Research press release


Nature Geoscience

Warmer storms bring greater rainfall swings



Ashish SharmaとConrad Waskoは、オーストラリア全体の広範な気候帯にまたがる79か所の気象観測所における嵐発生時の降雨量測定値を集計し、地表近くの気温と比較した。彼らは、気温が上昇したときに起きる嵐の降雨分布は、その発生過程でより不規則となっており、嵐の始まりと終わりの降雨量はより少なく、最大時の降雨量はより大きくなることを見つけた。このような極端な降雨のパターンは、熱帯から乾燥して寒冷な気候まで全ての緯度にわたって見られた。著者たちは統計的解析と流路の水文学的関連性を結び付け、温度が5℃上昇すると、彼らが研究したオーストラリアの気候帯では洪水のピークが5~20%増加する可能性があると見積もっている。

Australian storms that occur at warmer temperatures have more intense highs and weaker lows in rainfall, according to a paper published online this week in Nature Geoscience. If this trend continues with future warming, the risk of flooding due to short-term extreme bursts of rainfall could increase even if the overall amount of precipitation associated with each storm remains the same.

Heavy precipitation events are thought to become more frequent and more intense with rising temperatures. However, changes in the distribution of rainfall over the course of a storm event had not been noted.

Ashish Sharma and Conrad Wasko compiled measurements of precipitation during storms from 79 weather stations across Australia, spanning a broad range of climate zones, and compared them with near-surface temperatures. They found that the storms occurring at warmer temperatures had more uneven distributions of precipitation across the duration of the storm event, with lower rainfall at the beginning and end of the storm, and a more intense peak of precipitation. This pattern of rainfall extremes held across all latitudes - ranging from tropical to arid to cooler climates. Based on their statistical analysis in combination with hydrologic flow routing relationships, the authors estimate that for a 5 °C temperature increase, flood peaks could increase by 5 to 20 % in the Australian climate zones they studied.

doi: 10.1038/ngeo2456


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