Lidar Measurements of Sub-visible Aerosol Layers in the Free Troposphere at a Tropical Coastal Station, Trivandrum, India

摘要

Lidar observations had been conducted to study the long-range transport of aerosol and their effect at tropical station, Trivandrum during the period of 2001-2003. The presence of aerosol layers was observed on many days below about 5 km during the above period. The monthly values of aerosol extinction coefficient profile showed the presence of aerosol layer in the height region up to about 5 km during the summer monsoon periods. However, during the Asian winter monsoon period the aerosol layers were observed in the altitude region between 0.6 and 3 km. The extinction values were high in the winter season and were typically found to be 3.4x10-4 m-1. The aerosol optical depth was calculated by integrating the extinction values in the aerosol layer region and it was found to be between 0.2 and 0.35. The plausible reasons for the formation of these layers were explained using the wind circulation pattern and air back trajectories.