Vertical Distribution of Aerosols During Deep-convective Event in the Himalaya Using WRF-Chem Model at Convection Permitting Scale

Abstract

The Himalayan region is facing frequent cloud burst and flood events during the summer monsoon e.g., Kedarnath flood of 2013. It was one of the most devastating event which claimed thousands of human lives, heavy infrastructure and economic losses. Fast moving monsoon, pre-existing westerlies, and orographic uplifting was reported as the major reason for cloud burst over Kedarnath in previous research. Our study illustrates the vertical distribution of aerosols during this event and its possible role using Weather Research and Forecasting model coupled with chemistry (WRF-Chem) simulations. Model performance evaluation shows that simulations can capture the spatial and temporal pattern of observed precipitation during this event. Model simulation at 25km and 4km horizontal grid resolution without any changes in physical parameterization shows very minimal average difference in precipitation. Whereas simulation at convection permitting scale shows de-tailed information related to parcel motion compared to coarser resolution simulation. This indicates parameterization at different resolution needs to examine for better outcome. The result shows up to 20-50% changes in rain over area near Kedarnath due to the presence of aerosols. The simulation at both resolution shows significant vertical transport of natural (increases by 50%+) and anthropo-genic aerosols (increases by 200%+) during the convective event. Which leads to significant changes in cloud property, rain concentration and ice concentration in presence of aerosols. Due to aero-sol–radiation feedback, the important instability indices like convective available potential energy, convective inhibition energy, vorticity etc. shows changes near Kedarnath.