The Fast and Slow Response of the Hydrological Cycle

水文循环的快响应和慢响应

• 批准号: 1753656
• 负责人: Brian Soden
• 金额: $ 53.92万
• 依托单位: University of Miami
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-04-01 至 2022-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1753656&HistoricalAwards=false
• 关键词: Fast; Slow; Response; Hydrological; Cycle

The hydrological cycle, besides being responsible for the formation of clouds and producing rainfall, is a key component of the atmospheric energy cycle that links surface cooling via evaporation to atmospheric heating via latent heating release in the atmosphere. Changes in atmospheric water vapor and clouds due to changes in the hydrological cycle also alter the surface-atmosphere exchanges via changes in absorption and reflection of the incoming solar energy and in emission of infrared radiation. Changes in the amount of rainfall and the frequency of heavy rain events have been observed over the last century. These changes are, in part, a result of human emission of greenhouse gases. Increasing levels of carbon dioxide, aerosols, and other greenhouse gases causes warming of the surface and atmosphere, which in turns leads to more evaporation from (ocean) surfaces and increases of the amount of moisture and clouds in the atmosphere, as well as more rainfall. The extra heat transferred away from the surface associated with the strengthening of hydrological cycle warms the atmosphere further. This together with the stronger greenhouse effect due to more moisture in the atmosphere leads to a stronger emission of infrared radiation to the surface, which compensates the surface warming reduction due to stronger evaporation. These changes can occur on both slow (years to decades) and fast (days to months) timescales. It is these changes in the flow of energy, not the increase in moisture, that causes rainfall to increase globally in response to increasing greenhouse gases. Thus, in order to fully understand and predict future changes in rainfall requires a better understanding how the transfer of energy between the surface and atmosphere will change in a warmer climate. This research uses an innovative method of computing the effects of an increase in greenhouse gases and aerosols, and a warmer and more humid climate, on the flow of energy between the surface and atmosphere. Through this new method, termed radiative kernels, the individual contributions of different processes can be isolated and their contributions to the changes in precipitation quantified. In doing so, this research will provide a better understanding of the physical mechanisms that underlie model projections of future precipitation change. In particular, this research strives to better understand the cause of disparities between different model projections of rainfall change and use this information to improve models and ultimately provide more reliable projections of future changes.Because of the role of rainfall in determining the availability of fresh water and agricultural food production, changes in its amount, distribution or intensity have significant impacts on people and the environment. In addition, changes in the occurrence of heavy rainfall events alters the frequency of floods, which cause damage to infrastructure, loss of property, and loss of life. Predicting future changes in rainfall that stem from changes in climate therefore represents a key scientific challenge with important societal benefits. The knowledge gained from this research will ultimately lead to both a better understanding of the underlying physical processes that govern rainfall change and improved predictions of future rainfall change. By increasing the reliability of long term projections of changes in rainfall, this project will help decision makers plan for adequate adaptation and mitigation strategies that, in turn, lessen the cost and consequences of future changes in climate.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.

水文循环除了负责云层的形成和降雨的产生外，还是大气能量循环的关键组成部分，它通过蒸发将地表冷却与通过大气中潜热释放的大气加热联系起来。由于水循环的变化而引起的大气水汽和云的变化也通过改变入射太阳能的吸收和反射以及红外辐射的发射而改变了地表与大气的交换。在上个世纪观测到降雨量和暴雨事件频率的变化。这些变化在一定程度上是人类排放温室气体的结果。二氧化碳、气溶胶和其他温室气体含量的增加导致地表和大气变暖，这反过来又导致（海洋）表面蒸发更多，大气中水分和云的数量增加，以及降雨增加。随着水循环的加强，从地表转移出去的额外热量进一步使大气变暖。再加上由于大气中水分增加而产生的更强的温室效应，导致向地表发射更强的红外辐射，从而补偿了由于更强的蒸发而导致的地表变暖减少。这些变化可以发生在缓慢的（几年到几十年）和快速的（几天到几个月）时间尺度上。正是这些能量流动的变化，而不是水分的增加，导致全球降雨量增加，以应对温室气体的增加。因此，为了充分了解和预测未来降雨的变化，需要更好地了解在气候变暖的情况下，地表和大气之间的能量转移将如何变化。这项研究使用了一种创新的方法来计算温室气体和气溶胶的增加以及更温暖、更潮湿的气候对地表和大气之间能量流动的影响。通过这种称为辐射核的新方法，可以分离出不同过程的个别贡献，并量化它们对降水变化的贡献。这样，这项研究将更好地理解未来降水变化模式预估的物理机制。特别是，本研究力求更好地了解不同模式对降雨变化预估之间差异的原因，并利用这些信息改进模式，最终提供更可靠的未来变化预估。由于降雨在决定淡水供应和农业粮食生产方面的作用，其数量、分布或强度的变化对人类和环境产生重大影响。此外，强降雨事件发生的变化改变了洪水发生的频率，从而造成基础设施的破坏、财产的损失和生命的损失。因此，预测由气候变化引起的未来降雨变化是一项具有重要社会效益的关键科学挑战。从这项研究中获得的知识最终将使我们更好地理解控制降雨变化的潜在物理过程，并改进对未来降雨变化的预测。通过提高对降雨变化的长期预测的可靠性，该项目将有助于决策者制定适当的适应和缓解战略，从而减少未来气候变化的成本和后果。该奖项反映了美国国家科学基金会的法定使命，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。