Role of fine mode aerosols in modulating cloud properties over industrial locations in north India

Abstract. The influence of aerosols on cloud properties over North India which includes the Indo-Gangetic Plain has been investigated for the years 2000 to 2010. During the years 2004, 2009 and 2010 there has been an abrupt increase in fine mode aerosol optical depth (AOD) inducing a sharp decline in cloud effective radius (CER) in the month of January. The following monsoon during these years was a failure in the region considered for the study. In the year 2010, a highest AOD value of 0.35 was recorded in the month of January. In accordance with the aerosol indirect effect, this large increase in AOD resulted in a significant reduction in CER. The monsoon season in that year was deficient in the study region even though the rest of the country received above normal rainfall. For the years when CER diminished below 12 microns in the month of May, a delay in the advancement of monsoon towards North India is noted even after a normal or early onset in southern peninsula. Meanwhile, a rapid progression took place when it was 12 microns or above. During non-monsoon months an inverse relationship existed between cloud effective radius and liquid water path and a strong positive association occurred in the monsoon months. Present analysis suggests that the excessive aerosol loading and the associated aerosol indirect effects in the months prior to the monsoon season has an effect on the propagation and onset of the south west monsoon over the region.