Understanding the Decrease of Precipitation Extremes at High Temperature and its Implications

了解高温下极端降水量的减少及其影响

• 批准号: 1659953
• 负责人: Guiling Wang
• 金额: $ 54.29万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-06-01 至 2023-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1659953&HistoricalAwards=false
• 关键词: Understanding; Decrease; Precipitation; Extremes; Temperature

Recent decades have seen an increasing trend in extreme precipitation intensity (EPI) over much of the globe including the continental US. The trend is generally regarded as a consequence of increasing temperature, as for the same relative humidity warmer air holds more precipitable water than colder air. Apart from the trend, EPI shows similar variation during weather-related temperature fluctuations between warm and cold days, as extreme precipitation events on colder days tend to be less intense than their counterparts on warmer days. But in day-to-day temperature fluctuations the increase of EPI with temperature only holds up to a point, beyond which intensity falls off with further increases in temperature. It is thus of interest to understand why EPI increases with temperature up to a threshold value and then decreases in day-to-day variability, what determines the temperature at which EPI peaks, and how the EPI-temperature relationship changes as a result of long-term increases in temperature.The PI hypothesizes that the reduction in EPI at the highest temperatures is a consequence of the effect of temperature on the moisture difference between air in convective clouds and the ambient air surrounding them. Rising air in convective clouds is generally saturated with water vapor while ambient air surrounding the clouds is not, thus the vigor of clouds is suppressed when drier ambient air is mixed into them. The suppressing effect of ambient air mixed into clouds increases with temperature if the moisture difference between cloud and ambient air increases with temperature, an increase which is expected under reasonable assumptions including a minimal change in ambient relative humidity. Work under this award examines the role of this moisture deficit mechanism in suppressing the development of deep convective clouds from shallow clouds, thereby reducing extreme precipitation at high temperatures. The work also considers the change in the EPI-temperature relationship that occurs as climate warms, with the hypothesis that the relationship remains qualitatively the same but the threshold value shifts to progressively higher temperatures. Additional work considers the possible implications of the moisture deficit mechanism for drought. The work is carried out through a combination of observational analysis and climate model simulations.The project has broader impacts due to the severe consequences of extreme precipitation for human activities and the need to understand how the threats posed by extreme precipitation will evolve in a changing climate. The PI is also engaged in a variety of outreach activities at local schools, including a 5-day workshop for middle- and high-school math and science teachers. In addition, the project supports a graduate student and a postdoctoral researcher, thereby providing for the development of the workforce in this research area.

近几十年来，包括美国大陆在内的全球大部分地区的极端降水强度(EPI)呈上升趋势。这一趋势通常被认为是温度上升的结果，因为在相同的相对湿度下，温暖的空气比寒冷的空气含有更多的可沉淀水分。除了这一趋势外，EPI在暖天和冷天之间与天气有关的温度波动中也显示出类似的变化，因为在较冷的日子发生的极端降水事件往往没有温暖天的极端降水事件那么强烈。但在逐日的温度波动中，EPI随温度的增加只维持到一个点，超过这个点后，强度会随着温度的进一步上升而减弱。因此，人们很有兴趣了解为什么EPI随着温度增加到一个阈值，然后逐日变率减少，是什么决定了EPI达到峰值的温度，以及EPI-温度关系是如何随着温度的长期升高而变化的。PI假设，最高温度下EPI的减少是温度对对流云中的空气和周围环境空气之间湿度差的影响的结果。对流云中上升的空气通常被水蒸气饱和，而云周围的环境空气不饱和，因此当更干燥的环境空气混合到云中时，云的活力被抑制。如果云和环境空气之间的湿度差随温度增加，则混合到云中的环境空气的抑制效果随温度增加，在包括环境相对湿度最小变化在内的合理假设下，这种增加是预期的。该奖项的工作考察了这种水分亏缺机制在抑制浅层云的深层对流云发展方面的作用，从而减少了高温下的极端降水。这项工作还考虑了随着气候变暖而发生的EPI-温度关系的变化，假设这种关系在性质上保持不变，但阈值向逐渐升高的温度移动。其他工作考虑了水分亏缺机制对干旱的可能影响。这项工作是通过观测分析和气候模型模拟相结合的方式进行的。由于极端降水对人类活动的严重后果，以及需要了解极端降水构成的威胁将如何在不断变化的气候中演变，该项目具有更广泛的影响。PI还在当地学校开展了各种外展活动，包括为初中和高中数学和科学教师举办的为期5天的讲习班。此外，该项目还支持一名研究生和一名博士后研究员，从而为这一研究领域的劳动力发展提供支持。

项目成果

Eco-hydrological responses to recent droughts in tropical South America

• DOI: 10.1088/1748-9326/ac507a
• 发表时间: 2022-02-01
• 期刊: ENVIRONMENTAL RESEARCH LETTERS
• 影响因子: 6.7
• 作者: Jiang, Yelin;Yang, Meijian;Wang, Guiling
• 通讯作者: Wang, Guiling

Modeled Response of South American Climate to Three Decades of Deforestation

南美气候对三个十年森林砍伐的模拟响应

• DOI: 10.1175/jcli-d-20-0380.1
• 发表时间: 2021
• 期刊: Journal of Climate
• 影响因子: 4.9
• 作者: Jiang, Yelin;Wang, Guiling;Liu, Weiguang;Erfanian, Amir;Peng, Qing;Fu, Rong
• 通讯作者: Fu, Rong

The peak structure and future changes of the relationships between extreme precipitation and temperature

极端降水与气温关系的峰值结构及未来变化

• DOI: 10.1038/nclimate3239
• 发表时间: 2017-04-01
• 期刊: NATURE CLIMATE CHANGE
• 影响因子: 30.7
• 作者: Wang, Guiling;Wang, Dagang;Parr, Dana T.
• 通讯作者: Parr, Dana T.

Causes for the Negative Scaling of Extreme Precipitation at High Temperatures

高温极端降水负缩放的原因

• DOI: 10.1175/jcli-d-22-0142.1
• 发表时间: 2022
• 期刊: Journal of Climate
• 影响因子: 4.9
• 作者: Sun, Xiaoming;Wang, Guiling
• 通讯作者: Wang, Guiling

Monotonic Increase of Extreme Precipitation Intensity With Temperature When Controlled for Saturation Deficit

• DOI: 10.1029/2022gl097881
• 发表时间: 2022-03
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Guiling Wang;Xiaoming Sun