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GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L10807, doi:10.1029/2007GL029419, 2007

Latitudinal variation of aerosol optical depths from northern Arabian Sea to Antarctica

V. Vinoj

Center for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore, India


Anjit Anjan

India Meteorological Department, Pune, India


M. Sudhakar

National Centre for Antarctic and Oceanic Research, Goa, India


S. K. Satheesh

Center for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore, India


J. Srinivasan

Center for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore, India


K. Krishna Moorthy

Space Physics Laboratory, Vikram Sarabhai Space Center, Thiruvananthapuram, India


Abstract

Measurements of the spectral aerosol optical depths (AODs) were made over the Arabian Sea, Indian Ocean, Southern Ocean, and Antarctica during a trans-continental cruise experiment conducted during January to April 2006. Our investigations show that AODs (at 500 nm) remain low (≤0.1) and steady in the Southern Indian Ocean (20°S to 40°S). In contrast, large latitudinal gradients exist north of 20°S. The AODs increase nearly exponentially from ∼0.1 near Antarctica to reach a value as high as 0.7 in the northern Arabian Sea (∼15°N). The latitudinal gradients were larger in summer than in winter. The comparison of measured daily optical depths with those retrieved from MODIS satellite sensor showed good agreement (within ∼0.02) for regions north of 40°S. The AODs were higher over remote oceans between 40°S to 60°S (MODIS observations) latitudes as a result of enhanced sea-salt production due to high winds associated with the ‘Roaring Forties.’

Received 20 January 2007; accepted 13 April 2007; published 24 May 2007.

Keywords: aerosols; optical depths; Southern Ocean.

Index Terms: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906); 1610 Global Change: Atmosphere (0315, 0325); 1704 History of Geophysics: Atmospheric sciences.

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Citation: Vinoj, V., A. Anjan, M. Sudhakar, S. K. Satheesh, J. Srinivasan, and K. K. Moorthy (2007), Latitudinal variation of aerosol optical depths from northern Arabian Sea to Antarctica, Geophys. Res. Lett., 34, L10807, doi:10.1029/2007GL029419.