Impact of Dust Storm on the Atmospheric Boundary Layer over Ahmedabad, a Western Indian Region .

Abstract

The present study focuses on investigating the impacts of a sudden dust storm on the atmospheric boundary layer (ABL) over Ahmedabad (23.02°N, 72.57°E), an urban site located in the western region of India. The accumulation of dust in the atmosphere during the dust storm, originating from the Thar Desert in Rajasthan, led to the decrease in surface temperature as a consequence of dust-radiation interaction. Ambient particulate matter data obtained from Air Quality (AQ) station at Ahmedabad showed a spike of 118.5% and 44.5% in PM10 and PM2.5 concentrations, respectively during the event in comparison to the previous control day. Sudden exposure to an anomalous increase in particulate aerosols may cause severe impacts on human health. These surface forcing have been reflected in the stable nocturnal ABL. Backscatter signals recorded by ground-based Ceilometer Lidar at Physical Research Laboratory (PRL), showed that ABL was shallow and collapsed during the dust storm episode. Turbulence was detected in the ABL during the event which further assisted in the vertical mixing of dust aerosols in the ABL. These aerosols got trapped within the residual layer, preventing further percolation in the free atmosphere. Such sub-grid scale changes in the ABL during the dust storm were not reflected in the boundary layer height (BLH) obtained from the ERA-5 reanalysis dataset. A significant association between the ABL and the local radiative budget has been found. It has been substantiated by Coupled Ocean-Atmosphere Radiative Transfer Model (COART) simulations that showed a cooling of the surface. Thus, this study is important as it can be taken as feedback to improve local climate models with respect to dust storm meteorology.