Seeking to understand how rising temperatures influence precipitation, scientists at Kyoto University examined how climate change affects extreme rainfall across Japan. Their work focused on the link between warming and atmospheric conditions that drive heavy precipitation.
"We know that the saturation of water vapor increases with temperature at a rate of about 7% per degree Celsius, but not all that water vapor is converted to rainfall, so we weren't sure this temperature scaling applies to the rainfall amount," said first author Sridhara Nayak.
Using data from climate models developed by the Japan Meteorological Agency's Meteorological Research Institute, the researchers analyzed rainfall intensity and atmospheric patterns across seven regions of Japan. They compared current conditions with projections for a 4 C global temperature increase.
The team found that extreme precipitation will intensify by roughly 7% for every degree of warming, confirming that higher temperatures do lead to stronger rainfall. However, the link depends on atmospheric humidity. When the atmosphere is too dry - such as during the hottest days - rainfall weakens. The most extreme precipitation events occur instead during days with the second-highest temperature range, when atmospheric moisture is abundant.
"With this in mind, we need to be prepared for the severe impacts of heavy rainfall in the future by creating a plan for climate change adaptation," said project leader Tetsuya Takemi.
The researchers emphasize that future studies should use higher-resolution data to better capture the cloud systems that generate extreme precipitation, since the current model's 20 km resolution cannot fully resolve such details.
Research Report:Regional and vertical scaling of water vapor with temperature over Japan during extreme precipitation in a changing climate
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