The study investigated the spatio-temporal variations of aerosol and cloud properties retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite at an urban megacity Delhi in the northern part of India during the dry and wet seasons for 15 years period from November 2004 to October 2019. This research comprises the study of crucial aerosol optical properties such as aerosol optical depth (AOD), Angstrom exponent (AE) along with the cloud properties such as water vapor (WV), cloud liquid water path (CLWP), cloud effective radius liquid (CERL), cloud fraction (CF), cloud optical depth (COD), cloud top pressure (CTP), and cloud top temperature (CTT). High AOD was observed across the Indo-Gangetic Plain (IGP), including Delhi and exhibited a range of 0.49 to 0.89 during dry season and 0.73 to 0.98 during the wet season with a mean of 0.73±0.05 during the entire study period. High AE value (mean 1.40±0.05) indicates dominance of fine-mode aerosols over the station, associated with high anthropogenic activities. A significantly large increasing trend in AOD was observed over the station during the wet season as compared to the dry season. The seasonal studies represent the maximum value of WV and CTP in the wet season. In addition, CF, CERL, COD and CLWP values were also high during the wet season. Furthermore, a correlation analyses between the aerosol and cloud parameters were carried out during the dry and wet seasons. From the analysis, AOD shows a positive correlation with WV, CF, COD and CLWP during both the seasons whereas a negative correlation was observed with CTP in wet season, while positive in dry season. On the other hand, a poor correlation was observed between AOD verses AE and CTT in both the seasons. These findings can contribute to advancing our understanding of aerosol-cloud interactions and inflate air quality assessments at an urban megacity like Delhi.

This research focuses on using artificial neural network (ANN) models to assess daily surface PM (2.5)concentrations by incorporating aerosol optical depth (AOD) and cloud parameters from the Moderate Resolution Imaging Spectroradiometer (MODIS), along with meteorological data, for the period from January 2017 to December 2021 over Kanpur. For this exercise, three ANN models were utilized: ANN1 (1 Layer, 14 Neurons), ANN2 (2 Layers, 14, 28 Neurons), and ANN3 (1 Layer, 14, 28, 14 Neurons). Statistical tests such as FAC2, MGE, NMB, MAPE, RMSE, R, and COE were conducted to validate the models. Initial results show that the ANN1 performed the best. The study also examined spatial and temporal changes to observe variations in PM2.5, AOD, and various cloud properties, including water vapor (WV), cloud effective radius (CER), cloud fraction (CF), cloud liquid water path (CLWP), cloud optical depth (COD), cloud top pressure (CTP), and cloud top temperature (CTT) on a seasonal and annual basis, as well as during high PM (2.5) concentration conditions. During the study, the average daily PM(2.5)was found to be approximately 100 mu g/m3 (ranging from 0.45 to 470.23 mu g/m3), while the average AOD was 0.79 (ranging from 0.09 to 3.55). High PM (2.5) concentrations (three to five times higher than the NAAQS annual limit) significantly influenced crucial cloud microphysical properties. The research findings aid in estimating PM (2.5) using satellite-retrieved AOD and meteorological data, providing insights into aerosol and cloud properties variability during high pollution events in the heavily polluted city of Kanpur, India.

The review paper delves into the intricacies of water quality index (WQI) and its relationship with land use and land cover in the Ganga River basin of Uttar Pradesh. The study highlights the significance of the Ganga River, a major perennial river in India, and presents findings from previous paper work shows that 57 sites of Ganga basin show fair, poor, or heavily polluted water quality. Analysis of live storage data within the basin revealed a notable increase in LULC compared to previous years, resulting in decrease water quality indicators such as low rate of dissolved oxygen (DO) levels and high concentrations of pollutants like faecal coliform, total coliform, and nitrate (NO3-). The observed increased in nitrate concentration, particularly attributed to enhance industrial activities and agricultural runoff during the harvesting season, suggests a negative trend towards water quality restoration. The prevalence of untreated commercial and industrial wastewater remains a significant challenge to sustained water quality improvement. In conclusion, the paper advocates for addressing land use land cover of the Ganga basin and ensuring adequate flow releases to rejuvenate the river effectively. It underscores the need for comprehensive measures to sustainably manage land use and cover water resources and mitigate anthropogenic impacts on the middle Ganga River.

Measurements of near-surface air pollutants at an urban station, Lucknow have been studied at two contrasting sites as residential and industrial during three-year period from 2015 to 2017 to understand their variability on different temporal scales. The annual mean mass concentrations of sulphur dioxide (SO2), nitrogen dioxide (NO2), nitric oxide (NO) and particulate matter of size less than 2.5 µm (PM2.5) at an industrial site were about 10 ± 5, 28 ± 17, 10 ± 11 and 128 ± 99 µg m-3 and at the residential site were about 8 ± 5, 30 ± 21, 9 ± 7 and 102 ± 81 µg m-3 respectively. It was observed that the annual mean mass concentration of PM2.5 was about 3 times higher than its annual National Ambient Air Quality Standards (NAAQS) level. However, SO2 and NO2 were about 5 and 1.5 times lower to their annual NAAQS levels, respectively. The seasonal mean mass concentrations of all the pollutants were found to be highest during the winter/post-monsoon season at both the sites, which are more pronounced at industrial site compared to residential site. The observed high pollutants over the station during the winter/post-monsoon season were found to be largely associated with the air mass back-trajectories from N-NW direction.

Short-wave incoming solar radiation and aerosol optical characteristics were examined at New Delhi, in the western Indo-Gangetic Basin (IGB) for the period from March 2010 to June 2012 to understand their possible association in different sky conditions along with their radiative implications. During the study period, solar radiation varied between 65 and 624 Wm(-2), with a seasonal mean of 419 +/- 34, 328 +/- 32, 308 +/- 54 and 306. 56 Wm(-2), respectively in the summer, monsoon, post-monsoon and winter periods. Inter-annually, the magnitude of solar radiation was similar to 19% and 23% higher during 2012 as compared to 2011 and 2010. Aerosol optical Depth (AOD) varied between 0.11 and 2.4 (mean: 0.69 +/- 0.38) whereas Angstr_om Exponent (AE) was between 0.46 and 1.81 (mean: 0.8 +/- 0.28) during the entire study period. The solar radiation was found to be significantly correlated with the AOD (R = -0.22) and AE (R = -0.45). The mean characteristics of solar radiation and aerosol optical parameters were found to differ significantly in different sky conditions, which were used to examine their possible implications to direct radiative effect (DRE). The DRE at the surface was as high as about -19 W m(-2) during clear sky day, which was similar to 16 and 48 W m(-2) higher than that of haze/foggy and dusty days, respectively.

Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)-derived aerosol vertical profiles were studied in the upper troposphere and lower stratosphere (UTLS) over the Indian summer monsoon (ISM) region during two successive and contrasting monsoon years (2008-2009). An enhanced aerosol layer was observed in the UTLS between 15 and 19 km altitude, in the vicinity of tropopause during both years. However, the optical characteristics of aerosol layers were found to be dissimilar during the two contrasting consecutive summer monsoon seasons. While the depolarization ratio of enhanced aerosol layer (exceeding 0.2) during both years suggested anisotropic nature of particles, the aerosol backscatter coefficient was observed to be more intensified with a sharp peak during the active monsoon year (2008) whereas it was relatively broader with lower magnitude during a drought year (2009). The enhanced backscatter coefficient in the UTLS was found to be closely associated with the variability in tropopause height and convection during both years, which is more pronounced during the active monsoon year as compared to a drought year. Deep convection over the ISM region may inject boundary layer aerosols into the upper troposphere as evidenced from the analysis of the outgoing long-wave radiation (OLR). Our results also showed an enhanced integrated backscatter coefficient (IBC) of about 30%, which is associated with a decrease in OLR of about 7% during the active monsoon year as compared to drought year. These findings were further corroborated using NCEP-NCAR vertical velocity and HYSPLIT air-mass backward trajectory analyses.

Aerosol measurements over an urban site at Delhi in the western Ganga basin, northern India, were carried out during 2009 using a ground-based automatic sun/sky radiometer to identify their different types and to understand their possible radiative implications. Differentiation of aerosol types over the station was made using the appropriate thresholds for size-distribution of aerosols (i.e. fine-mode fraction, FMF at 500 nm) and radiation absorptivity (i.e. single scattering albedo, SSA at 440 nm). Four different aerosol types were identified, viz., polluted dust (PD), polluted continent (PC), mostly black carbon (MBC) and mostly organic carbon (MOC), which contributed ~48%, 32%, 11% and 9%, respectively to the total aerosols. Interestingly, the optical properties for these aerosol types differed considerably, which were further used, for the first time, to quantify their radiative implications over this station. The highest atmospheric forcing was observed for PC aerosol type (about +40 W m(-2), along with the corresponding atmospheric heating rate of 1.10 K day(-1)); whereas the lowest was for MBC aerosol type (about +25 W m(-2), along with the corresponding atmospheric heating rate of 0.69 K day(-1)).