this work has been supported by the grant from department of science and technology, government of india under the DST-PURSE programme ( No.SR/S9/z-23/2010/15)and "studies on Aerosol Environment at Kolkata Located Near the Land-Ocean Boundary as a part of ARFI network under ISRO-GBP" , being carried out at Institute of Radio physics and Electronics, University of Calcutta.The authors acknowledge with thanks the West Bengal Pollution Control Board (WBPCB), Kolkata for providing us continuous ambient air quality data for our analysis.