Significant characteristics of aerosol optical depth and cloud cover fraction over the South West region of India

Abstract

This research study is focused on to investigate the seasonal, temporal and spatial variations of aerosol optical depths (AODs) over various major cities in South-West region of India and further to understand the impact of aerosols on cloud microphysics. AOD at 550 nm derived from the MODIS sensors have been analyzed in the present study for the ten-year period of 2003–2012. The retrieved satellite data have been used to study the temporal heterogeneity in columnar aerosol characteristics over the eight different places of South West (SW) region of India with a resolution of 1° × 1° grids in magnitude. On yearly basis, high annual mean AOD values (> 0.5) were found at Mumbai (~ 0.53 ± 0.13), Ahmedabad (~ 0.58 ± 0.18) and Kolkata (~ 0.74 ± 0.064) whereas low annual average AOD values (< 0.2) were found at Bengaluru (~ 0.10 ± 0.22). The percentage variation between highest and lowest average annual AOD value was found to be maximum over Ahmedabad (~ 118%) and minimum over Bengaluru (~ 22%) during the study period of 2003–2012. It was also found that the cloud cover fraction increases with AOD (550 nm) at all selected eight places of SW region of India for the whole period of 2003–2012. The maximum positive slope of the trend line for AOD and CF was found to be for Delhi (+ 0.47) and the minimum for Thiruvananthapuram (+ 0.182). It indicates that the significant increase in the correlation between AOD and CF was found to be larger for those regions which have more aerosol particles produced due to industrial and urban domestic activities, etc. A single paired double tailed distribution student’s t-test has also been applied to the Terra AOD values and cloud parameters with a confidence level of 95%.