Ground and satellite based measurements show significant loading of atmospheric aerosols over the highly populated Indo-Gangetic Plains with implications to both air quality and regional climate. Recent studies have found varying trends in aerosol loading over this region during different seasons. However, most of these trends were associated or linked to changes in the strength of emission sources of both natural and anthropogenic origin. In this study, using data from multiple satellites (MODIS and MISR) and reanalysis (ECMWF, NCEP) products, we show that emission characteristics over the West or North-western part of India have significant impact on aerosol loading over the IGP irrespective of the seasons. Though it is known that variability in a combination of meteorological parameters impact aerosol loading conditions, we show that it is possible to explain them by using just the wind speed as a proxy. This shows that even slight changes to emission over Northwestern part of the Indian region may have significant impact on aerosol loading conditions over IGP with implications to air quality and regional climate.
A synergistic use of satellite and ground based remote sensing data has been utilized to analyze recent changes in the aerosol column loading over the Indo Gangetic Plain (IGP). Despite an overall statistically significant increase in the trend of annual mean aerosol optical depth (AOD) over the past decade, a prominent difference within seasons was observed. Summer and monsoon seasons have a slight decreasing trend, while post monsoon and winter have significant increasing trend. The optically equivalent composition inferred from ground based long term measurements of aerosol size and absorption characteristics reveals that summer and monsoon season are mostly dust dominated. Whereas, post monsoon and winter seasons are dominated by black carbon (BC) and/or other absorbing aerosols. We find that the observed decrease in AOD is associated with decrease in dust loading in the atmosphere with a large spatial extent covering the whole of North-Western part of India and IGP. Similar changes are associated with absorbing carbonaceous aerosol species during the periods showing an increasing trend. The decreasing dust loading over Indian region during summer along with increase in absorbing black carbon aerosols during the pre-monsoon and the monsoon period may have significant impact on aerosol radiative forcing and hence Indian summer monsoon rainfall.
The impact of rapid urbanization in cities on their microclimate is at present a great cause of global concern. One of the major consequences is the unexpected rise in temperatures in the cities compared to their surrounding areas, termed as the Urban Heat Island (UHI) effect. Over the past many years, several Indian cities are under severe stress owing to such extreme anomalous changes in their micro-meteorological conditions making them unfriendly for habitation. Presented here is a case study on Bhubaneswar - one such city on the east coast of India undergoing rapid urbanization in recent times. In this study, Land Surface Temperatures (LST) from MODIS Terra and Aqua instruments at 1 km<sup>2</sup> spatial resolution along with the Land Use and Land Cover (LULC) change data from Landsat was used over a 25 km radius about the city for a 15 years' period from 2000 to 2014. Preliminary analyses indicate spatio-temporal changes in LULC to be one of the primary and significant factors responsible for changes in the UHI effect over the city. Investigations on the spatio-temporal variations in LST across the city and its relationship with vegetation cover indicate that overexploitation of various resources demanded by a fast growing population has led to significant changes in LULC patterns in the last few years. Analysis of the changes in the urban energy balance and resulting UHI effect across the city under various urban growth scenarios and different proportions of green urban area are in progress.