Impacts of a Mesoscale Dust Storm on Aerosols Characteristics, Optical and Radiative Properties Over a Semiarid Region, Western India

This paper investigates the impacts on aerosol characteristics, optical and radiative properties due to a mesoscale dust storm which originated from the Arabian, Iran/Pakistan region and observed to pass in vicinity over the semiarid region of Western India in April, 2017. The extent and long-distance transport of dust along with varying aerosol optical depth (AOD) were studied with high spatial and temporal resolution space-based observations. In situ measurements of particulate matter (PM) indicated high dust loading with PM10 and PM2.5 concentrations as high as 223 and 253 mu g/m(3) and 142.6 and 160 mu g/m(3), respectively. High concentrations of Inhalable, thoracic and alveolic PM aerosols (similar to 290, 200 and 100 mu g/m3, respectively) are also observed due to high dust load in the atmosphere, that is hazardous to human health, particularly for people suffering from respiratory ailments. The fine-mode fraction and Angstrom exponent have also been analyzed using satellite data. Satellite-derived AOD and in situ meteorological data were used as model inputs to estimate the radiative forcing impact of dust aerosols using a coupled radiative transfer model. The radiative transfer model simulations results indicate a reduction in the total downward surface flux by 6.5%, 6.7%, 5.0%, 10.1%, 7.1%, 8.9%, 3.7% and 5.3% as height decreases from 5 to 0 km (surface) during pre- to post-dust storm event period, respectively. The aerosols vertical profiles obtained from spaceborne CALIPSO LiDAR validated the predominant presence of "dust'' aerosols during this event. The study provides important quantitative insights into extreme variabilities in aerosol properties resulting to a "cooling effect'' during a severe mesoscale dust storm event over a semiarid region.