Hotspot analysis and long-term trends of absorbing aerosol index from dust emissions measured by the Ozone Monitoring Instrument at different urban locations in India during 2005–2018

Abstract

The dust storm is a natural hazard and knowledge of hotspots of dust emission is important to improve forecasting the dust events by numerical models of climate and air quality. The absorbing aerosol index (AAI) observations derived from the Ozone Monitoring Instrument (OMI) sensor are analyzed over India covering the period from 2005 to 2018. In this manuscript, the hotspot analysis of AAI was conducted using the spatial autocorrelation technique for different seasons. The results showed significant spatial and temporal variability in the observed AAI. During pre-monsoon, the hotspot region is widely distributed, though with noticed spatially varying intensities, from the Thar Desert to West Bengal through the Indo Gangetic Plain (IGP) region. It is revealed from the back trajectory analysis that the airmasses were originated from the arid desert regions located in the West of India transporting the dust particles during the pre-monsoon over the IGP regions. Further, the trend analysis of AAI during the pre-monsoon over selected metropolitan in India was done using the Mann–Kendall (MK) test and Sen's robust slope estimator. The results showed a significant increasing (0.02 yr−1) and decreasing (−0.01 yr−1) trend in AAI at Patna and Hyderabad, respectively, while it is noticed stable or no trend at other cities. MERRA-2 Dust aerosol optical thickness was found to be very well correlated with AAI and shows decreasing and increasing trends at Nagpur (0.0005 yr−1) and Jaisalmer (0.004 yr−1), respectively. A negative correlation is observed between rainfall and AAI, indicating the reduction of AAI with increasing rainfall.