Understanding the Effects of Land Hydrology, Water Volatility, and Rotation Rate on Clouds, Climate, and Circulation in a Hierarchy of Models

了解模型层次结构中陆地水文、水波动和自转速率对云、气候和环流的影响

• 批准号: 2310364
• 负责人: Jonathan Mitchell
• 金额: $ 65.45万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-01 至 2026-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2310364&HistoricalAwards=false
• 关键词: Understanding; Effects; Land; Hydrology; Water

Any first-principles theory of the climate dynamics of the Earth should apply across a broader range of conditions than those found on Earth. Such a theory should predict, for example, how the jet streams would change if the planetary rotation rate were faster or slower, or how clouds and precipitation would change if water were more or less abundant. But such Earth analogs are not readily available to test our theories and help us gain confidence in our understanding of the Earth. Work performed under this award explores the idea that Titan, despite being a moon of Saturn with a surface temperature of -290F, can serve as a useful Earth analog. The analogy is based on observations from the Cassini mission showing that Titan has all the features of an Earth-like hydrological cycle: clouds, rain (often torrential rain from large storms), and surface evaporation from lakes and seas, only with methane instead of water. The Principal Investigator (PI) of this award has developed a "water volatility" parameter that allows methane at Titan-like temperatures to be treated as a kind of water equivalent in simulations of Earth's atmosphere. With this treatment Earth and Titan can be treated as climate systems that fall along a continuum, so that a Titan-like hydrological cycle can be produced from Earth's hydrological cycle by increasing the value of the volatility parameter from one to about three. Two other parameters that must also be changed to produce a Titan-like climate state are the planetary rotation rate, as a day on Titan lasts 16 Earth days, and the amount and distribution of land area, as the tropical latitudes of Titan are entirely land covered. The project tests the extent to which these three parameters suffice to account for the essential differences between Earth-like and Titan-like climates.One issue addressed here is the behavior of low and high clouds under changing water volatility, as previous work by the PI (see AGS-1912673) shows that low clouds tend to descend while high clouds ascend under increasing volatility. The two layers merged at low volatility and are abruptly replaced by a single very thick layer at high volatility. This behavior, which was produced in a single-column atmospheric model, is further explored using a general circulation model and a global storm-resolving model (the ICON model from the Max Planck Institute for Meteorology). Additional work considers changes in atmospheric circulation as parameters are varied from Earth-like to Titan-like. One consideration is that the tropical land cover on Titan causes the bulk of surface evaporation to occur at higher latitudes than on Earth and another is that the slower rotation rate causes different types and sizes of atmospheric wave motions to occur on Titan.Broader impacts of the project include a number of educational activities, one of which is a research cruise on Santa Monica Bay during which students collect data related to the temperature and circulation of the bay. Another is the development and construction of a laboratory device to demonstrate density-driven overturning circulations relevant to oceans and planetary atmospheres. The award also provides support and training for a graduate student, thereby promoting workforce development in this research area.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.

任何地球气候动力学的第一原理理论都应该适用于比地球上发现的更广泛的条件。例如，这样的理论应该预测，如果行星自转速度更快或更慢，急流将如何变化，或者如果水丰度或多或少，云和降水将如何变化。 但这样的地球类比并不容易用来检验我们的理论并帮助我们对地球的理解获得信心。 该奖项下进行的工作探索了这样一个想法：泰坦虽然是土星的卫星，表面温度为 -290°F，但可以作为有用的地球模拟。 这个类比是基于卡西尼号任务的观测结果，显示土卫六具有类地水文循环的所有特征：云、雨（通常是大风暴带来的倾盆大雨）以及湖泊和海洋的表面蒸发，只不过是甲烷而不是水。水。 该奖项的首席研究员（PI）开发了一种“水挥发性”参数，可以在模拟地球大气层时将类土卫六温度下的甲烷视为一种水等价物。 通过这种处理，地球和土卫六可以被视为沿着连续体的气候系统，因此通过将波动性参数的值从 1 增加到大约 3，可以从地球的水文循环中产生类似土卫六的水文循环。 为了产生类似土卫六的气候状态，还必须更改另外两个参数：行星自转速度（土卫六上的一天持续 16 个地球日）以及陆地面积的数量和分布（因为土卫六的热带纬度完全是陆地）覆盖。 该项目测试了这三个参数在多大程度上足以解释类地气候和类泰坦气候之间的本质差异。这里解决的一个问题是低云和高云在水波动变化下的行为，正如项目负责人之前的工作一样（参见 AGS-1912673）表明，在波动性增加的情况下，低云倾向于下降，而高云则上升。 这两层在低挥发性时合并，并在高挥发性时突然被一个非常厚的层所取代。 这种在单柱大气模型中产生的行为可以使用大气环流模型和全球风暴解析模型（马克斯·普朗克气象研究所的 ICON 模型）进行进一步探索。 其他工作考虑了大气环流的变化，因为参数从类地到类土卫六变化。 一个考虑因素是土卫六上的热带土地覆盖导致大部分表面蒸发发生在比地球更高的纬度上，另一个考虑因素是较慢的旋转速度导致土卫六上发生不同类型和大小的大气波动。该项目包括许多教育活动，其中之一是圣莫尼卡湾的研究巡游，学生们在此期间收集与海湾温度和环流相关的数据。 另一个是开发和建造一个实验室装置，以演示与海洋和行星大气相关的密度驱动的翻转环流。 该奖项还为研究生提供支持和培训，从而促进该研究领域的劳动力发展。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。