Abstract View
Sensitivity of the Hydrological Cycle to Aerosol Type and Amount Using High Resolution Weather Research and Forecasting Model over India
SAUVIK SANTRA, Shubha Verma, Roxy Mathew Koll, Olivier Boucher, Indian Institute of Technology Kharagpur
Abstract Number: 625
Working Group: Aerosols, Clouds and Climate
Abstract
An inconsistent prediction of aerosol species distribution over the Indian subcontinent has so far limited the understanding of their potential linkage to the observed regional signals of changing spatial patterns of Indian summer monsoon (ISM) rainfall over the recent years, comprising of both enhancing and weakening effects. The present study is aimed to provide a quantitative prediction of the comparative impact of aerosol types on the changing pattern of ISM rainfall over recent years. Here we show a spatial concordance between the regional signals of ISM rainfall as visualized in the temporal trend (2000-2019) of the Indian Meteorological Department (IMD) ISM observations, the Multi-angle Imaging Spectroradiometer (MISR) aerosol optical depth (AOD), and the adequately simulated aerosol species distribution. The spatial distribution of aerosol species were estimated using constrained aerosol estimation which could well represent the measured values across the Indian subcontinent. We executed high resolution WRF aerosol radiative feedback simulation to examine the governing mechanism to the sensitivity of ISM rainfall regional signals to aerosol species types. A significant increase in rainfall with respect to no aerosol scenario was identified along the western coast of India due to combined aerosols (both anthropogenic and dust), which is notably in line with the current observations of high rainfall incidents over the region. Overall an increase and decrease in the ISM rainfall was observed over the northwestern India region (NWI) and Indo-Gangetic plain (IGP) region respectively, being spatially concordant to respectively abundant dust aerosols and anthropogenic aerosols (mostly sulfate aerosols). The potential governing mechanism to contrasting features of changing ISM rainfall distribution was attributed to the enhanced regional evaporation rate due to dust induced weakening of the surface cooling over the NWI region compared to that due to aerosols induced potential suppression of the effective evaporation over the IGP region.