Explaining the Surprising Simplicity of Continental Evapotranspiration

解释大陆蒸发量的惊人简单性

• 批准号: 2129576
• 负责人: Kaighin McColl
• 金额: $ 31.08万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-11-15 至 2024-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2129576&HistoricalAwards=false
• 关键词: Explaining; Surprising; Simplicity; Continental; Evapotranspiration

Most of the water that falls to the ground as rain returns to the atmosphere through surface evaporation and through transpiration, the process through which plants take up water in their roots and release it from their leaves. Accurate estimates of evapotranspiration (ET), the sum of evaporation and transpiration, are thus essential for understanding all things related to the water cycle, including water resources, surface climate, the carbon cycle, and the health of crops and ecosystems. ET can be measured directly, but such measurements require sophisticated equipment which is only available at a few sites. Alternative methods exist to estimate ET from standard weather observations but such methods generally need additional information, such as soil moisture and vegetation height, which is less commonly available. They may also involve calibrations which are not based on first principles and can be strongly site specific.Research under this award develops and tests a new ET estimation method based on surface air temperature and moisture, which are available across the full global network of surface weather stations, along with satellite observations of surface net radiation. The new method also eliminates the need for site-specific calibration. The premise of the method is that the land surface and the air above it are in a state of surface flux equilibrium (SFE), meaning that the surface air temperature and humidity have adjusted to the heat and moisture given off by the land, so that observations of air temperature and humidity can be used to infer ET. Earlier work has demonstrated that the method works, but more work is needed to understand the properties of the method and the limits of its applicability. In particular, the project seeks to understand why the SFE method works as well as it does, despite its simplicity, over inland continental areas. On the other hand, the method typically underestimates ET over oceans (where ET is just evaporation) and overestimates it near coastlines, and the project also addresses these issues. The work is conducted using a high-resolution atmospheric model, the System for Atmospheric Modeling (SAM), by comparing ET derived from SFE with the actual ET from the model output.The work has broader impacts due to the societal value of SFE-derived ET estimates. If successful, the new method will vastly expand the availability of ET estimates around the globe, thereby providing a valuable resource for addressing societally important problems related to the water cycle. In addition the Principal Investigator of the project conducts public outreach through the Harvard natural history museum, and the project provide support and training to a graduate student.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

大部分随雨水降落到地面的福尔斯水通过表面蒸发和蒸腾作用返回大气，蒸腾作用是植物在根部吸收水分并从叶子释放水分的过程。因此，准确估计蒸发蒸腾量（ET），即蒸发和蒸腾的总和，对于了解与水循环有关的所有事情，包括水资源，地表气候，碳循环以及作物和生态系统的健康至关重要。 ET可以直接测量，但这种测量需要复杂的设备，这些设备只在少数几个地点可用。 还有其他方法可以从标准天气观测中估计ET，但这些方法通常需要额外的信息，如土壤湿度和植被高度，这些信息不太常见。该奖项下的研究开发和测试了一种新的基于地面空气温度和湿度的ET估计方法，该方法可在整个全球地面气象站网络中使用，沿着地面净辐射的卫星观测。 新方法还消除了现场特定校准的需要。 该方法的前提是，地面及其上方的空气处于表面通量平衡（SFE）状态，这意味着地面空气温度和湿度已经适应了陆地释放的热量和水分，因此可以使用空气温度和湿度的观测来推断ET。 早期的工作已经证明了该方法的工作，但需要更多的工作来了解该方法的属性及其适用性的限制。 特别是，该项目试图了解为什么SFE方法的工作，以及它做的，尽管它的简单，在内陆大陆地区。 另一方面，该方法通常低估了海洋上的ET（ET只是蒸发），高估了海岸线附近的ET，该项目也解决了这些问题。 这项工作是使用一个高分辨率的大气模式，大气模拟系统（SAM），通过比较从超临界流体萃取的ET与实际ET从模式output.The工作有更广泛的影响，由于社会价值的超临界流体萃取的ET估计。如果成功的话，新方法将极大地扩大地球仪的可用性，从而为解决与水循环相关的社会重要问题提供宝贵的资源。此外，该项目的主要研究者通过哈佛自然历史博物馆进行公众宣传，该项目为一名研究生提供支持和培训。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Soil Moisture Control of Precipitation Reevaporation over a Heterogeneous Land Surface

异质地表降水再蒸发的土壤湿度控制

• DOI: 10.1175/jas-d-21-0059.1
• 发表时间: 2021
• 期刊: Journal of the Atmospheric Sciences
• 影响因子: 3.1
• 作者: Cheng, Yu;Chan, Pak Wah;Wei, Xin;Hu, Zeyuan;Kuang, Zhiming;McColl, Kaighin A.
• 通讯作者: McColl, Kaighin A.

Apparent surface conductance sensitivity to vapour pressure deficit in the absence of plants

• DOI: 10.1038/s44221-023-00147-9
• 发表时间: 2023-10
• 期刊: Nature Water
• 作者: L. V. Vargas Zeppetello;K. McColl;Jeremiah A. Bernau;Brenda B. Bowen;Lois I. Tang;N. M. Holbrook;Pierre Gentine;Peter Huybers

Anomalously Darker Land Surfaces Become Wetter Due To Mesoscale Circulations

由于中尺度环流，异常黑暗的陆地表面变得更加湿润

• DOI: 10.1029/2023gl104137
• 发表时间: 2023
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Cheng, Yu;Hu, Zeyuan;McColl, Kaighin A.
• 通讯作者: McColl, Kaighin A.

Thermally Direct Mesoscale Circulations Caused by Land Surface Roughness Anomalies

• DOI: 10.1029/2023gl105150
• 发表时间: 2023-08
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Yu Cheng;K. McColl