Multi year measurements of surface-reaching solar (shortwave) radiation fluxes across a network of aerosol observatories (ARFINET) are combined with concurrent satellite (CERES)-based top of the atmosphere (TOA) fluxes to estimate regional aerosol direct radiative forcing (ARF) over the Indian region. The synergistic approach improves the accuracy of ARF estimates, which otherwise results in an overestimation or underestimation of the atmospheric forcing. During summer, an overestimation of similar to 5 W m(-2) (corresponding heating rate similar to 0.15 K day(-1)) is noticed. The regional average ARF from the synergistic approach reveals the surface forcing reaching -49 W m(-2) over the Indo Gangetic Plains, -45 W m(-2) over northeast India, -34 W m(-2) over the southern Peninsula, and - 16 W m(-2) in the oceanic regions of the Bay of Bengal. The ARF over the northern half of the Indian subcontinent is influenced mainly by anthmpogenic sulfate and carbonaceous aerosols. Dust is dominant in the western region of India during MAM and JJAS. Overall, the clear sky surface reaching solar radiation fluxes is reduced by 3-22% due to the abundance of aerosols in the atmosphere, with the highest reduction over the IGP during autumn and winter.

Twelve years of NASA CERES (Clouds and Earth's Radiant Energy System) data have been used to examine the spatio-temporal variability of aerosol - and cloud - induced shortwave radiative forcing over selected hot spot regions in India. Four regions (northern semiarid - R1; monsoon trough - R2; densely populated urban - R3; and southern peninsula - R4) are selected with different surface characteristics and notable difference in meteorological and geographical features. The analysis shows that three out of the four regions (viz. R1, R2, and R3) experience high aerosol loading and forcing in the monsoon season followed by moderate forcing in pre-monsoon season. While all the seasons except the post-monsoon period show a positive linear relation between cloud optical depth and aerosol optical depth for all the regions, the post-monsoon season shows a negative relation. However, the relation between aerosol forcing and cloud forcing shows adequate non-linearity owing to the numerous factors that control cloud radiative effect. The estimated aerosol induced heating rate shows exponential decrease with height, but with high variability during each season. Irrespective of any region, the maximum heating rate is observed in the pre-monsoon season (2.86 +/- 0.78, 2.49 +/- 0.78, 1.89 +/- 0.57, and 0.88 +/- 0.28 K/day for R1, R2, R3, and R4, respectively). Plausible reasons for the variation in the above parameters are discussed. The results suggest that increased anthropogenic activities affect the thermodynamics and hence the dynamics through retention and exchange of heat, and it could affect the precipitation pattern adversely. (C) 2019 COSPAR. Published by Elsevier Ltd. All rights reserved.