Changes in aerosol parameters during major dust storm events (2001–2005) over the Indo‐Gangetic Plains using AERONET and MODIS data

Abstract

The Indo‐Gangetic (IG) plains is one of the largest and most densely populated regions in the world. Recent studies over the IG plains using multi‐year (2000–2004) satellite (including Moderate Resolution Imaging Spectroradiometer: MODIS) and ground Aerosol Robotic Network (AERONET) data show strong seasonal variability of aerosol optical depth (AOD) with maximum aerosol loading (>0.6–0.7 at 500 nm) during the pre‐monsoon (summer) season. A number of major dust storms, originating from western arid and desert regions of Africa, Arabia and western part of India (Thar Desert), affect the whole IG plains during the pre‐monsoon season (April–June). The mean AOD increases from 0.4–0.5 to more than 0.6–0.7 throughout the plains (>0.8–0.9 on the western side) as a result of the dust storm events. Pronounced changes in the aerosol optical parameters, derived from AERONET, have been observed over Kanpur (26.45°N, 80.35°E) during dust storm events (2001–2005). The maximum AOD (at 500 nm) during dust event days show increase from ∼1 to ∼2.4 with advance of the pre‐monsoon season (April–June). The aerosol size distribution (ASD) shows increase in radius from 1.71 to 2.24 μm (in coarse fraction) and decrease in the distribution width from 3.76 to 2.56 μm showing changes in the aerosol characteristics during dust events. The aerosol parameters [ASD, single scattering albedo (SSA, total and coarse mode) and real and imaginary parts of the refractive index] change significantly during dust events. The National Oceanic and Atmospheric Administration (NOAA) Hybrid Single‐Particle Lagrangian Integrated Trajectory (HYSPLIT) model (5‐day back‐trajectory) and MODIS level‐3 daily data (AOD and Ångström exponent) have been used to trace the source, path and spatial extent of dust storm events. During major dust events, enhancement of the total column water vapor is observed from MODIS level‐3 daily water vapor data (near‐infrared clear column) showing a strong association (72% correlation) with the AOD along the track of dust storms over the IG plains. A significant rise of 50–100% is observed in the ground level respirable suspended particulate matter (RSPM) concentration showing alarming health risks to the people living in the IG plains during dust storm events.