Tropical rainfall trends from GPCP analyses

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https://orcid.org/0000-0002-7812-851X

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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Abstract

The monthly and pentad GPCP-precipitation data from 1979 to present are analyzed to obtain trends in the tropical hydrological cycle over the last three decades. Results show that tropical precipitation has intensified in the rising regions of the Walker and Hadley circulations while the relatively dry subsidence regions have become drier. In addition, the precipitation PDF has shown distinct signatures for the tropical oceans and land. The tropical oceans present an artificial shift in PDF toward more heavy rainfall around 1987 due to the inclusion of SSM/I data in the merged product. The tropical land does not show significant shift in PDF due to the contribution of many gauge observations. Trend analysis of the top 10% heavy rainfall in the pentad data shows that tropical oceans present an overall positive trend of 1.17 mm/day/decade for the last three decades after removing the artificial jump in the pre-SSM/I data. Precipitation from tropical land shows large decadal variation and presents a smaller positive trend of 0.68 mm/day/decade. The Tropics as a whole displays a positive trend of 1.03 mm/day/decade in the top 10% heavy rainfall.