Changes in the Seasonality of Tropical Precipitation in Response to Greenhouse Gases: Local and Remote Forcings
Abstract
When forced with increasing greenhouse gases, all of the CMIP3 models project a delay of the annual cycle of global precipitation and SST. This global phase shift has important regional manifestations, that are quite robust across the CMIP3 ensemble. At regional scales, though, rainfall and temperature anomalies may be more complex than a simple shift and, in places, are better characterized as a change in the shape of the annual cycle. For example, the rainy season in the Sahel is projected not only to start later, but also to be shorter. We explore local and remote sources of the projected seasonal changes in tropical precipitation. First, we show that changes in emissivity and local processes can force a delay, but the effect is too small to explain the coupled model results. Next we investigate the role of changes in sea ice cover in forcing anomalies in the seasonal evolution of extra-tropical surface temperature and the role of atmospheric circulation in communicating the high-latitude signal to the low-latitude ocean and, through SST changes, to tropical precipitation.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.A11G..03B
- Keywords:
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- 1616 GLOBAL CHANGE / Climate variability;
- 1620 GLOBAL CHANGE / Climate dynamics;
- 1637 GLOBAL CHANGE / Regional climate change