and 90–100 yrs. Seven rapid changes are found on the 10-yr scale and four are found on the 30-yr scale. Analysing the spatial distribution of drought and flood intensities, we found a trend of decreasing precipitation from east to west. Precipitation over the Shandong region, which is in the eastern part of the study area, is significantly higher than that of the other regions, which may be explained by its coastal location and the resultant rich water vapour content of the atmosphere. Analyses of cross-wavelet power spectra and coherence spectra among the different drought and flood intensities and the Niño3 regional sea surface temperature (SST) index series and sunspot series indicate significant correlations between the drought and flood series and the Niño3 SST index series at scales of 2–4 and 8–12 yrs, and the phase difference differs across the different timescales. Furthermore, the drought and flood series and the sunspot series are closely correlated at a scale of 8–14 yrs.
PubDate: 2019-04-02

• Evaluation of ambient air quality in Dehradun city during 2011–2014

• Abstract: The variations in the ambient concentrations of particulate matter (SPM and $$\hbox {PM}_{10}$$ ) and gaseous pollutants ( $$\hbox {SO}_{2}$$ and $$\hbox {NO}_{2}$$ ) at Clock tower (CT), Rajpur road (RR) and Inter State Bus Terminal (ISBT) station in Dehradun city, Uttarakhand, India are analysed for the period of 2011–2014. Mean concentrations are observed to be higher during pre-monsoon season as compared to the winter and monsoon. $$\hbox {PM}_{10}$$ and SPM concentrations with maximum values of $$203\pm 23$$ and $$429\pm 49\,\upmu \hbox {g m}^{-3}$$ , respectively, during winter, are found to exceed the national standards by factors of 2 and 3. Winter-time elevated pollution in Dehradun is attributed to the lower ventilation coefficient (derived from Era interim model fields) and minimal precipitation. Nevertheless, the $$\hbox {SO}_{2}$$ and $$\hbox {NO}_{2}$$ levels are observed to be within the criteria notified by the Central Pollution Control Board (CPCB), India. Correlation analysis shows profound impacts of the meteorology and local dynamics on the observed variations in observed trace species. Additionally, the stronger inter-species correlation variations ( $$r=0.79$$ for $$\hbox {SO}_{2}$$ with $$\hbox {NO}_{2}$$ , and $$r=0.89$$ for $$\hbox {PM}_{10}$$ with SPM), which may suggest their origin from common sources. Analysis of ‘Air Quality Index (AQI)’ variations indicates unhealthy atmospheric conditions near the major city centers and bus station. More observations in the region are highly desirable to understand the dispersion of the enhanced pollution in the Dehradun valley.
PubDate: 2019-04-02

• Comparison of coastal hydrodynamics in different energy regime coasts
along southwest coast of India

• Abstract: Study of the complex physical processes of beach-nearshore system helps to understand the coastal processes and facilitate coastal planning and management. Since the SW coast of India has very dynamic and contrasting hydrodynamic features, the Veli–Varkala stretch of southern Kerala (SK) and Munambam–Chettuwa sector of central Kerala (CK) were selected for a comparative study of their hydrodynamics. SK is a high wave energy coast compared to CK. The contrasting wave energy regimes result from the differences in the inner shelf slope and shoreline orientation. However, just as in the case of SK, waves and wave induced littoral processes are the dominant driving forces in the coastal processes of CK too. Due to the favorable hydrodynamic and sedimentological characteristics, mudbanks set in at different locations of CK affecting the coastal processes of the locations of its occurrence. Mudbanks do not occur along the SK due to the unfavorable sedimentological features. Artificial morphologies such as seawalls, groins, harbour breakwaters have a great role for coastal processes along both the sectors. The long term shoreline change along the SK and CK can be linked to the contrasting characteristics of longshore sediment transport along the coasts.
PubDate: 2019-04-02

• Relative impact of recent climate and land cover changes in the Godavari
river basin, India

• Abstract: The Godavari river basin (GRB), the second largest river basin (312,800  $$\hbox {km}^{2}$$ ) in India, was considered in this study to quantify the relative hydrological impact of recent land cover (LC) changes and rainfall trends using the variable infiltration capacity hydrologic model. Three scenarios, namely, (i) LC change, (ii) climate change and (iii) LC and climate changes, were considered to isolate the hydrological implications of the LC changes from those of climate change. Results revealed that evapotranspiration is predominantly governed by LC change and that small changes in rainfall cause greater changes in the runoff. Although the spatial extent of LC change is higher, the climate change is the dominant driver of hydrological changes within the GRB. Thus, climate projections are the key inputs to study the impact on the river basin hydrology. The results provide insights into the impacts of the climate and LC changes on the basin. The methodology and results of the present study can be further considered for water resource planning within the river basin in view of the changing environment.
PubDate: 2019-04-02

• Seasonal and annual variation of AIRS retrieved $$\hbox {CO}_{{2}}$$ CO 2
over India during 2003–2011

• Abstract: The present study shows spatio-temporal variability in carbon dioxide $$(\hbox {CO}_{2})$$ in the mid-tropospheric region over India (0–32 $$^{\mathrm{o}}\hbox {N}$$ , 60–100 $$^{\mathrm{o}}\hbox {E}$$ ) during 2003–2011. The $$\hbox {CO}_{2}$$ data used in the study is retrieved from Atmospheric Infra-Red Sounder (AIRS). Analysis of 9 yrs of data shows that the $$\hbox {CO}_{{2}}$$ exhibits a linear increasing trend of 2.01 ppm/year. Besides displaying the linear increasing trend, data show strong seasonal and annual variability. Concentration of $$\hbox {CO}_{{2}}$$ is observed to be highest around April–May (summer months), which decreases by 4–5 ppm during the monsoon months. Seasonal decrease in $$\hbox {CO}_{2}$$ concentration appeared to be influenced by the monsoonal activity. Low OLR (proxy of convection) associated with high rainfall during summer monsoon via increasing vegetation index (NDVI) appears to be the primary cause for the seasonal decrease in $$\hbox {CO}_{{2}}$$ through photosynthesis. Correlation coefficient between $$\hbox {CO}_{{2}}$$ and NDVI is of the order of –0.90 suggesting vegetation as a seasonal sink of $$\hbox {CO}_{{2}}$$ . Decrease in $$\hbox {CO}_{{2}}$$ concentration takes place at a delay of 2–3 months of rainfall. However, convection seems to be another component, which causes uplifting of $$\hbox {CO}_{{2}}$$ during dry summer (April and May) making high concentration in the mid-troposphere as shown by increase in the planetary boundary layer (PBL) height in this period. Eastward propagating intra-seasonal oscillations with period 30–40 days in OLR anomalies are found to modulate (with a fluctuation of 1–2 ppm) mid-tropospheric $$\hbox {CO}_{{2}}$$ . Analysis of seasonal anomalies in $$\hbox {CO}_{{2}}$$ over four different regions (northern, southern, western and eastern) of India is also being investigated. The regional variability of $$\hbox {CO}_{2}$$ in northern region show marginal larger values suggesting more anthropogenic activities especially during late winter.
PubDate: 2019-03-28

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