Heavy Precipitation over Western North America: Synoptic/Mesoscale Forcing and Decadal Trends

暴雨导致的洪水和边坡失稳是北美西海岸最严重的天气相关威胁。 1980年至2008年，加州、俄勒冈州和华盛顿发生了四次洪水灾害，造成的损失超过110亿美元。 洪水和边坡失稳与强降水产生了大部分的总统灾害声明在俄勒冈州和华盛顿，近四分之一的这样的声明在加州。智力的优点：虽然已经学到了很多关于西海岸强降水事件的性质，在过去的十年中，主要的科学问题仍然是悬而未决的关于他们的前因，区域和大规模的气象环境，必要的条件，以及在频率或强度的趋势。这些相互关联的问题将在本次调查中予以考虑。 该项目的具体目标包括：（1）确定从北方加州到加拿大边界地区强降水事件的气候学及其时间和空间特征，（2）确定与这种事件有关的大尺度和区域条件，（3）确定主要降水事件期间的输入流特征，（4）评估西海岸强降水的高分辨率预报的真实性，并确定哪种模式物理产生最准确的模拟，（5）通过诊断高分辨率模拟来确定与这些事件相关的详细大气演变，（6）建立过去60年强降水事件的历史趋势，（7）利用全球气候模式强迫的高分辨率区域模拟来确定该地区下世纪强降水的未来趋势。该项目的智力价值在于它对西海岸强降水事件的特征进行了独特、全面和协同的研究，包括它们的气候学、与它们开始有关的条件、相关的大尺度和区域尺度气象结构、模式正确模拟这些事件的能力、强降水频率的过去趋势以及基于气候模式输出的未来趋势。更广泛的影响：本项目调查的科学问题影响到气象和水文界对即将发生的强降水事件提供及时和准确警报的能力。 该研究还通过为基础设施和区域规划提供必要的信息来造福社会。 另一个与社会重要性相关的问题涉及西海岸强降水的过去趋势以及这些趋势在人为全球变暖下将如何变化。 最后，这项研究应导致在其他地区的地球仪的价值的信息，在那里大量的中纬度地形降水是显着的。

Flooding and slope failures due to heavy precipitation are the most serious weather-related threats for the west coast of North America. Between 1980 and 2008, four flooding disasters in California, Oregon, and Washington caused losses of more than eleven billion dollars. Flooding and slope failures associated with heavy precipitation have produced a majority of presidential disaster declarations in Oregon and Washington, and nearly a quarter of such declarations in California.Intellectual merit:Although a great deal has been learned during the last decade about the nature of West Coast heavy precipitation events, major scientific questions are still outstanding regarding their antecedents, regional and large-scale meteorological environments, necessary conditions, and trends in frequency or intensity. These interrelated questions will be considered in this investigation. The specific objectives of the project include: (1) determining the climatology of heavy precipitation events for the region from northern California to the Canadian border, as well as their temporal and spatial characteristics, (2) identifying the large-scale and regional conditions associated with such events, (3) determining the characteristics of the incoming flow during major precipitation events, (4) evaluating the realism of high-resolution forecasts of heavy West Coast precipitation and determining which model physics produces the most accurate simulations, (5) determining the detailed atmospheric evolutions associated with these events by diagnosing the high-resolution simulations, (6) establishing the historical trends of heavy precipitation events over the past 60 years, and (7) determining the future trends of heavy precipitation over the region for the next century by using high-resolution regional simulations forced by global climate models.The intellectual merit of the project lies in its unique, comprehensive, and synergistic examination of the characteristics of West Coast heavy precipitation events, ranging from their climatology, the conditions associated with their initiation, associated large and regional scale meteorological structures, the ability of models to properly simulate these events, past trends in heavy precipitation frequency, and future trends based on climate model output. The work will resolve a number of major scientific questions about this important meteorological phenomenon.Broader impacts: The scientific issues investigated in this project impact the ability of the meteorological and hydrological communities to provide timely and accurate warnings of upcoming heavy precipitation events. The research also benefits society by providing necessary information for infrastructure and regional planning. Another issue relevant to societal importance deals with past trends in West Coast heavy precipitation and how these trends will change under anthropogenic global warming. Finally, this research should lead to information of value in other parts of the globe where heavy midlatitude orographic precipitation is significant.