Assessments of moisture fluxes east of the Andes in South America in a global warming scenario

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Abstract

The HadRM3P regional model from the UK Hadley Centre has been used to assess the moisture flux and the low-level jet (LLJ) east of the Andes in South America over two time periods: the first can be understood as the current climate and covers the period from 1980 to 1989; the second covers the period from 2080 to 2089 under a future global warming climate as projected by the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A2 high-emission scenario. The results are analyzed considering the vertically integrated moisture transport in the lower atmosphere and the moisture flux between the two core areas of South America—the Amazon Basin and the La Plata River Basin. In order to analyze the moisture transport east of the Andes, composites of South American LLJs were built based on the wind speed and vertical wind shear following the modified Bonner criteria 1 used to define LLJs. Integrations along the lateral boundaries of the two basins show that there could be a more intense moisture transport from tropical regions available to feed the mesoscale convective systems in the subtropical La Plata Basin in the IPCC A2 scenario, as compared to the present. This is because of the intense flow to the south associated with a faster LLJ bringing more moisture from the Amazon Basin southwards. It was also observed that the presence of the LLJ affects moisture convergence in the Amazon Basin in the current climate as well as in the warmer climate. In the future high-emission scenario A2, a more intense LLJ in a global warming climate suggests increased moisture transport from north to south east of the Andes as compared to the present. Copyright © 2008 Royal Meteorological Society

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