Scientists Study Global Warming’s Impact On Tropical Rainfall
Updatetime：2013-05-15From：
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Global warming is likely to affect the planet’s water cycle, causing changes in rainfall patterns which could have a huge impact on human lives, economies, and the environment. Findings by scientists studying the impact of global warming on tropical rainfall may lead to better projections of seasonal rainfall, important for community preparedness in the face of climate change.
Two possible mechanisms for tropical rainfall changes have been put forward: The first, known as the “warmer-gets-wetter” view, holds that rainfall will increase in regions where sea surface temperatures rise above average. The second, the “wet-gets-wetter” view, predicts increased rainfall in regions that are already rainy, while dry regions get dryer.
To determine which of these views dominates, the scientists from the University of Hawaii at Manoa and the Chinese Academy of Sciences in Beijing used 18 climate models incorporating historical data to simulate the effects of present climate on future rainfall.
Publishing their findings in the journal Nature Geoscience, they found that ocean warming induces upward air movement and increased rainfall near the Equator, where sea surface temperatures peak. Meanwhile, further away from the Equator, a downward movement of cooler air causes drying. This is consistent with the warmer-gets-wetter view.
At the same time, however, the band of increased rain along the Equator causes seasonal rainfall anomalies that follow the wet-gets-wetter pattern. The two mechanisms are thus complementary, and seasonal rainfall changes in tropical regions are best explained by a combined view.
The wet-gets-wetter mechanism contributes more to seasonal rainfall changes, while warmer-gets-wetter has a larger effect on mean annual rainfall. Since wet-gets-wetter is based on current rainfall, which is easier to observe than sea surface temperatures, predictions of seasonal rainfall can be made with better certainty if this mechanism dominates.
According to the authors, Prof. Shang-Ping Xie from the University of Hawaii at Manoa and Prof. Roger Revelle from the University of California at San Diego: “Because our present observations of seasonal rainfall are much more reliable than the future sea surface temperatures, we can trust the models’ projections of seasonal mean rainfall for regional patterns more than their annual mean projections. This is good news for monsoon regions where rainfall by definition is seasonal and limited to a short rainy season. Many highly populated countries under monsoon influences already face water shortages.” (Universtiy of Hawaii)
The article can be found at: Huang et al. (2013) Patterns of the seasonal response of tropical rainfall to global warming.
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