Diurnal Modulation of Moist Processes in Summertime Droughts and Floods over the Central United States

美国中部夏季干旱和洪水中潮湿过程的日间调节

• 批准号: 9909650
• 负责人: Raymond Arritt
• 金额: $ 21.57万
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-12-01 至 2003-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9909650&HistoricalAwards=false
• 关键词: Diurnal; Modulation; Moist; Processes; Summertime

This team of investigators will evaluate both the relative and combined effects of various processes contributing to summer rainfall and its diurnal variability in the central United States. Diurnal variation has important effects on the summer hydrologic cycle in the mid-latitudes with the nocturnal low-level jet and mesoscale convective systems playing significant roles. Three hypotheses will be examined: (1) The large-scale diurnal variation changes from year to year such that rainfall-inducing processes peak during the nighttime (daytime) in flood (drought) years. (2) During flood years, the contributing processes phase together to produce enhanced precipitation and a stronger nocturnal maximum, while in drought years the components are out of diurnal phase. (3) Large-scale forcing in flood years favors organization and upscale growth of convection, which shifts peak precipitation to late night/early morning. The principal investigators will employ both observational analysis and numerical modeling approaches to examine the hypotheses. The numerical studies will be used to isolate and filter perturbations in both the spatial and temporal domains so that their influences can be systematically examined in regional climate simulations. The study will cover a selection of normal, drought, and flood years in the Midwest. This research is supported as part of NSF's Water and Energy: Atmospheric, Vegetative, and Earth Interactions (WEAVE) effort.

这组调查人员将评估导致美国中部夏季降雨量及其日变化的各种过程的相对和综合影响。日变化对中纬度夏季水循环有重要影响，其中夜间低空急流和中尺度对流系统起着重要作用。将检验三个假说：(1)大尺度的日变化年际变化，使得降雨过程在丰(旱)年的夜间(白天)达到高峰。(2)在丰水年，各贡献过程共同产生降水增强和较强的夜间最大值，而在干旱年，这两个分量都不是昼夜位相。(3)汛期的大尺度强迫有利于对流的组织和高尺度发展，使降水高峰移至深夜/清晨。主要研究人员将使用观测分析和数值模拟方法来检验假设。数值研究将被用来隔离和过滤空间和时间域的扰动，以便在区域气候模拟中系统地检查它们的影响。这项研究将涵盖中西部一些正常、干旱和洪涝的年份。这项研究是美国国家科学基金会水与能源：大气、植物和地球相互作用(Weave)努力的一部分。