Contrasting impacts of net cloud radiative forcing on the surface temperature trends in India

Abstract

The rise of spatial heterogeneity in surface temperature (Ts ) over India cannot be explained by only the direct effect of enhanced greenhouse gas forcing. Here we propose an analytical framework to estimate the impact of the net cloud radiative forcing (CRF) trend on the observed Ts trend for the duration of 2000-2019. The cloud sensitivity (λcld ) estimated from the satellite observations vary in the range -0.180 to 0.241 K per W m-2 across the seven Ts homogeneous zones in India. Net average (±1σ) CRFs over the Indian landmass during 2000-2019 in the shortwave and longwave are -15.5±11.3 and 12.4±7.4 W m-2, -28.1±22.4 and 24.6±9.8 W m-2, -75.1±20.4 and 55.0±13.8 W m-2 and -23.3±14.9 and 21.6±14.8 W m-2, respectively for the winter (Dec-Feb), pre-monsoon (Mar-May), monsoon (Jun-Sep) and post-monsoon (Oct-Nov) seasons. We find that in some of the Ts homogeneous regions, seasonal Ts trends are suppressed, whereas in some other Ts homogeneous regions, seasonal Ts trends are accelerated by the net CRF. Our framework can be useful in studying the role of clouds in observed surface warming trends.