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- Impact of microphysics schemes on prediction of an extreme heavy rainfall
event over the Democratic People’s Republic of Korea: a case study using
WRF model-
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Abstract: The Kumchon region on the midlands of the Korean peninsula experienced the extreme rainfall on 29 August 2018 during the East Asian Summer Monsoon. In the present study, we investigated the sensitivity of this rainfall simulation of the Weather Research and Forecasting (WRF) model to the microphysics schemes. To this end, numerical simulations were performed for two different initial conditions using the WRF model with the grid resolution of 3 km and the different microphysics schemes (Lin, WDM6, Thompson, and Morrison). The initial conditions with two different initialization times were used to obtain a robust result. The model results were compared with the available surface observations. Our results of sensitivity simulations show that the microphysics are able to capture the observed rainfall pattern, but their skills are different significantly due to variation in mixing ratios of microphysics categories and associated dynamic and thermodynamic parameters. Compared to the observation, the Lin scheme displayed the best agreement in terms of the spatiotemporal distribution of heavy rainfall, while the performance of WDM6 scheme was the worst, for two initialization times. Model results suggested that the Lin scheme captured the spatiotemporal distribution of the different microphysics categories, and dynamic and thermodynamic parameters related to the intense rainfall event well. These results will be helpful to understand how the cloud microphysics affect rainfall prediction in the WRF model, and improve the forecast skills for heavy rainfall over the study region.
PubDate: 2023-06-05
- Role of urban boundary layer dynamics and ventilation efficiency in a
severe air pollution episode in Tehran, Iran-
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Abstract: Tehran faces a significant health challenge due to severe air pollution episodes during wintertime, which are associated with high concentrations of fine particulate matter with a diameter less than 2.5 µm (PM2.5). In this study, we investigated meteorology conditions of one of the severe air pollution episodes, occurred from 27th December 2020 to 15th January 2021, using the Weather Research and Forecasting (WRF) model. To gain insights into this episode, we also modeled a clean episode for comparison. Model validation of land surface temperature using remote sensing showed acceptable performance as well as ground observations for other parameters. We then calculated the ventilation coefficient (VC) from the WRF outputs and analyzed the results statistically. Results indicate the severe reduction in both VC and planetary boundary layer height (PBLH) during the polluted episode. We further linked the decrease in PBLH and VC of the polluted episode to a high-pressure system above 1020 hPa. In contrast, the results for the clean episode indicate that the low-pressure system as low as 1010 hPa led to higher PBLH and VC than during the polluted episode. This low-pressure system favors the reduction of PM2.5 levels to lower than 21 μgm−3.
PubDate: 2023-05-27
- Structural characteristics of typhoons Jebi (2018), Faxai (2019), and
Hagibis (2019)-
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Abstract: In recent years, Japan has experienced substantial damage from three intense typhoons: Jebi (2018), Faxai (2019), and Hagibis (2019). In this study, we provide a detailed description of the structure and synoptic environments of these typhoons, with particular focus on their frontal nature, temporal evolutions of the phase-space parameters, and the synoptic environments during their lifecycles. All three typhoons underwent phase changes at some point during their lifecycle before transitioning into extratropical cyclones. We found that their maximum intensities, as indicated by their maximum wind speed and minimum central pressure, occurred shortly after they transitioned from a cold-core to a warm-core structure. These typhoons displayed strong low-level convergence and upper-level divergence, along with favorable environmental conditions for strong convection before transitioning to extratropical cyclones. Our analysis suggests that the strong Typhoons Jebi and Hagibis had asymmetric structures with either deep warm or deep cold cores, whereas the relatively weak Typhoon Faxai had a symmetric deep warm core structure. Overall, our study provides valuable insights into the characteristics of intense typhoons and their transition to extratropical cyclones.
PubDate: 2023-05-22
- How much does a high-resolution global ensemble forecast improve upon
deterministic prediction skill for the Indian summer monsoon'-
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Abstract: The global Ensemble Prediction System (EPS) at NCMRWF (NEPS-G) comprises of 22 perturbed members in addition to the control (CNTL) member at 12 km horizontal resolution. Running this state-of-the-art ensemble configuration employs large computational resources compared to a deterministic system; hence it is crucial to determine if and to what extent it enhances the prediction skill of forecasts over the Indian region. In this study, we attempt to quantify the improvement in the skill of NEPS-G relative to the deterministic forecast for the 2018 Indian summer monsoon season. The ensemble mean shows substantially reduced forecast errors in the monsoon precipitation when verified against the Integrated Multi-satellite Retrievals for Global Precipitation Measurement (IMERG) data. NEPS-G mean demonstrates an improved skill for forecasts of moderate rainfall categories based on Peirce’s skill score, probability of detection and critical success index. The ensemble mean also shows an enhanced forecast skill at longer lead times, based on the anomaly correlation coefficient for both zonal winds at 850 hPa and precipitation. The model tends to underpredict very light precipitation and overpredict light precipitation. The Symmetric Extremal Dependence Index indicates a reasonable fidelity of the model in predicting heavy to very heavy rainfall. The continuous ranked probability score for NEPS-G is much lower than the mean absolute error of the CNTL forecast. The Relative Operating Characteristic curve of the ensemble distribution relative to CNTL further illustrates the value-addition by NEPS-G model to forecasts at longer lead times. Thus, through this study, the use of large computational resources for running the high-resolution NEPS-G is proved to be justified as it produces more reliable forecasts with longer lead times.
PubDate: 2023-05-17
- Lightning activity and Convective Available Potential Energy during
different phases of Indian summer monsoon season over central region of
India-
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Abstract: Present work addressed the variability of lightning flash count and persistence of Convective Available Potential energy (CAPE) during onset-withdrawal and active-break phases of Indian southwest monsoon (ISM) over central India region for the period 2014–2019. We have observed that higher lightning activity is during the prior to onset phase (June) period as well withdrawal phase (September–October) of Indian southwest monsoon season. During the break phase (mid-monsoon months, July and August), the monsoon trough shifts northwards; as a result, lightning activity does not cease totally and some lightning activity is still observed over study region. It is noticed that position of monsoon trough play an important role in the lightning activity and CAPE. The analysis clearly suggests high CAPE is a necessary condition for formation of thunderstorms during ISM period (June to September). From the station based CAPE data, it is seen that lightning activity is higher at a station Nagpur (close to the monsoon trough region) compared to a station Hyderabad (far away from monsoon trough). Further, the monsoon trough region remains conditionally unstable which generates lightning producing storms over the study region during monsoon season. Observations suggest that when monsoon trough is strong, entrainment of cold and dry air in the lower level from north of monsoon trough interact with warm and moist air from south of monsoon trough and can make the atmosphere conditionally unstable that helps in formation of thunderstorms over the study region during ISM.
PubDate: 2023-05-13
- Influence of tidal state on air temperature through penetrating sea breeze
front in Seoul in summer-
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Abstract: We examine the influence of tidal flats on the daily maximum air temperature in Seoul related to the penetration of sea-breeze front (SBF) using meteorological station data of summer over 10 years (2010–2019). The penetration of SBF at Seoul is detected using an objective SBF detection algorithm. 491 (53%) of the 920 days are classified as those with SBF passage on the coast. The SBF arrives in Seoul on 87% of sea breeze days on the coast. The passage time of the SBF in Seoul peaks between 1400 and 1600 LST, while the traveling time of SBF from the coast to Seoul peaks between 3 and 4 h. The cooling effect of sea breeze in Seoul is examined using the sea-breeze cooling capacity. We divide the sea-breeze days in Seoul into three groups in terms of the arrival time of the SBF in Seoul: before 1200 LST, between 1200 and 1500 LST, and after 1500 LST. All three groups show the cooling effect of sea breeze, which is greatest in the group where the SBF arrives before 1200 LST. The relationship between the tidal state and daily maximum temperature in Seoul is examined. Summer days are divided into four groups depending on the tidal state in the morning (0800–1200 LST) and ambient flow direction. The tidal effect on the daily maximum temperature in Seoul is tested at a significant level of 10% using a two-sample t test for onshore and offshore flows. A significant difference (p = 0.086) is observed for offshore flows, showing a higher daily maximum temperature in the low-tide group in the morning (LTM) than in the high-tide group in the morning (HTM). The passage rate of the SBF at Seoul in the LTM is less than that in the HTM for offshore flows. A weaker sea-breeze forcing and longer distance between the water boundary and Seoul in the LTM could prevent the inland penetration of the SBF, increasing the daily maximum temperature in Seoul.
PubDate: 2023-05-10
- Comparing GlobCurrent dataset with numerical results from a
high-resolution implementation of the POLCOMS-WAM coupled system under a
strong gap wind over the Gulf of Tehuantepec-
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Abstract: GlobCurrent provides a variety of datasets aiming to describe global ocean circulation, especially when dealing with large-scale phenomena. It includes surface Stokes drift and geostrophic, Ekman, and total (geostrophic plus Ekman) currents. GlobCurrent uses the CNES-CLS13 mean dynamic topography estimation as well as data from sea surface drifters and wind reanalysis to improve the computation of ocean currents from altimetry data, which represents a significant advance in describing the total ocean current. The aim of this work is to compare the surface GlobCurrent estimates with a coupled ocean–wave numerical simulation (POLCOMS-WAM), drifting buoys, and altimeter observations when dealing with a Tehuano event, i.e., intense (larger than 20 m s \(^{-1}\) ) and short duration (around 3–5 days) low-level winds blowing over the Gulf of Tehuantepec, Mexico. There is a good agreement between the wind-driven currents (Ekman currents plus Stokes drift) field from GlobCurrent and that estimated by POLCOMS–WAM, with the largest magnitudes \(\sim \) 0.8 m s \(^{-1}\) in the region influenced by the highest winds’ speed. The geostrophic circulation patterns in the Gulf of Tehuantepec are similarly reproduced by GlobCurrent and POLCOMS-WAM. However, some differences were observed in the presence of an anticyclonic eddy located in the western part of the study area. Numerical results exhibit a more symmetrical eddy with geostrophic current speeds that, in agreement with along-track observations, exceed the 1 m s \(^{-1}\) . Instead, the geostrophic eddy in GlobCurrent shows velocities of about 0.8 m s \(^{-1}\) . As observed through drifting buoys in 2000, numerical results show that the anticyclonic eddy west of the GoT has strong ageostrophic currents related to a cyclogeostrophic balance, which is not included in GlobCurrent. This regional case study provides a guideline for future improvements of GlobCurrent products, in particular for the estimation of geostrophic and total currents.
PubDate: 2023-05-09
- Spatio-temporal changes in sunshine duration over Iran: impact of physical
geographic components-
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Abstract: Current global emphasis is on finding and stimulating clean and renewable energy sources most suitable to given countries or regions. Iran as a country has particularly great potential for using solar energy given the relatively long daily sunshine duration. But understanding sunshine duration (i.e. solar energy potential) requires relevant spatio-temporal knowledge for both the recent past and future decades. We thus present a quantitative perspective on Iran's sunshine duration for the period 1981–2018 (based on station data) and future decades 2041–2080 (based on two modeled scenarios: RCP4.5 and RCP8.5). As might be expected, the findings demonstrate a variety of spatial and temporal changes in sunshine duration for coming decades, in part due to direct or indirect impacts associated with climate change. However, given that physical geographic factors (latitude, longitude, distance from permanent water bodies, elevation) influence sunshine duration across sub-regions of Iran, the effects of these factors are investigated for both the recent-past and future decades. Of these factors, the largest share of influence is latitude (58%), but this will decrease in share of influence to 53% in coming decades. In contrast, although longitude has had a small share of influence in recent decades (7.5%), its share of influence is projected to increase to 13.10% due to climate change by 2061 to 2080.
PubDate: 2023-05-09
- Trend analysis of hydro-meteorological variables of Islamabad, Pakistan: a
spatio-temporal view from Pothohar region-
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Abstract: The implications of climate change on water resources are of major concerns worldwide. Arid regions of the world need proper management for the water resources as climatic changes are bringing severe problems for their sustainability. Pothohar area of Pakistan is the most essential in this regard. A data set of 30 years of temperature, precipitation, and river discharge across the Pothohar Plateau were obtained from Pakistan Meteorological Department and Water and Power Development Authority, respectively. Hydro-meteorological data were subjected to a series of statistical methods for detecting trend and abrupt point changes. A rising trend in mean annual temperatures were noticed in all stations with most significant change in Jhelum and Attock stations (p < 0.05) during the period of 30 years while precipitation trends were found irregular, representing both scenarios of flash floods and droughts with non-significant change (p > 0.05). In addition, 2000 and 2001 are drought years in 30 years of time series, and the driest years were seen from 1999 to 2002. The discharge of River Haro and Soan were found downward significantly (p > 0.05), posing a threatening challenge to the future of water resources in this area. The correlation coefficient test revealed a substantial relationship between mean annual precipitation and river discharge, although the linear regression model demonstrated a diminishing trend with mean annual precipitation. Based on the analysis, it is concluded that modern techniques of irrigation and agriculture should be adopted to protect the future of the Pothohar area from climate change related extreme situations.
PubDate: 2023-05-09
- Multifractal detrended fluctuation analysis of particulate matter and
atmospheric variables at different time scales-
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Abstract: Anthropogenic and natural aerosol emissions poses a threat to human and animal health. Particulate matter has a complex relationship with atmospheric parameters. In this study, the multifractal detrended fluctuation analysis was used to investigate complexity in particulate matter and atmospheric parameters at five small time steps (6, 8, 10, 12, and 15 min) at a tropical location. The study was carried out at annual and monthly scale. Multifractal strengths in the range \(0.21-0.32\) , \(0.16-0.28\) , \(0.15-0.26\) , \(0.40-0.68\) , \(0.41-0.71\) , and \(0.12-0.23\) were obtained for PM1, PM2.5, PM10, temperature, humidity, and pressure respectively at the annual scale. At all time steps, multifractality of particulate matter was observed to decrease with increasing particle size. Multifractality in atmospheric parameters were found to reduce with increasing time steps. The monthly analysis suggests the influence of seasonal transitions on multifractality of particulate matter.
PubDate: 2023-05-08
- Predictive skill of extended range forecast of 2020–21 winter
precipitation over North India-
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Abstract: Winter precipitation occurs over North India due to the passage of a synoptic system originating from the Mediterranean known as western disturbances (WDs). Heavy rainfall, cold waves and fog are associated with WDs. Snowfall during winter over high-altitude regions of the Himalayas is vital for maintaining glaciers and Himalayan rivers, thus acting as a lifeline for billions of people living on the planes. Any predictive information about rainfall well in advance helps farmers fight drought situations, and forecasts of extreme events help save lives and property. In the present study, the multi-model ensemble based extended range forecast of winter rainfall over North India during the 2020–21 winter season is analyzed using the outputs of the National Centre for Environmental Prediction Climate Forecast System version 2 coupled model. The real-time forecast during the 2020–21 winter and hindcast during the 2003–2019 period are analyzed in this study. The study evaluates the deterministic and probabilistic skill of the extended range prediction system (EPS) in forecasting winter rainfall over North India on a weekly lead time scale and confirms the accuracy and usefulness of EPS from an operational point of view. EPS is skilful in predicting winter rainfall up to three weeks lead time in advance with low bias and low RMSE noted during the hindcast period. Positive anomaly correlation coefficients are observed in all lead time forecasts. Negative departure in rainfall during the January–February months is adequately captured in week 1, week 2 and week 3 forecasts. Probabilistic forecasts are determined using the ROC curve. Potential predictability of EPS is calculated using signal-to-noise ratio for all lead time forecasts.
PubDate: 2023-04-13
- Influence of coastal land–water–atmosphere interactions on tropical
cyclone intensity over the Bay of Bengal-
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Abstract: Jawad, an anomalous post-monsoon tropical cyclone (TC) that originated over the Bay of Bengal (BoB), renewed the challenges encountered in forecasting TCs by operational agencies, as the TC behaved contrarily in terms of predicted track and intensity. The novelty of this study is, for the first time, the impacts of the regional coastal land and ocean processes along with large-scale features are comprehensively examined that are regulated by the TC characteristics with thrust on its track and intensity. A total of four experiments, i.e., two Land Use Land Cover (LULC) datasets, viz., (1) United States Geological Survey (USGS), and (2) Indian Space Research Organization (ISRO) Advanced Wide Field Sensor (AWiFS) and two sea surface temperature (SST) datasets (i.e., INCOIS and default GFS) are tested to investigate the coastal processes using the Weather Research and Forecasting (WRF) model at a horizontal resolution of 3 km. The simulations are carried out with a lead time up to 96 h. Results suggested that ISRO LULC along with default SST experiment named as ISR (INCOIS SST and ISRO LULC named as INS) has the highest (lowest) forecast skills, i.e., track, intensity and precipitation. The vertical structures of specific humidity and the location of the updraft in ISRO LULC are associated with an accurate representation of latent heat flux (LHF) near the coast, enabling better intensity estimates of the cyclone. On the contrary, the overestimation of LHF led to the overestimation of intensity in INS. The results also highlighted that the land–atmospheric coupling index and storm energetics are better represented by ISR to support the realistic modulation of the intensification and associated convective processes. Interestingly, it is also noted that the effect of LULC on the energy exchanges between the surface and lower atmosphere in the coastal region is overridden by the effect of SST leading to poor results for INC (INCOIS SST and USGS LULC); therefore, choice of appropriate combination of LULC and SST is equally important for better forecast skills. This study demonstrates that an optimal combination of region-specific LULC and SST data is essential for accurate cyclone intensity prediction, particularly near the coastal region.
PubDate: 2023-04-08
- Features and sources of aerosol properties over the western Pacific Ocean
based on shipborne measurements-
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Abstract: In the Western Pacific, the limited in situ observations of aerosol optical depth (AOD) show substantial north–south differences in its spectral distribution, magnitude, seasonal fluctuation, and Angstrom exponent. Two sets of observation data collected in spring 2017 and summer 2019 are used to investigate aerosol size distribution and its sources through the GRASP (Generalized Retrieval of Aerosol and Surface Properties) inversion method and HYSPLIT (HYbrid Single-Particle Lagrange Integrated Trajectory) particle trajectories model. The retrieved aerosol size distribution (normalized by aerosol volume concentration) is homogeneous over the western Pacific Ocean. The aerosol volume concentration (Cv,c) in the coarse mode is substantially higher than that in the fine mode (Cv,f) in this region, indicating that coarse particles predominate. The northernmost section has the highest Cv,f with an average value of 0.04, which is 4.5 times that of the other sections except the sites observed in 2019, because of the Long-Range Transport (LRT) of dust from the Gobi and Mongolian Plateau. The equatorial section has the highest Cv,c with an average value of 0.22 for the coarse mode, which is 1.5 ~ 3 times higher than that of the other section. Its single scattering albedo (SSA) is the smallest in all sections (SSA(440) = 0.95). Analysis displays that the section is affected by elevated-smoke and polluted-continental/smoke types due to the biomass burning around Papua New Guinea. In addition, an AOD(500) with a value of 0.048, which is lower than the traditional oceanic AOD baseline, is obtained in summer 2019. In comparison to it, the projected net shortwave and longwave radiative effect of spring observed LRT high concentration PM10 plume (AOD(550) = 0.09) from Southeast Asia at the sea surface are − 3.1 W m−2 and − 1.4 W m−2 under clear sky conditions, resulting in a net radiative effect of − 1.7 W m−2. As the cold surge frequency increases due to the warming Arctic, more LRT events may be expected as a result of climate change.
PubDate: 2023-04-07
- Impact of dropsonde data on two tropical cyclone forecasts in the South
China Sea-
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Abstract: By using the dropsonde data collected by the Hong Kong Observatory over the northern South China Sea in 2020 and the South China Regional Fine Forecast Model, the impact of these dropsonde data on the forecast of two tropical cyclones (Higos, and Nangka) was assessed. The results indicated the following: (1) The effect of the data assimilation on the wind and humidity fields lasted up to 24 h, whereas the assimilation did not exert a noticeable impact on the temperature forecast. (2) The mean track forecast errors of the two tropical cyclones, Higos and Nangka, were reduced by 34% and 24%, respectively, after the assimilation of the dropsonde data, but no fundamental improvement was made in intensity forecasts, such as in minimum sea level pressure. (3) The sensitivity tests of the two tropical cyclones showed that the assimilation of the observed wind field had the greatest impact on the cyclone track forecast. Sensitivity tests revealed that the assimilation of data altered the cyclone’s steering flow, thereby changing the movement path and improving the forecast performance. Assimilation of the observed humidity alone has no substantial impact on the track forecasts.
PubDate: 2023-04-06
- Study of atmospheric dispersion of radioactive effluents under inversion
condition at coastal station Kalpakkam for radiological impact-
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Abstract: This study investigates the impact of inversion layers on the dose due to air-born radioactive effluents at tropical coastal site Kalpakkam. Observations from a meteorological tower, GPS Sonde and SODAR are used to identify the presence of inversion conditions. A high resolution mesoscale model WRF is used to simulate the boundary layer meteorological fields. Sensitivity tests with two PBL schemes indicated that the non-local scheme YSU better produced the observed inversion characteristics. Both simulations and observations indicated that inversion layers are marked with strongly stable atmosphere characterized by steep positive temperature gradients and high values of bulk Richardson number. Simulations using FLEXPART dispersion model for hypothetical tracer release on typical days indicated that inversion condition leads to roughly 3 times higher ground level concentration compared to daytime unstable conditions due to confining the plume to a shallow surface layer. FLEXPART simulations using WRF-YSU meteorological data produced roughly 2 to 3 times higher concentrations during inversion condition and roughly 0.5 to 0.7 times lower concentration during daytime unstable condition compared to MYNN. Simulations conducted with FLEXPART for routine Ar-41 releases from an operational reactor at the coastal site suggest that the plume gamma dose rate during inversion condition is almost 2 to 3 times more compared to daytime convective unstable atmospheric condition. Analysis of simulated particle positions suggested that inversion layers trap the radioactive effluents, thereby lead to relatively higher dose rates compared to unstable daytime conditions. The study shows that inversion layers cause unfavourable conditions for dispersion of radioactive effluents and increases the radiological impact.
PubDate: 2023-04-04
- Climatic characteristics of mesoscale convective systems in the warm
season in North China-
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Abstract: In this study, a total of 339 mesoscale convective systems (MCSs) are obtained in North China using the temperature of brightness blackbody (TBB) data from the FY-2E in the warm season from 2010 to 2018. The number of meso-α-scale convective systems (MαCSs) is much more than that of meso-β-scale convective systems (MβCSs). The number of mesoscale elongated convective systems (MECSs) is more than that of mesoscale circular convective systems (MCCSs). Most MCSs occur in July and August, which have the widest influence range, the longest duration, and the strongest convection. The MαCS develops slowly and weakens rapidly. The diurnal variation of MαCSs presents a bimodal distribution, most of MαCSs form in the afternoon, while some of MαCSs form in the evening. The MCSs activities in the warm season of North China are concentrated in two belts, namely, the east–west-oriented belt along Henan Province, Shandong Province and the Yellow Sea, and the south–north-oriented belt along central-western Shandong, Tianjin City, the west of Bohai Sea and the northeast of Hebei Province. MCSs mainly move eastward, and only some MECSs move southwestward and northwestward. The easterly and northerly moving MCSs are mainly affected by the steering flow, while the southerly moving MCSs are mainly affected by storm propagation. The MCSs of North China mainly form in the high temperature, high humidity and high energy area, with favorable dynamic conditions, such as middle-level trough or vortex, low-level shear line, surface inverted trough or surface convergence line, and the terrain. Meanwhile, the MCS pregnant environment is often accompanied by low-level jet and relatively strong vertical wind shear.
PubDate: 2023-03-16
DOI: 10.1007/s00703-023-00958-1
- A diagnostic study of heavy rainfall events in upper Ganga and Sharda
river basins, India-
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Abstract: Upper Ganga (UG) and Sharda are two river basins in Uttarakhand, India that are situated in the western Himalayan region. Previous studies revealed that these basins are prone to high seasonal rainfall (more than 100 cm) and substantial interannual variations during the southwest monsoon season. However, synoptic situations causing heavy rainfall events in the basins are not properly understood. The present study attempts to understand the synoptic situations causing heavy rainfall events in the basins using synoptic analogue and rainfall data from India Meteorological Department, followed by a diagnostic assessment using ERA5 reanalysis data. The synoptic systems associated with heavy rainfall events in the basins are found to be different. Heavy rainfall events in UG are triggered by the movement of mid-latitude systems (trough in westerlies) towards north India which provide convergence at middle and upper tropospheric levels. These systems strengthen when they are supported by the northward progression of the monsoon trough (especially the western end of the monsoon trough) and embedded cyclonic circulations. We found that heavy rainfall events in UG are associated with the development of a cyclonic circulation extending up to the mid-troposphere/low-pressure system in the northwest Bay of Bengal. The mid-tropospheric divergence over this cyclonic circulation system feeds moisture to the convergence due to the southward extended trough in the mid-latitude westerlies and caters to the formation of heavy rainfall events in the basin. Heavy rainfall events in Sharda are associated with the movement of low-pressure systems from the Bay of Bengal towards the region, which provides anomalous convergence in the lower levels. It is supported by a trough in the mid-latitude westerlies in the mid and upper tropospheric levels, which increases the convergence at lower and mid-tropospheric levels and leads to heavy rainfall events in the basin. This study reveals the tropical-midlatitude interaction and its role in the heavy rainfall events over the western Himalayan region.
PubDate: 2023-03-15
DOI: 10.1007/s00703-023-00954-5
- Exploring the asymmetry and rate of SAT warming over the global land area
under the 1.5 °C and 2 °C climate change targets-
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Abstract: The Paris Agreement establishes targets for the increase in global mean temperature of 1.5 °C and 2 °C, relative to pre-industrial levels. Recent studies suggest that the climate change impacts of these two goals are markedly different, and the additional 0.5 °C increase in the global mean surface air temperature (SAT) may lead to drastic, non-linear increases in the extreme and average temperatures of most regions. In this study, we use model results from the Coupled Model Intercomparison Project 5 (CMIP5) to illustrate the asymmetric nature of the warming trends that will result over the global land area under these two climate change targets. The results show that the SAT increase reaches 1.5 °C by 2040 (2040 ± 6), considering RCP2.6 to RCP8.5, whereas the SAT increase reaches 2.0 °C by 2060 (2060 ± 12), considering RCP4.5 to RCP8.5. The SAT increase over land is meridionally and zonally asymmetric, especially in the Northern Hemisphere. What’s global warming and rising concentrations of emissions will exacerbate the asymmetric warming from north to south especially over land. In addition to the longitudinal changes, the magnitude of the SAT increase at higher latitudes is significantly greater than that of comparable areas at middle to low latitudes. Additionally, the time of the SAT increase over the high-latitude land areas occurs much earlier than elsewhere. In addition, the difference in the timing of this onset in the longitudinal direction is substantial, but the difference in the zonal direction is small. Furthermore, the SAT increase over most of the global land area reaches 1.5 °C before the middle of twenty-first century and reaches 2.0 °C before 2070. In addition, over 20% of the global land area, the SAT increase reaches 1.5 °C before 2006, whereas almost none of the land area exhibits a change of 2.0 °C before 2006.
PubDate: 2023-03-14
DOI: 10.1007/s00703-023-00957-2
- Application on using the infinite medium vector Green’s function for
polarized radiation in a Rayleigh-scattering atmosphere-
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Abstract: The radiative transfer equation has wide application fields, such as atmospheric optics, oceanography, biomedical physics, and optical tomography. This paper presents the investigation of the vector radiative transfer equation for polarized radiation transport in optically semi-infinite, homogeneous, Rayleigh-scattering atmosphere with no interior source using an analytical approximation. The spatial attenuation coefficient, the outward-to-inward flux ratio, and the mean cosine, which were defined in terms of the total intensity component, I, were calculated for Rayleigh-scattering case using the infinite medium Green’s function. The behaviors of these parameters were obtained as a function of the optical depth.
PubDate: 2023-03-10
DOI: 10.1007/s00703-023-00956-3
- Surface atmospheric electric field variability on the Qinghai-Tibet
Plateau-
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Abstract: The variability in the atmospheric electric field needs to be understood before considering the properties of the atmospheric electrostatic distribution on the Tibetan Plateau. The relationship between each meteorological parameter and the atmospheric electric field should be carefully considered. In this article, atmospheric electric field observations and their effects from weather conditions at Gar Station (80.13°E, 32.52°N, altitude 4259 m) for the period from November 2021 to October 2022 are presented. After defining strict and reliable criteria for fair weather, the authors show the diurnal variation curve of the average fair weather atmospheric electric field, which has “double peaks and double valleys”. How various meteorological conditions affect variability in the atmospheric electric field and comparisons between the Gar curve and “Carnegie curves” are also revealed.
PubDate: 2023-02-22
DOI: 10.1007/s00703-023-00955-4
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