Changes in the circulation of the North American monsoon using the CMIP5 scenarios
Abstract
We examine the hypothesis that global warming during the 21th century will increase the land-sea thermal contrast (LSTC) and therefore the intensity and initial rainfall of the North American Monsoon (NAM). To test this hypothesis, future changes (2075-2099 minus 1979-2004) in LSTC, moisture flux convergence, and stability in the NAM region are analyzed using six global climate models (GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) under the RCP8.5 radiative scenario. A validation analysis was assessed with several observed rainfall datasets (ERA-Interim, GPCP, CRU) for the 1979-2004 period; ERA-Interim also served to validate the circulation variables of the CMIP5 models. The mean ensemble of the CMIP5 models projects a future surface warming of ~5°C in JJA in the monsoon region and a significant increase in the vertical static stability. The total LSTC in JJA also increases by ~4oC with an early start of the continental warming in June. However, future scenarios show an unexpected delay of the monsoon onset of the rainy season with a significant reduction of precipitation in July, especially in the coastal regions, where stronger divergence than observed is projected. This appears to be associated with changes in the circulation of the North Pacific and Atlantic anticyclones and the Intertropical Convergence Zone. At the end of the summer, an increase of moisture flux convergence produces a significant increase of precipitation in September in the NAM region.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2013
- Bibcode:
- 2013AGUSM.A33D..06C
- Keywords:
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- 1616 GLOBAL CHANGE / Climate variability;
- 3305 ATMOSPHERIC PROCESSES / Climate change and variability;
- 1637 GLOBAL CHANGE / Regional climate change