Satellite observations of long-term changes in tropical cloud and outgoing longwave radiation from 1985 to 1998

doi:doi:10.1029/2001GL014264

Abstract

Pi-Huan Wang

Science and Technology Corporation, Hampton, Virginia, USA

Patrick Minnis

Atmospheric Sciences Competency, NASA Langley Research Center, Hampton, Virginia, USA

Bruce A. Wielicki

Atmospheric Sciences Competency, NASA Langley Research Center, Hampton, Virginia, USA

Takmeng Wong

Atmospheric Sciences Competency, NASA Langley Research Center, Hampton, Virginia, USA

Lelia B. Vann

Atmospheric Sciences Competency, NASA Langley Research Center, Hampton, Virginia, USA

Cloud vertical distributions and radiation data from satellites taken between 1985 and 1998 were analyzed to determine the impact of clouds on outgoing longwave radiation (OLR) in the Tropics. Clouds with a 1-μm optical depth greater than 0.025 above 12 km decreased, while those below 12 km increased. The OLR mean and decadal trend were 254 Wm⁻² and 3.9 Wm⁻²/decade, respectively. The mean cloud and OLR results were used to derive a value of 0.36 for the tropical mean cloud longwave effective emissivity. Changes in cloud vertical distributions account for 40% of the OLR trend. A change in cloud effective emissivity of −0.026/decade could account for the remainder of the OLR changes. These changes suggest reduced mean cloud opacity, a drier troposphere, and a strengthened large-scale circulation in the Tropics during the period.

Published 23 May 2002.

Citation: Wang, P.-H., P. Minnis, B. A. Wielicki, T. Wong, and L. B. Vann (2002), Satellite observations of long-term changes in tropical cloud and outgoing longwave radiation from 1985 to 1998, Geophys. Res. Lett., 29(10), 1397, doi:10.1029/2001GL014264.

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