Larger Increases in More Extreme Local Precipitation Events as Climate Warms

• Published in: Geophysical research letters 2019-06, Vol.46 (12), p.6885-6891
• Main Authors: Li, Chao, Zwiers, Francis, Zhang, Xuebin, Chen, Gang, Lu, Jian, Li, Guilong, Norris, Jesse, Tan, Yaheng, Sun, Ying, Liu, Min
• Format: Article
• Language: English
• Subjects: 21st century; Amplification; Atmospheric circulation; Atmospheric circulation changes; atmospheric dynamics; Atmospheric models; Atmospheric moisture; Climate; climate change; Climate models; Computer simulation; extreme precipitation events; Extreme weather; Greenhouse effect; Greenhouse gases; Hydrologic data; Identification; impact‐relevant spatial scales; Local climates; Local precipitation; Moisture; Precipitation; Precipitation data; Regional climates; Regions
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2019GL082908

Climate models project that extreme precipitation events will intensify in proportion to their intensity during the 21st century at large spatial scales. The identification of the causes of this phenomenon nevertheless remains tenuous. Using a large ensemble of North American regional climate simulations, we show that the more rapid intensification of more extreme events also appears as a robust feature at finer regional scales. The larger increases in more extreme events than in less extreme events are found to be primarily due to atmospheric circulation changes. Thermodynamically induced changes have relatively uniform effects across extreme events and regions. In contrast, circulation changes weaken moderate events over western interior regions of North America and enhance them elsewhere. The weakening effect decreases and even reverses for more extreme events, whereas there is further intensification over other parts of North America, creating an “intense gets intenser” pattern over most of the continent. Plain Language Summary Climate models project that extreme precipitation events will intensify during the 21st century at large spatial scales, with several studies suggesting that the most extreme events will exhibit the highest rate of intensification. Identification of the causes of this phenomenon nevertheless remains tenuous, partly because estimating long‐term changes in precipitation extremes is difficult, particularly for precipitation extremes at impact‐relevant spatial scales. Robustly estimated changes in precipitation extremes at small spatial scales can only be obtained from large extreme precipitation data sets from large ensemble simulations. We employ a large ensemble regional climate simulation experiment performed for North America. The large volume of output from this experiment allows us to confidently obtain statistical evidence that precipitation intensification occurs more rapidly with warming for more extreme events at impact‐relevant spatial scales, and secondly, to determine the causes for this phenomenon. The effect of atmospheric moisture increases caused by greenhouse gas warming is found to be similar for extreme precipitation events of different intensities, ranging from 2‐ to 50‐year events. In contrast, atmospheric circulation change due to greenhouse gas warming tends to reduce the effect of the atmospheric moisture increases on less intense events rather than intensifying the effect on more extreme events. Key Points