Abstract
The present study focuses on investigating the impacts of a sudden dust storm on the atmospheric boundary layer (ABL) over Ahmedabad (23.02 degrees N, 72.57 degrees E), an urban site located in the western region of India. The accumulation of dust particles 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 with the previous control day. Sudden exposure to an anomalous increase in the particulate matter may cause severe impacts on human health. These surface forcings 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 has been detected in the ABL during the event which further assisted in the vertical mixing of dust particles in the ABL. These dust particles 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. Coupled Ocean-Atmosphere Radiative Transfer Model (COART) simulations substantiated or showed a cooling event of the surface during the dust storm. This study is important as it can be taken as feedback to improve local climate models with respect to dust storm meteorology.