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Relative humidity (RH), an important climatic element influencing tree growth, is also crucial in assessing the General Circulation Models (GCMs) on global warming. However, in the absence of a relatively long record of RH in the Himalayan region, precise modelling of the climate change related processes and their impacts on this region are not well established. Here we present a new RH reconstruction for the pre-monsoon months (February–May) starting from 1800 C.E. using the tree-ring width data of subtropical Pinus roxburghii (chir-pine) from Pithoragarh, Western Himalaya, India. We found significant positive correlation between tree growth and pre-monsoon RH (n = 67, r = +0.569, p

This study reports for the first time a comprehensive analysis of nitrogenous and carbonaceous aerosols in simultaneously collected PM2.5 and TSP during pre-monsoon (March–May 2018) from a highly polluted urban Kathmandu Valley (KV) of the Himalayan foothills. The mean mass concentration of PM2.5 (129.8 µg/m3) was only ~25% of TSP mass (558.7 µg/ m3) indicating the dominance of coarser mode aerosols. However, the mean concentration as well as fractional contributions of water-soluble total nitrogen (WSTN) and carbonaceous species reveal their predominance in find-mode aerosols. The mean mass concentration of WSTN was 17.43±4.70 µg/m3 (14%) in PM2.5 and 24.64±8.07 µg/m3 (5%) in TSP. Moreover, the fractional contribution of total carbonaceous aerosols (TCA) is much higher in PM2.5 (~34%) than that in TSP (~20%). The relatively low OC/EC ratio in PM2.5 (3.03 ± 1.47) and TSP (4.64 ± 1.73) suggests fossil fuel combustion as the major sources of carbonaceous aerosols with contributions from secondary organic aerosols. Five-day air mass back trajectories simulated with the HYSPLIT model, together with MODIS fire counts indicate the influence of local emissions as well as transported pollutants from the Indo-Gangetic Plain region to the south of the Himalayan foothills. Principal component analysis (PCA) also suggests a mixed contribution from other local anthropogenic, biomass burning, and crustal sources. Our results highlight that it is necessary to control local emissions as well as regional transport while designing mitigation measures to reduce the KV's air pollution.

The first experiment studying the effect of irrigation on pre-monsoon rainfall in India using a high-resolution convection-permitting model has been carried out. This study includes both short (3-day) experiments and month-long free-running simulations, enabling investigation of the effect of irrigation on mesoscale circulations and associated rainfall. In the pre-monsoon, it is found that irrigation increases rainfall in our simulations. Intriguingly, the rainfall increase found in the high-resolution model mostly occurs on the mountains near the irrigation rather than over the irrigated region itself. This is because our applied irrigation is in low-lying regions, and so it enhances the mountain-valley flows leading to enhancement of diurnally driven orographic rainfall. Because Ganges basin irrigation occurs near mountains which already have some of the highest rainfall rates in the world, and which are subject to flash flooding and landslides, this has significant implications for hazards in mountainous regions during the pre-monsoon and early monsoon period.

This study has been carried out to find the groundwater quality of Burdwan district of West Bengal during pre-monsoon and post-monsoon. For this, the data of physicochemical parameters have been collected from Central Pollution Control Board (CPCB) website for the pre-monsoon and post-monsoon season for the year 2017. It is found that during the post-monsoon season, the water quality of all the stations falls in the category of excellent, and during the pre-monsoon season, the water quality of most of the stations is good.

Monsoon rainfall is the dominant factor that determines the success or failure of agriculture in general. Gangetic West Bengal is not any exception. Monsoon rainfall has immense importance for growing kharif rice in this region. Whereas pre-monsoon rainfall helps farmers for proper crop planning like choosing variety etc. So assessing a long (1901-2005) and short (1961-2005 and 1991-2005) period rainfall data, its comparison with different models and construction of future scenario have utmost importance. For this purpose, rainfall data from nine selected station of India Meteorological Department were collected and subjected to trend analysis. Model outputs were compared with the observed station data. Results showed an overall negative trend of pre-monsoon rainfall during 1901-2005. However, increasing trend in monsoon rainfall was noticed during the same period. In future scenario, monsoon rainfall indicates a nominal increase (~6%) whereas pre-monsoon rainfall increases in moderate amount (~11%). So, from the study it may be said that in near future farmers and crop planner should give more importance in pre-monsoon rainfall for better crop planning and other stake holder activities.

In this paper, pre-monsoon (March – May) Cloud to Ground (CG) lightning activity over 6 mega cities (New Delhi, Kolkata, Mumbai, Chennai, Bengaluru and Hyderabad) in India is analysed with concentrations of four surface pollutants namely particulate matters (PM2.5, PM10), Sulphur dioxide (SO2) and Ozone for a period of 2018 to 2021 that includes the lockdown year 2020. Pollution greatly reduced with an enhancement of air quality in this year. Lightning data for the analysis is derived from the ground based lightning Network -Earth Networks Global Lightning Network (ENGLN). Among the mega cities, Kolkata faces most lightning whereas Mumbai receives the least. CG lightning flash counts significantly decrease in 2020 for Kolkata, Bengaluru, New Delhi and increase for Chennai, Hyderabad and Mumbai though the increase for the last two cities are very insignificant. This increase may be due to greater impact of meteorological factors on lightning than the pollutant concentrations. The lightning activity averaged over all the mega cities follows the trend of pollutant concentrations and average CG lightning flash counts go to minimum in the COVID-19 lockdown year 2020. Analysis also reveals that average seasonal CG lightning flash counts, average positive CG lightning flash counts and maximum peak CG currents show positive correlations with the concentration of all the four pollutants. The overall study shows that control of pollution may reduce the lightning activity in some lightning prone urban areas.

This rainwater chemistry study was carried out during monsoon and pre-monsoon seasons in 2018. The rainwater samples were collected in the residential area of Sitapuri which is situated the southwest zone of city Delhi. The rainwater samples were collected with the help of the funnel and bottle assembly on event basis. To refrain any contamination from the ground, the assembly was mounted at 5m above the ground level on a terrace. The assembly was always installed on the onset of rain and retrieved soon after the rain stopped. The collected samples were filtered. The samples were analyzed for Mercury (Hg0), Total Nitrogen (TN) and Dissolved Organic Carbon (DOC). The Hg(o) determination was done using Differential Pulse Anodic Stripping Voltammetry through standard addition methods and DOC species and TN species were determined using DOC/TN analyzer (Shimadzu model LCPH/CPN). The average concentration of Hg0 was recorded as 54.9 μg/l, while that of DOC and TN as 160.2 mg/l and 12.6 mg/l respectively. The study indicated that Hg0 and DOC were not contributed by common emission sources. Also, the study indicated that pre-monsoon air was more contaminated with Hg (0), TN and DOC as compared to the monsoon season.

The aim of the study is to understand trend or non-linearity along with a chaotic behaviour, if any, of Eastern and North Eastern sub-divisional rainfall, namely Orissa, Gangetic West Bengal, Sub Himalayan West Bengal, Assam and Meghalaya and also Nagaland, Manipur, Mizoram and Tripura based on rainfall data of 143 years (1871-2013). The analysis is performed for examining behaviour of rainfall in each of the seasons, namely, Pre monsoon, South West monsoon, North East monsoon and also Annual rainfall extracted from the monthly data. For that purpose, a trend analysis with Hurst Exponent and non-linearity analysis with Lyapunov Exponent are employed. The analysis revealed that rainfall of Orissa is persistent for all the seasons whilst the rainfall is persistent in Gangetic West Bengal in Pre monsoon and North East monsoon and Assam and Meghalaya along with Nagaland, Manipur, Mizoram and Tripura exhibit persistent behaviour in South West Monsoon and annually. Sub Himalayan West Bengal exhibit persistence in annual rainfall only. Chaotic tendency in low magnitude is located in many cases whilst non-chaotic situation has occurred when the persistence is found, mainly in pre-monsoon season. Moreover, the analysis of Hurst and Lyapunov Exponent revealed to identify two groups of sub-divisions with exactly similar region of every respect. Those two groups contain (i) sub-divisions Orissa and Assam and Meghalaya and also (ii) sub-divisions Sub Himalayan West Bengal and Nagaland, Mizoram, Manipur and Tripura although those are at distances of hundreds of kilometers away. The behaviour of those subdivisions in a group has similar behaviour in all respects.

During the pre-monsoon season, biomass burning (BB) activities are intensive in southern Asia. Facilitated by westerly circulation, those BB plumes can be transported to the Tibetan Plateau (TP). Black carbon (BC), the main aerosol species in BB emissions, is an important climate warming agent, and its absorbing property strongly depends on its size distribution and mixing state. To elucidate the influence of those transported BB plumes on the TP, a field campaign was conducted on the southeast edge of the TP during the pre-monsoon season. It was found that the transported BB plumes substantially increased the number concentration of the atmospheric BC particles by a factor of 13 and greatly elevated the number fraction of thickly coated BC from 52 % up to 91 %. Those transported BC particles had slightly larger core size and much thicker coatings than the background BC particles. However, the coating mass was not evenly distributed on BC particles with different sizes. The smaller BC cores were found to have larger shell / core ratios than the larger cores. Besides, the transported BB plumes strongly affected the vertical variation in the BC's abundance and mixing state, resulting in a higher concentration, larger number fraction, and higher aging degree of BC particles in the upper atmosphere. Resulting from both increase in BC loading and aging degree, the transported BB plumes eventually enhanced the total light absorption by a factor of 15, of which 21 % was contributed by the BC aging, and 79 % was contributed from the increase in BC mass. Particularly, the light absorption enhancement induced by the aging process during long-range transport has far exceeded the background aerosol light absorption, which implicates a significant influence of BC aging on climate warming over the TP region.

Purpose of the study: The purpose of this study is to make sure that the Bird valley’s quarry water is suitable for drinking purposes or not and to monitor the seasonal variations in the physico-chemical parameters of this quarry water. Methodology: Water samples from the quarry were collected in clean and sterilized polyethylene bottles. Water samples were collected from different points and mixed together to get an integrated sample. Some of the selected physico-chemical parameters of the quarry water have been analyzed. Results were compared with standard limits of IS: 10500-2012. All the parameters were analyzed in the laboratory by using standard methods and techniques. Main Findings: As per the obtained results this quarry water contains a very large number of Coliforms detected in the months of September and December and in June month Coliform count was 33 CFU/ml. This overall result for coliform is making this quarry water unfit for domestic purposes. Applications of this study: This study helps us to understand the current condition of this quarry water and also enables us to know whether the quarry water is fit for drinking purposes. It also enables us to know whether this quarry water can be used for domestic purposes after the treatment. Novelty/Originality of this study: Bird valley’s quarry water has not been analyzed from this point of view till date. This study will help us to understand the present condition of the water.

A “hot blob”, distinct hot region, is identified over Vidarbha in the south-central parts of the Indian subcontinent during the pre-monsoon season from the analysis of gridded surface air maximum temperature data from India Meteorological Department for the period 1951–2019. Spatial distribution and frequencies of temperatures > 40 °C and > 42 °C establish the hot blob over Vidarbha region. A similar analysis of simulated maximum temperatures from the NEX-GDDP substantiates the revelation of the “hot blob” over Vidarbha. Further, analysis of the wind circulation at 850 hPa over South Asia region indicates that the “COL” region between the two seasonal high-pressure systems over the Indian Ocean seas, Bay of Bengal and Arabian Sea promotes accumulation of heat over Vidarbha. Further, horizontal temperature convergence complimented by strong local heating of the black soil aids and abets the sustenance of the “hot blob”. This “hot blob” region is observed to be hotter as well as having higher frequencies of hot days than the north-west desert Rajasthan region and assumes importance as its modulation causes heatwaves over the south-east coastal regions. This study establishes the presence of the hottest region over Vidarbha in south-central parts, paradoxically hotter than the desert north-west region of India.

India is frequently exposed to convective systems (CS) during the hot period of pre-monsoon season. Huge thunderstorms are more often over India in the recent years. To analyze these systems, the stability parameters considered as good precursors for understanding the physics of the convective systems in prior to their occurrence. The present study is concerned about the analysis of stability parameters such as K Index (KI), Lifted Index (LI), Total Totals Index (TTI), Humidity Index (HI), Convective available potential energy (CAPE), Convective Inhibition (CIN), Lifting Condensation Level (LCL) and Level of free Convection (LFC) associated with severe convective systems over India and Srilanka during April, 2015. First, INSAT-3D satellite based brightness temperature (BT) product was used for analyzing the initial, mature and dissipation stages of the convective system at every 30 min interval. The data products from MODIS Terra satellite, MODIS Aqua satellite, Era-Interim ECMWF reanalysis satellite data and IASI satellite were used for understanding the thermodynamics related to the occurrence of these convective systems. The results of stability parameters that were derived from MODIS Terra and Aqua satellite’s data products indicated the favorable threshold values for the occurrence of convective systems. Results from Era-Interim ECMWF reanalysis satellite data also helps us to understand the dynamics involved behind the convective system. The results from IASI satellite also helped us to understand the severity of convective systems during cloudy situations. The results of this study impulse the need of satellites for analyzing the convective systems prior to their occurrence.

The present study analyses thermodynamic indices variation over three sites of eastern Indian region: Bhubaneswar, Kolkata and Ranchi, associated with pre-monsoon thunderstorms for 20-year period (1987–2006) for Bhubaneswar and Kolkata and 15 years (1996–2010) for Ranchi. All three sites are showing a rise in humidity over the period, unveiling the climate change over the region. We evaluated the threshold values of various thermodynamic indices for periods of 5-year intervals at each site based on skill score analysis. The indices associated with potential, convective, latent instability and moisture are showing varying threshold values over all the sites, and some of the indices are showing a definite increase/decrease in these threshold values. All three sites are showing a decrease in thunderstorm frequency over the study period. The work identifies the thermodynamic indices, which tend to capture the global warming impact in the threshold values by either showing an increase or decrease with the time at each site. The results advocate that for a long-term analysis of thermodynamic indices, the threshold values may change from one period to another.

The 21 year moving averages of all-India pre-monsoon rainfall (PMR) shows epochal changes. The interesting fact is the presence of an increasing trend during 1970–2015. This change is closely associated with global warming. The tendencies of rainfall during this period are evaluated over India using gridded rainfall data. The differences in the mean rainfall between the global warming period (1970–2015) and the pre-global warming period (1901–1969) are evaluated. It seems that the major area of India is having positive differences and positive tendencies. In this study, the active and weak pre-monsoons are discriminated during 1979–2015. The composite mean differences in the rainfall of active and weak pre-monsoons have been evaluated using the daily gridded rainfall data. And also, the composite mean frequencies and their differences of different rainfall events i.e., wet, dry, very light rain, light rain, moderate rain, rather heavy, heavy rain, very heavy rain and extremely heavy rain days are analyzed. The factors responsible for the spatial and temporal evolution of the rainfall composite patterns are elucidated with the help of changes in the thermal, moisture and circulation patterns over India and neighborhood. The scrutiny reveals that the rainfall of the active/weak pre-monsoons in the recent 37 years is primarily associated with (1) the strengthened/weakened low level circulation, (2) increase/decrease in the convective available potential energy (CAPE), sea surface temperature (SST), vertical integrated moisture flux convergence (VIMFC) and relative humidity (RH) and (3) decrease/increase in the outgoing long-wave radiation (OLR). Furthermore, an attempt is made to understand the concurrent/forecast relationships between PMR and the Atlantic Multi-decadal Oscillation Index (AMO), Effective Strength Index (ESI), Southern Oscillation Index (SOI) and Sunspot number of pre-monsoon/winter season.

The assessment of the human-induced climate change on a global level can be carried out only after the study of local and regional climate change patterns. This study was an attempt to establish a link between regional climate and the surface parameters. The study was carried out for Ranchi, India to assess the changes in climatic pattern over the years (1901-2016) and applied Mann-Kendall Trend analysis test. The pre-monsoon period was chosen due to high intensity and number of thunderstorms taking place in the study area. Maximum temperature (Tmax), minimum temperature (Tmin), rainfall (P) &diurnal temperature range (DTR) for the months (March, April & May) were studied, and a significant negative trend in Tmax and DTR was observed. Autoregressive Integrated Moving Average (ARIMA) model was applied to fit the datasets and predict 5 values for the meteorological parameters, and the model depicted positive temperature trends and negative rainfall and DTR trends in the future. Land surface process parameters such as sensible heat flux, momentum flux, frictional velocity, shortwave radiation, longwave radiation, and net radiation for Ranchi were also fit into the ARIMA model, and the fitness of the model and predictions were determined.

This paper presents the preliminary results of observation of total lightning characteristics of pre-monsoon thunderstorms of 2018 over Gangetic West Bengal around Kolkata. Mainly, the analysis results of total lightning associated with pre-monsoon moderate and severe thunderstorm events, locally known as Kalbaishakhi or Nor’wester, are presented. The total lightning data include both in-cloud and cloud-to-ground lightning flashes and are obtained from the Earth Networks Total Lightning Network. Most of the events were multi-cellular in nature as inferred from lightning data. The total lightning count over an area of 10 km radius around the wind sensors, increased rapidly about $$\sim $$ 10–40 min before the onset of high wind on the surface. Primarily, total lightning count $$\ge 30$$ per minute was found to be associated with the Nor’westers which produced maximum surface wind speed above 50 km/h.

The potential of single date fully polarimetric SAR data was brought out in discriminating different land covers at level 3 (LULC classification system NRSC) by deriving various polarimetri...

The Ganges-Brahmaputra-Meghna (GBM) river basin is the world’s third largest. Literature show that changes in precipitation have a significant impact on climate, agriculture, and the environment in the GBM. Two satellite-based precipitation products, Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Climate Data Record (PERSIANN-CDR) and Multi-Source Weighted-Ensemble Precipitation (MSWEP), were used to analyze and compare precipitation trends over the GBM as a whole and within 34 pre-defined hydrological sub-basins separately for the period 1983–2019. A non-parametric Modified Mann-Kendall test was applied to determine significant trends in monsoon (June–September) and pre-monsoon (March–May) precipitation. The results show an inconsistency between the two precipitation products. Namely, the MSWEP pre-monsoon precipitation trend has significantly increased (Z-value = 2.236, p = 0.025), and the PERSIANN-CDR monsoon precipitation trend has significantly decreased (Z-value = −33.071, p &lt, 0.000). However, both products strongly indicate that precipitation has recently declined in the pre-monsoon and monsoon seasons in the eastern and southern regions of the GBM river basin, agreeing with several previous studies. Further work is needed to identify the reasons behind inconsistent decreasing and increasing precipitation trends in the GBM river basin.

The climate of Bangladesh is very likely to be influenced by global climate change. To quantify the influence on the climate of Bangladesh, Global Climate Models were downscaled statistically to produce future climate projections of maximum temperature during the pre-monsoon season (March–May) for the 21st century for Bangladesh. The future climate projections are generated based on three emission scenarios (RCP2.6, RCP4.5 and RCP8.5) provided by the fifth Coupled Model Intercomparison Project. The downscaling process is undertaken by relating the large-scale seasonal mean temperature, taken from the ERA5 reanalysis data set, to the leading principal components of the observed maximum temperature at stations under Bangladesh Meteorological Department in Bangladesh, and applying the relationship to the GCM ensemble. The in-situ temperature data has only recently been digitised, and this is the first time they have been used in statistical downscaling of local climate projections for Bangladesh. This analysis also provides an evaluation of the local data, and the local temperatures in Bangladesh show a close match with the ERA5 reanalysis. Compared to the reference period of 1981–2010, the projected maximum pre-monsoon temperature in Bangladesh indicate an increase by 0.7/0.7/0.7 ∘C in the near future (2021–2050) and 2.2/1.2/0.8 ∘C in the far future (2071–2100) assuming the RCP8.5/RCP4.5/RCP2.6 scenario, respectively.

Globally, the highest formation rate of super tropical cyclones (TCs) occurs over the Bay of Bengal (BoB) during the premonsoon transition period (PMT), but TC genesis has a low frequency here. TCs have occurred over the BoB in only 20 of the past 36 years of PMTs (1981–2016). This study investigates which environmental conditions modulate TC formation during the PMT over the BoB by conducting a quantitative analysis based on the genesis potential parameter, vorticity tendency equation, and specific humidity budget equation. The results show that there is a cyclonic anomaly in the TC genesis group compared to the non-TC genesis group, which is mainly due to the divergence term. A significant difference in vorticity contributes to TC formation over the BoB during the PMT. Furthermore, anomalous cyclonic flow enhances ascending motion, transporting moisture to the midlevel atmosphere. A change in specific humidity (SH) causes an increase in relative humidity, which contributes positively to TC formation. The vertical wind shear also makes a small positive contribution. In contrast to the previous three terms, the contribution from the instability term associated with 500- and 850-hPa air temperatures is negative and almost negligible. In addition, the synoptic-scale disturbance energy is more powerful in the TC genesis group than in the non-TC genesis group, which is favorable for TC breeding. Together, these conditions determine whether TCs are generated over the BoB during the PMT.

In the present study, the spatiotemporal structures of the northward-propagating intraseasonal oscillation (ISO) over the South China Sea (SCS) in the premonsoon period are analyzed by using the TropFlux air–sea flux and the JRA-55 reanalysis datasets. It is found that the SCS ISO is significant in the premonsoon season with a strong component of the northward propagation and that the mean state is different from that of summertime. Moreover, there are similar structures to those of a boreal summer ISO event except for the perturbation vorticity with no obvious phase leading. An internal atmospheric dynamics mechanism is proposed to understand the cause of the northward propagation of the ISO during the premonsoon period based on the spatial and temporal structures of the ISOs. The key process associated with this mechanism is the barotropic vorticity advection by the mean barotropic southerly winds, and the main barotropic vorticity around the convection center can be induced by the vertical advection of the mean vorticity. Low-level moisture convergence caused by anomalous flow is a supplementary mechanism to drive the ISOs northward during the premonsoon period, particularly over the northern SCS. In this mechanism, the SST-induced wind anomalies play a more important role than the convection-induced wind anomalies. The summer monsoon circulation has not built up during the premonsoon period, and thus the vertical wind shear effect and the barotropic vorticity effect associated with the meridional advection of baroclinic vorticity are not essential to cause the northward propagation of the ISOs over the SCS.

Waste management is an international sensation, rising population, industrialization and urbanization are accountable to produce a tremendous amount of waste. Today's daily waste generation rate is about 760,000 tons. By 2025, this rate will be increased to about 1.8 million tons per day. These approximations are conservative the real values are probably double of this amount. 1 The estimated municipal solid waste generation by 8 Municipal Corporations and 9 Municipal Councils in Mumbai Metropolitan Region MMR cumulatively generate more than 10,000 metric tons of solid waste per day. Due to growth in population, industrialization and urbanization, the generation of solid waste has increased frighteningly. There is a high need for systematic management of municipal solid waste and for that understanding of characteristics play a vital role in it. In these research paper characteristics of Deonar dumping, yard has been studied on pre monsoon and post monsoon bases and encounter that, it contained some amount of organic and recyclable part, which if managed well, will reduce the load on dumping yard considerably. Dabhi Jagrutiben | Abhay Shelar "Analytical Study of Municipal Solid Waste Characteristics at Deonar Dumping Yard in Mumbai Region, Maharashtra, India" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-3 , April 2019, URL: https://www.ijtsrd.com/papers/ijtsrd23333.pdf

A field-cum-laboratory study was conducted to ascertain the quality of sub-surface water of North-Eastern Haryana, India. Thirty sub-surface-water samples were collected from the region during April 2017 and were analysed for hydro-chemical elements, analytical parameters and heavy metals. Presence of cations was found to be satisfactory at 86.67% of the locations while 93.33% samples were found to be in the acceptable range for anions. The analytical parameters of pH, TDS, TA and TH were found to be satisfactory in 100%, 60%, 80% and 76.66% of the samples, respectively. Eight sampling sites of the study area showed undesirable limits of one or more of the hydro-chemical elements. Location 23 (Matedi Bus Stand) has been observed to be adversely affected by excess of Ca2+, SO42−, TDS, TA and TH and is declared to be falling in the ‘Red Zone’. Seven sites are identified to be suffering from one element and hence are categorised to be falling in the ‘Grey Zone’. The classification of samples indicated that most of the samples fall in ‘Ca2+-Mg2+-HCO3--Cl-' hydro-chemical facies . Gibbs plot represented that sub-surface water quality variation is possibly attributed by rock-water interactions in groundwater. The study is expected to help the planners and officials of local bodies to take suitable remedial measures towards provision of safe drinking water to the people.

This paper investigates the frequency of severe weather phenomena such as thunderstorm, hailstorm, thundersquall and cyclonic disturbances for some selected stations of Gangetic West Bengal for the prediction of all these devastating phenomena with the aid of Doppler weather radar products along with the critical consideration of their meteorological association. Attempts have been made to conclude some common features of the nor’westers in Gangetic West Bengal during pre-monsoon season. From the analysis, it may be stated that Doppler weather radar products of Regional Meteorological Centre Kolkata are the supreme means for the nowcasting of all severe weather phenomena in the range of 250 km around Kolkata, i.e. Gangetic West Bengal and its surroundings.

The present paper reports a comparative study among two neurocomputing models in the form of Multilayer Perceptron (MLP) models and non-linear regression for the prediction of surface ozone (O3) during pre-monsoon season over Gangetic West Bengal (GWB), India considering NOx, SO2, PM10 and temperature as predictors. Learning the MLPs through gradient descent (GD) with tanhyperbolic and sigmoid nonlinearities, we found that all the models under consideration have almost the same degrees of prediction efficiency for O3 over GWB during pre-monsoon season with the said predictors. However, the MLP model with tanhyperbolic activation function is found to produce a significantly higher correlation and Willmott's index of agreement between actual and predicted O3 than the other models. Finally, MLP with GD learning characterized by tanhyperbolic nonlinearity is identified to have significant efficiency in surface ozone prediction over the region as mentioned above.

This study was designed to deliver a better concurrence between model estimates and observations, of atmospheric aerosol species, and predict their spatial distribution as consistently as possible. A free running aerosol simulation ( freesimu ) in a general circulation model (GCM) was performed, and further the simulated aerosol optical depth (AOD) was constrained with the observed AOD. The present study was carried out during the pre-monsoon season and for the Tigerz experiment which was conducted at stations over the Indo-Gangetic plain (IGP) and the Himalayan foot-hills in northern India. Our formulation of the constrained aerosol simulation ( constrsimu ) was based upon an identification of the freesimu with the most consistent estimates of aerosol characteristic among the three freesimu . The three freesimu (differing in source of emissions and model horizontal resolution) were carried out with the general circulation model (GCM) of Laboratoire de Meteorologie Dynamique (LMD-ZT GCM). Black carbon (BC), organic carbon (OC), and sulfate-other water soluble (Sul-ows) estimated from constrsimu amounted to 70%–100% compared to that from freesimu being 20%–50% of their measured counterparts. Among the aerosol species, the pre-monsoon mean concentration of dust was considerably high over most part of the Indian subcontinent; the anthropogenic aerosol species were, however, specifically predominant over the IGP (mostly 8–12 μ g m −3 for Sul-ows, OC). The constrsimu estimated total submicron aerosol mass concentration revealed its alarmingly high value over the northern and north-western India (> 100 μ g m −3 and as high as 300 μ g m −3 ). While the high value of observed AOD was found being mainly due to dust (AOD due to dust greater than 0.3) over the northern–northwestern IGP, it was due to Sul-ows (AOD due to Sul-ows as high as 0.4) over the eastern IGP, eastern coastline, and the Bay of Bengal. Temporal trend of fine (FM) and coarse mode (CM) AOD from constrsimu estimates and that derived from Tigerz experiment were in phase with each other for most of the days and exhibited a strong positive correlation coefficient. Source of Tigerz aerosols was mainly due to a predominant influence of dust from Africa/west Asia followed by that from northwest India, and of anthropogenic emissions originating in the IGP. A 200% increase was inferred for potential black carbon emissions (using India emission inventory implemented in a GCM) to obtain a concurrence between observed and freesimu BC concentration.

Four years (2015-2018), Joss-Waldvogel disdrometer (JWD) data are utilized for the statistical analysis of Raindrop size distribution (RSD) of pre-monsoon and monsoon season over the Western Ghats. JWD Instrument installed at High Altitude Cloud Physics Laboratory (HACPL, 17.92°N, 73.66°E), Mahabaleshwar in the core of heavy rainfall region of Western Ghats. Variation in raindrop size distribution characteristics features in pre-monsoon and monsoon season for convective and stratiform precipitation of windward side of Western Ghats analysis, using long-term in-situ JWD instrument data done. Convective and stratiform rainfall classification is based on the number of concentrations of rain droplets and rain rates. Tropical Rainfall Measuring Mission (TRMM) and ERA-Interim data sets are also integrated with disdrometer data to establish microphysical and dynamical features of pre-monsoon and monsoon season rain. Long-term trends of rain droplet size spectra are not studied until now over the Western Ghats. Rain droplet spectra of pre-monsoon and monsoon seasons show notable differences. The rain droplets of monsoon display considerably higher divergence compared to pre-monsoon rainfall. Monsoon rainfall has a higher concentration of smaller drops, while pre-monsoon rainfall contains a significantly higher concentration of large droplets. RSD classified on the rain rate demonstrates a higher mass-weighted mean diameter (Dm) and a lower normalized intercept parameter (log10Nw) in monsoon than winter. Similarly, the Diurnal variation of RSD reveals higher Dm with a lower value of log10Nw in pre-monsoon season. Also, in both seasons, the higher value of mean Dm in convective precipitation than stratiform. Convective activities with increased ground temperature alter RSD in pre-monsoon season rather than monsoon season through droplet classification, evaporation, and collision-coalescence processes.

Deep convection is known to be critical for the transport of mass and momentum flux, heat and moisture throughout in the upper troposphere and lower stratosphere region. Hence it modifies the heat budget and general circulation in the atmosphere. Earlier studies have noted very strong instability in the atmosphere over Himalayan foothills, triggering occasional intense convection due to the orographic lifting of the low level moist flow. However due to the lack of observational network over this complex terrain, a comprehensive analysis of these events and their impacts have not been done.Recently a Stratosphere Troposphere Radar (wind profiler) operating at VHF frequency of 206.5 MHz has been installed at a high altitude site Aryabhatta Research Institute of Observational Sciences (ARIES) (29.4oN, 79.5o E, 1790 m amsl) in Nainital located in Himalayan foothills, a meteorologically sensitive subtropical region. Using the capability of VHF radar of detecting echoes from both clear air and precipitation, intense deep convection systems were observed on May 5, 2020 and September 2, 2020. Both the events have been studied in details using the temporal and vertical evolution of radar parameters like total backscattered power and spectral width. Reanalysis data from MERRA-2 and cloud fraction data of IR and Water Vapour channels of INSAT 3D has also been used to investigate underlying synoptic features of the event. Here, it is suggested that deep convection of the pre-monsoon season was induced due to moisture carried by the western disturbance. While the event in monsoon season was due to the easterly moist flow from the Bay of Bengal. The moisture in the mid - troposphere coupled with the orographic lift led to vigorous updrafts and downdrafts of magnitude reaching up to 16 m/s. Updrafts found to be extending well beyond the tropopause into the lower stratosphere region. From the temporal evolution of vertical wind velocity obtained from ST Radar, a clear demarcation between updrafts and downdrafts region was established during the mature phase of the event due to veering of the wind from lower to upper troposphere which also led to the tilting of the updraft cores. During the event the exchange of the vertical flux of horizontal momentum between upper troposphere and lower stratosphere has also been estimated. A significant enhancement (2 – 3 times) in mean zonal (u'w') and meridional component (v'w') of momentum flux has been observed during convection as compared to quiet period. In the upper troposphere and lower stratosphere region mean flux values even reached up to about 33 m2 s-2. We feel that this study will help in providing the crucial insights of the dynamical features of meso-scale convective phenomenon in the central Himalayan region for the first time.

Unsupervised learning techniques such as principal component analysis (PCA), cluster analysis (CA) were applied to the groundwater data of Mewat region (Haryana, India) collected in the pre monsoon season to identify the geochemical processes controlling groundwater chemistry. Thirteen physicochemical parameters were analyzed and were found to be above the permissible limits. The order of cation and anion concentration were found to be Na+ > Mg2+ > Ca2+ > K+ and Cl− > $${\text{NO}}_{3}^{ - }$$ > $${\text{SO}}_{4}^{2 - }$$ > $${\text{HCO}}_{3}^{ - }$$ > $${\text{CO}}_{3}^{2 - }$$ . The dominance of Na+ and Cl− in groundwater chemistry showed the salinity factor in the groundwater. PCA applied to the data set reduced the dimensionality to four significant factors accounting 76.66% of the total variance in the data set. The first factor can be assigned to alkalinity which originates due to the dissolution of geological minerals into the groundwater, second factor is assigned to salinity (due to salt water intrusion) and hardness which is caused by weathering of sedimentary rocks and calcium bearing minerals and other factors originate as a result of industrial wastes, domestic wastes and wastes from agricultural activities. CA classified 30 sampling sites into three clusters with relatively low salinity region, high salinity and very high salinity regions based on similar water quality characteristics.

RSPM (PM10) Gaseous pollutant like SO2, NO2 and Air Quality Index has been simultaneously measured during the pre-monsoon month of April and May 2019 at the busiest squares of Indore city which are Palasia and Palsikar. Sampling was conducted with the help of respirable dust sampler and was followed by CPCB norms. The lowest RSPM has been observed in the morning time at Palsikar square that is 61 µg/m3 and highest in the morning that is 123 µg/m3; similarly, at Palasia square the RSPM concentration in morning detected as lowest was 104 and 127 µg/m3 as highest during the month. At evening peak hours the concentration at Palsikar square have been observed 117 µg/m3 as lowest and 186 µg/m3 as highest. On the other end the concentration at Palasia square has been observed 181 µg/m3 as lowest and 187 µg/m3 as highest. It is observed that the gaseous pollutant concentration was lowest at Palsikar and highest at Palasia and AQI remains moderate except Palasia. This data can help to analyze the present status of vehicular pollution with the respective squares and can also help in the future for making some policies to prevent it.

Ammonium nitrate (NH4NO3) is the main driver of high PM2.5 episodes in Seoul, but its formation processes are not fully understood yet. Intensive experiments were conducted at the Korea University campus in Seoul during June ~ August 2018 and April ~ June 2019, when the chemical composition of PM2.5 including Na+, SO42-, NH3, NO3-, Cl-, Ca2+, K+, Mg2+, OC and EC, and its gaseous precursors including NOX, HNO3 and SO2 were continuously measured. The concentrations of PM2.5 and its major constituents were noticeably higher in pre-monsoon (June) than summer monsoon (July~August) period. In particular, nitrate concentration was much higher (6.9 μg/m3) during the high PM2.5 episode (24-hr average PM2.5 > 35 μg/m3) in June compared to those of non-episode (3.1 μg/m3) and the other two months (0.74 μg/m3). Aerosol liquid water content (ALWC) was calculated using ISORROPIA II model, ALWC was higher during the episode than non-episode and the highest ALWC was found concurrently with the highest NO3- concentration (18.2 μg/m3) at night. Concurrent increases of nitrate and ALWC cause aqueous-phase formation and hygroscopic growth of aerosol, which lead to high PM2.5 concentration. In addition, ALWC was more rapidly increased with the number of accumulation mode particles larger than 100 nm in diameter at higher RH and nitrate concentration. In this study, PM2.5 mass and nitrate were elevated after the NOX peak in the morning as well as at dawn. The surface of pre-existing particles was found to be prerequisite for nitrate driven PM2.5 episode.

Aerosol characteristics over Varanasi region during pre-monsoon (April - June) period were analyzed for year 2017. Aerosol optical properties and angstrom exponent were measured using MICROTOPS-II Sunphotometer. The mean AOD for the period of study was found to be 0.78 where as mean angstrom exponent (AE at 440 - 870 nm) was found to be 0.29. Average concentrations of PM 2.5 and PM 10 were found to be 38.15 ± 22.48 µg/m3 and 126.10 ± 45.39 µg/m3 respectively, which clearly demonstrates dominance of coarse mode particles particularly in this season.

Fine particulate matter (PM2.5) and surface ozone (O3) are major air pollutants in megacities such as Delhi, but the design of suitable mitigation strategies is challenging. Some strategies for reducing PM2.5 may have the notable side effect of increasing O3. Here, we demonstrate a numerical framework for investigating the impacts of mitigation strategies on both PM2.5 and O3 in Delhi. We use Gaussian process emulation to generate a computationally efficient surrogate for a regional air quality model (WRF-Chem). This allows us to perform global sensitivity analysis to identify the major sources of air pollution and to generate emission-sector-based pollutant response surfaces to inform mitigation policy development. Based on more than 100 000 emulation runs during the pre-monsoon period (peak O3 season), our global sensitivity analysis shows that local traffic emissions from the Delhi city region and regional transport of pollution emitted from the National Capital Region (NCR) surrounding Delhi are dominant factors influencing PM2.5 and O3 in Delhi. They together govern the O3 peak and PM2.5 concentration during daytime. Regional transport contributes about 80% of the PM2.5 variation during the night. Reducing traffic emissions in Delhi alone (e.g. by 50 %) would reduce PM2.5 by 15 %–20 % but lead to a 20 %–25 % increase in O3. However, we show that reducing NCR regional emissions by 25 %–30 % at the same time would further reduce PM2.5 by 5 %–10 % in Delhi and avoid the O3 increase. This study provides scientific evidence to support the need for joint coordination of controls on local and regional scales to achieve effective reduction in PM2.5 whilst minimising the risk of O3 increase in Delhi.

Remote Sensing is a very reliable and expeditious technique for assessment and mapping of surface waterlogged areas. In this study band ratio based NDWI index (Normalized Difference Water Index) was used for extracting water pixels from optical imageries. To overcome the limitation of false positives and cloud penetration associated with optical imageries waterlogged areas was also extracted using SAR (Synthetic Aperture Radar) images. Thresholding of NDWI for optical image and Sigma0 for SAR images was done using their respective histograms to distinguish water and terrestrial features. The total surface waterlogged areas in the district was calculated by integrating the results from both optical and SAR images. It was found that surface waterlogged areas varies temporally from pre-monsoon to post-monsoon period in Rohtak district, Haryana. The surface waterlogged area for pre monsoon period is around 9.7 km2 and for post monsoon period is 17.86 km2. The canal and surface drain network in the district was digitized using the high resolution Sentinel 2 MSS images. Since most of the canals in the area are unlined a buffer of 500 m either side of the canals and surface drains was considered to assess the impact of seepage and leakage from canals and surface drains. It was found that more than 50% of the total surface waterlogged areas fall within this buffer, clearly indicating the contribution of leakages from canals and surface drains on surface waterlogging.

The ultrafine particle number concentration and size distribution during pre-monsoon (spring) over a high altitude location, Ooty (11.3 °N, 74.4 °E, 2240 m amsl) in Western Ghats, the highest peak in South India, are examined using campaign based ground observations. The total number concentrations are in the range ∼1000–3000 cm−3 with significant increase (2–4 folds) during the periods of ultrafine particle (UFP) (diameter

Deadliest tropical cyclones (TCs) with category 4 or 5 intensity, which are referred to super TCs (STCs), often take place in Bay of Bengal (BoB) during pre-monsoon transition period. These STCs are often synchronized with the first-branch northward-propagating intraseasonal oscillation (FNISO) over BoB, but not all TCs synchronizing with FNISO were able to develop into STCs. The study analyzes the distinctive environmental conditions for regular and super TC groups. From the intraseasonal background, the most important difference appears in the intensity and relative location of FNISO. A stronger and closer ISO would lead to a colder upper-level air temperature and thus a more unstable stratification which promotes a greater TC intensity. Similar to intraseasonal timescale, upper-level temperature on the interannual timescale is also colder in the STC cases. The combined intraseasonal and interannual environmental temperature difference between lower and upper troposphere are responsible for significant difference between the STC and TC cases.

This study focuses on exposures of metal constituents of particulate matter (PM) in the ambient air sample collected at Indian Institute of Technology Delhi (IIT Delhi), India, which might lead to occurrence of non-cancerous events and cancer events. A step-wise construction of risk assessment framework for estimating risks due to exposures of PM2.5 presented. Samples from winter and pre-monsoon seasons of Delhi region (28.5450°N, 77.1926°E) (duration 1: December 2013–February 2014; duration 2: March 2014–May 14) were collected. More than 12 samples were collected using PM2.5 sampler on an 8-h basis and analysed gravimetrically for determining mass content and chemically for determining metal content of PM2.5. Twenty-eight metals in samples were detected using Energy Dispersive X-Ray Fluorescence (ED-XRF). Using these values, health risks of hypotheticals exposures of PM2.5 in ambient air samples were estimated either in terms of hazard quotient (i.e. ratio of daily inhaled dose to daily acceptable dose) for exposures of non-carcinogenic metals or lifetime excess risk of cancer for exposures of carcinogenic metals. Dose–response information of different metals was taken from the U.S. EPA IRIS database. Among metals, S content was highest followed by Cl, Si, K, Ca and Fe, Zn and Pb. High S can be attributed to vehicular emission or particles generated from abrasion of tyres of vehicles. High contents of Si, Ca, Fe in PM samples may be contributed from resuspension road dust, while source of K may be local biomass burning for space heating in winter. Zn comes from vehicle and coal burning probably used by local residents for space heating. Chlorine used in lubricants and diesel fuel could be a source of high Cl content in samples collected in the present work. Small traces of Pb in samples might be coming from brake and tyre wear or resuspension of road dust contaminated with lead used earlier in diesel and/or petrol to improve combustion. Estimates of potential risk due to hypothetical exposure of adults and children to four carcinogenic metals of PM2.5 were found to be more than 1/10,000,000, indicating chance of cancer risks. Among metals, exposures to PM-associated Cd resulted in consistent cancerous risk in both seasons, whereas exposures to PM-associated Cr resulted in HQ value > 1 indicating chance of non-carcinogenic risks.

An evidence of a changing climate is already sensed in India where there is a large diversity from region to region and from season to season. The rainfall pattern in the pre-monsoon (March–April–May) season is important as it helps in determining many crop-related activities in many parts of the country. In the present study, an attempt is made to analyze the current trends in pre-monsoon season rainfall and temperatures over 34 meteorological subdivisions in India using the India Meteorological Department observed analysis datasets of rainfall (1951–2013) and temperatures (1981–2013). The results suggest that a significant decreasing trend in the pre-monsoon rainfall at all-India level and the maximum reduction is found in the month of March. From the regional scale analysis, the south peninsular India is found to have an increasing trend, whereas a decreasing trend is observed over Jammu and Kashmir, Himachal Pradesh and northeast parts of the country. The analyses reveal an association of pre-monsoon rainfall over India with precipitation over China and temperature over the South China Sea, which may act as a precursor for the pre-monsoon rainfall that ultimately could affect the Indian summer monsoon rainfall. The increase of rainfall activity over south peninsular India is attributed to increases in the meridional temperature gradient with an increase of specific humidity. The results of the study will be useful for a long-term risk management in various sectors and would aid in adapting new technologies for a sustainable development in the changing climate scenario.

Spatio-seasonal water presence frequency and water depth change is tried to identify in two manmade reservoirs (Massanjore dam and Tilpara barrage) over Mayurakshi river of Eastern India. These reservoirs use to supply water for hydroelectricity and irrigation services. Multi-temporal image base analysis in three phases (phase 1:1987–1999; phase 2: 2000–2006 and phase 3: 2007–2016) clearly depicted that (1) in case of Massanjore dam (67.4 km2) water presence area in pre-monsoon season is declined from 44.13 to 23.54 km2 in between phase 1 and 3. (2) In post monsoon season, same is declined from 63.37 to 37.57 km2. (3) In case of Tilpara reservoir, water presence area is declined from 3.61 to 2.20 km2 in pre monsoon season and 3.76–2.67 km2 during post monsoon season since phase 1–3. Both average and maximum NDWI scores indicating qualitative depth of water in pre and post monsoon seasons have declined over time with significant rate (R2 ranges from 0.42 to 0.58). All these indicate growing attenuation of water availability within reservoirs. This may invite hardship to the stakeholders depends on the reservoir and ecological set up of the reservoir.