An Exploration of Multi Decadal, Continental-Scale Evapotranspiration Inferred from Weather Data

根据天气数据推断的多年代、大陆尺度蒸散量的探索

• 批准号: 1446798
• 负责人: Guido Salvucci
• 金额: $ 33.36万
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-03-01 至 2019-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1446798&HistoricalAwards=false
• 关键词: Exploration; Multi; Decadal; Continental; Scale

An Exploration of Multi Decadal, Continental-Scale EvapotranspirationInferred from Weather DataLand surface evapotranspiration (ET) is the transformation of water in soils, plants and lakes into atmospheric water vapor. It is a significant part of the regional water balance with direct influence on streamflow and groundwater recharge. ET is also a significant part of the atmospheric water balance with direct influence on humidity and rainfall. Because of the energy required to vaporize water, the ET process also influences land and air temperature. Despite its relevance to water resources and climate, ET is notoriously difficult to measure, especially at regional scales. This proposal develops and applies a newly discovered method for estimating ET from readily available weather data, based on daily patterns of relative humidity. With this method, the proposal addresses these questions: * What is the seasonal and geographic variability of ET over the U.S? * What are the seasonal and geographic roles of forcing (temperature, humidity, wind and precipitation) and surface properties (soil, vegetation, topography) in these space-time patterns? * What trends have occurred in ET over the last 50 years, and what is responsible for those trends (for instance, wind, moisture availability, radiation, temperature)?* How do these seasonal, geographical, and decadal variabilities (including trends) compare with state-of-the art climate models; and * How do the interactions between the land surface, the lower atmosphere, and cloud formation influence relative humidity? Broader impacts of this work include development and demonstration of a practical means for water resource managers to estimate ET, better understanding of geographic water resource availability and new observational constraints on climate models. In addition, the work will involve a graduate and undergraduate student, as well as a high school senior.Progress in understanding surface and atmospheric controls on ET, feedbacks between the surface and atmosphere, and decadal time scale variations in ET, require reliable estimates of ET. Direct, continuous measurements, however, are recent (approximately one decade old), and spatially limited (a few hundreds of flux stations, each measuring approximately one square kilometer of land area). Because of this, hydroclimatological research on ET has been either limited in space and time or has relied on model output. The proposed work overcomes these limitations and addresses critical questions related to the space-time variations of ET over decadal time scales (including trends), the drivers of these variations, and the ability of current climate models to capture these variations. Typically estimating ET requires either measurement of soil water status and surface temperature, or temporally integrated modeling of the water and energy balance. For broad use, the former requires remotely sensed observations, and the latter requires calibration of numerous soil hydraulic and vegetation parameters, leading to highly model-formulation dependent results. The method developed here provides ET estimation without site-specific calibration. The parsimony of required forcing and surface data allows for broad geographic and temporal (e.g., prior to the satellite era) application, and yields results that are significantly less model dependent. The intellectual merit of the proposed research is in addressing a vital questions of hydrologic sciences - determination of the terrestrial evaporation component of the water balance at hourly to decadal time scales over continental scales.

基于气象资料的多年代际大陆尺度蒸散量研究地面蒸散量（ET）是指土壤、植物和湖泊中的水分转化为大气水蒸气的过程。 它是区域水平衡的重要组成部分，直接影响径流和地下水补给。 ET也是大气水分平衡的重要组成部分，直接影响湿度和降雨量。 由于蒸发水需要能量，ET过程也会影响陆地和空气温度。 尽管它与水资源和气候相关，但ET是众所周知的难以测量，特别是在区域尺度上。 该建议开发并应用了一种新发现的方法，根据每日相对湿度模式，从现成的天气数据中估计ET。 通过这种方法，该提案解决了这些问题：* 美国ET的季节和地理变化是什么？ * 在这些时空模式中，强迫（温度、湿度、风和降水）和表面特性（土壤、植被、地形）在季节和地理上有什么作用？ * 在过去的50年里，ET发生了什么趋势，是什么导致了这些趋势（例如，风，水分可用性，辐射，温度）？这些季节、地理和年代际变化（包括趋势）如何与最先进的气候模式进行比较;以及 * 陆地表面、低层大气和云形成之间的相互作用如何影响相对湿度？ 这项工作的更广泛的影响包括为水资源管理人员开发和演示一种实用的方法来估计ET，更好地了解地理水资源的可用性和对气候模型的新的观测限制。 此外，这项工作将涉及一个研究生和本科生，以及高中senior.Progress在了解地面和大气控制ET，地面和大气之间的反馈，ET的十年时间尺度变化，需要可靠的估计ET。 然而，直接的、连续的测量是最近的（大约十年前），并且空间有限（几百个通量站，每个测量大约一平方公里的土地面积）。 因此，对蒸散的水文气候学研究要么在空间和时间上受到限制，要么依赖于模式输出。拟议的工作克服了这些局限性，并解决了与ET在十年时间尺度上的时空变化（包括趋势），这些变化的驱动因素以及当前气候模型捕捉这些变化的能力有关的关键问题。通常，估计ET需要测量土壤水分状况和地表温度，或对水分和能量平衡进行时间综合建模。为了广泛使用，前者需要遥感观测，后者需要校准许多土壤水力和植被参数，导致高度依赖模型制定的结果。这里开发的方法提供ET估计没有特定地点的校准。 所需强迫和地表数据的简约性允许广泛的地理和时间（例如，在卫星时代之前）应用，并且产生显著较少依赖于模型的结果。 拟议研究的智力价值在于解决水文科学的一个重要问题--确定大陆尺度上每小时至十年时间尺度的水平衡的陆地蒸发部分。