Quantification of long-range transported aeolian dust towards the Indian peninsular region using satellite and ground-based data - A case study during a dust storm over the Arabian Sea

The Arabian Sea is an enclosed basin surrounded by land and is prone to receive large amount of aeolian dust from the continent. This can significantly impact surface water biogeochemical processes. In this study, an attempt has been made to quantify the amount of dust transported from Middle East region to Indian subcontinent (sampling site is Goa; 15.45 degrees N 73.80 degrees E; located in the northeast Arabian Sea) via the Arabian Sea. We identified a dust storm episode (02-10 April 2015) in the Arabian Peninsula and its propagation to the study site (Goa) using satellite data (MODIS and CALIPSO). The impact of the dust storm at Goa has been computed using ambient particulate matter concentration and satellite retrieved optical parameter. These observations were further substantiated using ground-based micro-pulse lidar measurement. The daily averaged lidar profile shows relatively high depolarization ratio (0.1-0.25), as well as high daily average backscatter coefficient (up to 0.08 Sr-1 Km(-1)) and extinction coefficient (up to 0.9 Km(-1)) during the storm period compared to non-dusty days. During this period, a two-layer (rich in non-spherical particle) structure with significantly high linear depolarization ratio is observed, indicating the impact of the dust storm at the coastal region of India. Ambient mass concentration of dust estimated using CALIPSO profile are comparable with the gravimetric mass measured from high volume sample collection. The back-trajectory analysis further supports the advection of air-mass from the Middle East to Eastern Arabian Sea. This study highlight the significant role of long-range transport in impacting dust load at the remote/receptor sites.