Temperature scaling of rainfall from weather systems

What is it about?

Temperature regulates the amount of water vapour in the atmosphere, and many stakeholders use temperature predictions to predict future flood risks. This study shows rainfall from weather systems may not follow this relationship now or in the future.

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Photo by Matt Ketchum on Unsplash

Photo by Matt Ketchum on Unsplash

Why is it important?

Government agencies, insurers and other stakeholders often rely on the simple relationship between temperature and maximum atmospheric water vapour of 7% increase in water per degree of surface warming. Outside the tropics, weather systems are responsible for most of the received precipitation (snow and rain). Temperature scaling is based on static physical arguments which exclude any motion of the atmosphere, differences in height, or transport of water vapour from remote regions. But weather systems are dynamical systems by their very nature, which means it is not clear whether the static relation of about 7% more rainfall per degree increase in surface temperature holds. The study finds that in many regions, the static relationship is quite accurate, but extreme events and longer-duration events (multiple days) can produce a lot more rainfall than expected. This means planning based on the static 7% per degree warming might underestimate future risks and exposure to flooding.

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