Linkage of aerosol optical depth with rainfall and circulation parameters over the Eastern Gangetic Plains of India

Abstract

The aerosol optical depth (AOD) is an important physical parameter and dimensionless number. The possible link between AOD and variability of summer monsoon rainfall and surface temperature over the densely populated Gangetic Plain may be used to assess change in weather and climate over the Plain. For examining the impact of AOD on summer monsoon rainfall and surface temperature, monthly data of AOD for the period of 2000-2015 are obtained from a remotely sensed moderate resolution imaging spectro-radiometer sensor at 550 nm and at a surface resolution of 1 • × 1 •. For the period of 2000-2015, rainfall and surface temperature data at a resolution of 1 • × 1 • are obtained from Indian Meteorological Department (IMD) and surface wind data are obtained from National Centers for Environmental Prediction (NCEP). Summer monsoon rainfall and AOD are inversely related during 2000-2015. On an average, a difference in the mean monthly surface maximum and minimum temperatures increases (decreases) with a decrease (increase) of AOD. The high degree of correlation exists between AOD and a difference in T max and T min during January to June-July. In winter months, relative strength of negative vorticity over the Gangetic Plain and positive vorticity in the adjacent area may be cause of more dispersion of AOD in February in comparison with that in December and January and therefore more AOD is noticed in January and December.

Large-Scale Urban Heating and Pollution Domes over the Indian Subcontinent

“…5). However, in biosphere reserves in This denotes that as AOD levels increase, LST levels tend to decrease, possibly due to the solar dimming effect, as the thick layer of aerosol acts as a barrier to incoming solar radiation and can reduce surface insolation, resulting in a lower surface temperature [23,45,60]. Sen Roy [15] also observed in a study on the Indo-Gangetic plain that AOD was generally negatively related to temperature to some extent over the urban domain.…”

“…An understanding of the relationship between AOD and LST was also sought in different geophysical environments across the Indian subcontinent. Worldwide, several studies show a negative relationship between LST and AOD, while some show a positive one [20][21][22][23][24][25][26]. Increasing AOD levels affect the earth's energy budget by scattering and absorbing insolation.…”

“…Increasing AOD levels affect the earth's energy budget by scattering and absorbing insolation. As a result, the land surface may be cooled [23]. Based on a study conducted in Delhi in 2007 and 2008, high levels of AOD tend to have lower surface temperatures during daytime [20].…”