Pre-monsoon aerosol optical properties and spatial distribution over the Arabian Sea during 2006

This paper presents the results of ship cruise and land observations of columnar aerosol characteristics over the Arabian Sea (AS) and at an in-land urban station Pune, in the western part of India, during the pre-monsoon 2006. Aerosol loading is found to decrease significantly from Pune and west coast of India to far away from the Indian west coast over AS. Relative dominance of coarse-mode particles is observed over pristine oceans, while dominance of fine-mode aerosols is noticed under certain occasions. Curvature of multi-spectral AOT variations is also found to be larger over Far AS (FAS) and Mid AS (MAS) regions, where the aerosol loading seems to be very low, compared to that over Coastal AS (CAS) region. Predominance of coarse- and fine-mode aerosols is found over Northern AS (NAS) and Southern AS (SAS) regions, respectively, along the meridional direction of AS. Surface radiative cooling due to aerosols is found to be more intense over CAS and NAS regions. It is shown that the combination of Angstrom exponent (α) and its second order (α′) could delineate aerosol type and loading.