Simulating winter and summer AOD with Chimere-optsim: improved prediction over India

Abstract:

Aerosol Optical Properties (Aerosol Optical Depth (AOD) and Single Scattering Albedo (SSA)) were simulated over India using a high resolution coupled regional chemical transport model WRF-Chimere. The simulations were done for all months of winter (November-February) and pre-monsoon(April, May) seasons using two emission inventories, SMOG (Speciated Multi-pollutant Generator from Indian Institute of Technology Bombay) and newly made constrained emission. Comparison with the satellite observation MODIS (Moderate Resolution Imaging Spectroradiometer), revealed underestimation in the range of 80% to 150% over North-Western part and 30% to 50% over the rest part of India in case of SMOG emission. In case of constrained emission, modeled AOD bias was found to be reduced with underestimation range of (10%-30%) over North-Western part and overestimation range of (10%-20%) in the other parts of India . Due to very low observed AOD, high overestimation was seen in some regions of the eastern coast . The seasonal mean of simulated AOD (550 nm), with constrained emission, showed bias in the range of -30% to 30% over most parts of India except at some parts of south India and central India. Modelled seasonal mean AOD agreed well with seasonal mean ground-based measurement (Aerosol Robotic Network (AERONET)) with bias in the range of 1% to 25% at eight different stations. Modelled SSA, with each emission inventories, showed underestimation (1% - 25%) at all stations. Similar to observation (MODIS), the model is able to captured the general features of spatial variation in AOD, i.e. comparatively high AOD over Indo Gangetic plain.