Aerosol size distribution over the Arabian Sea during ARMEX-II

A 14-stage Anderson Low Pressure Impactor (LPI) and 4-stage Optical Particle Counter (OPC) were operated in the pre-monsoon ARMEX-II cruise to study the aerosol size distribution (ASD) over the Arabian Sea. These size distributions are compared with the prevailed ASD at Trivandrum. A fairly good agreement is observed between the number size distribution derived from LPI measured mass size distribution and those measured using the OPC. These observed size distributions in the oceanic environments are relatively flatter (with a lower value for the size index) than those obtained over the continental site Trivandrum. The sub-micron mode in ASD is less pronounced in the oceanic environment. Low value of size index in the oceanic environment is an indicator of the dominance of larger size particles.