Abstract
Desert dust over the Indian region during pre-monsoon season is known to strengthen monsoon circulation, by modulating rainfall through the elevated heat pump (EHP) mechanism. In this context, an insight into long term trends of dust loading over this region is of significant importance in understanding monsoon variability. In this study, using long term (2000 to 2015) aerosol measurements from multiple satellites, ground stations and model based reanalysis, we show that dust loading in the atmosphere has decreased by 10 to 20% during the pre-monsoon season with respect to start of this century. Our analysis reveals that this decrease is a result of increasing pre-monsoon rainfall that in turn increases (decreases) wet scavenging (dust emissions) and slowing circulation pattern over the Northwestern part of the sub-continent.
Highlights
Apart from aerosol parameters we have used rainfall from Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Climatology Project (GPCP) to understand the impact of rainfall changes on the dust loading
The atmospheric aerosol loading over Northern Indian subcontinent is decreasing during pre-monsoon season
This decrease is due to change in dust emission over the arid and desert regions over North western part of Indian subcontinent including Thar Desert
Summary
The atmospheric aerosol loading over the Indian region peaks during the pre-monsoon (March to May) and the monsoon (June to August) seasons depending on location of interest and the spatial distribution of rainfall[49,54,55,56]. The increasing economic activities and resultant anthropogenic emissions render the possibility of a decrease in BC a remote possibility This is evident from the trend in wavelength dependence of spectral AOD (i.e. in Angstrom Exponent (α440–870, AE) observed in the AERONET data showing a clear increase over the years during the pre-monsoon season (see Fig. 2c). Our analysis reveals that there is a clear decrease in AOD observed during pre-monsoon period over the Northern part of the Indian region and over the North western part of Indian subcontinent due to declining dust emissions This is due to the increased rainfall, which inhibited dust emission and at the Figure 4. The map was generated using MATLAB 2015b, www.mathworks.com
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