Temporal heterogeneity in aerosol characteristics at a tropical coastal station and the resulting radiative impacts

Abstract

In this paper, we report the results of extensive, and all-season, collocated, measurements of several aerosol parameters [such as spectral aerosol optical depth (AOD) at 10 bands spanning from UV to IR; mass size distribution and mass concentration of composite aerosols; as well as mass concentration and mass mixing ratio of aerosol black carbon (BC)] for over a 4-year period (January 2000 to December 2003), from an unindustrialized coastal location, Trivandrum (8.55°N, 76.9°E), close to the southern tip of Indian peninsula and use these properties to estimate the aerosol short wave radiative forcing. The results show that the top of the atmosphere (TOA) forcing is significantly positive during winter while it changes to negative during monsoon and post monsoon seasons. The surface forcing decreases from winter to summer. Consequently, the net atmospheric absorption decreases from a high value in winter to low values during monsoon.