The aerosol and radiometric data collected at Kaashidhoo Climate Observatory (4.9 N, 73.5 E) from February 1998 to April 1999 during the Indian Ocean Experiment (INDOEX) have been analyzed to document the short-wave and long-wave aerosol radiative forcing as a function of seasonal variations in aerosol chemical and micro- physical properties. The rotated principal component analysis of chemical and micro- physical data revealed three distinctive modes of variability linked to sea salt, dust and anthropogenic aerosol (sulfates, ammonium, nitrates, organics and soot), respectively. The anthropogenic mode represented species transported from the Indian subcontinent and was prevalent during winter monsoon, whereas mineral dust transported from the Arabian Peninsula and locally produced sea salt were dominant modes during summer monsoon. The seasonal variations of Angstrom parameter derived from CIMEL data at Kaashidhoo were strongly correlated with aerosol modes, confirming the prevalence of large particles during the summer. To quantify the aerosol forcing over the North- ern Indian Ocean, we developed a three-mode aerosol optical model and calculated daily short-wave and long-wave forcing at the top of the atmosphere, surface and in the atmosphere using CIMEL observations of aerosol optical thickness as input.
EGS General Assembly Conference Abstracts
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