| 项目编号: | 1737813
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| 项目名称: | Collaborative Research: Improving Constraints on Tropical Climate Feedbacks with Inverse Modeling of the Stable Isotopic Composition of Atmospheric Water Vapor |
| 作者: | Robert Field
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| 承担单位: | Columbia University
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| 批准年: | 2017
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| 开始日期: | 2017-08-15
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| 结束日期: | 2020-07-31
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| 资助金额: | 41388
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| 资助来源: | US-NSF
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| 项目类别: | Standard Grant
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| 国家: | US
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| 语种: | 英语
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| 特色学科分类: | Geosciences - Atmospheric and Geospace Sciences
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| 英文关键词: | air
; water vapor
; rh
; climate feedback
; inverse modeling technique
; climate model simulation
; subtropical cloud
; temperature
; research area
; cloud feedback
; warming climate
; climate change
|
| 英文摘要: | The relative humidity (RH) of air in the subtropics, meaning RH in the belts of subsiding air found on either side of the equator, is an important factor in determining the behavior of subtropical clouds and their effects on climate. Air in the subtropics generally enters the region in the upper troposphere after ascending in the deep convective clouds found in the convergence zones near the equator. The RH of the air is largely determined by the coldest temperature it encounters during in-cloud ascent, as condensation dries the air to the saturation moisture value given by its temperature (lower moisture content for colder air). But other factors also influence the RH of the subsiding subtropical air, in particular the air can be moistened by mixing with air from more humid levels closer to the surface. The same RH can be achieved either by a relatively warm last saturation temperature with little mixing or a relatively cold last saturation temperature followed by greater mixing, The two pathways to the same RH can have different implications for cloud feedbacks and RH change in a warming climate.
However, these two pathways can be distinguished by examining the relative concentrations of heavier isotopes of water vapor, water vapor in which one of the hydrogen atoms is replace by deuterium or the oxygen 16 atom is replace by oxygen 18. Roughly speaking, the heavier forms of water vapor evaporate more sluggishly and condense more readily than ordinary H2O, an effect which depends on the temperature at which the evaporation or condensation takes place. Thus, heavy isotopes contain important clues to understanding the processes which set subtropical RH and relate it to subtropical clouds and their climate feedbacks.
With this motivation the PIs examine the isotopic concentration of water vapor in the subtropical mid-troposphere using satellite and ground-based observations as well as climate model simulations. Ground-based observations include measurements taken by the lead PI on the Chajnantor Plateau in Chile (see AGS-1158582). Much of the work is performed using an inverse modeling technique in which an optimal set of parameters (including last saturation temperature and vertical mixing, among others) is determined using a machine learning algorithm that mimics natural selection. The inverse technique is advantageous in that it is computationally inexpensive and can be applied equally well to both observations and model output.
The work has societal relevance as it can lead to a better understanding of the role of subtropical clouds in climate change, a central issue in efforts to anticipate the amount of warming caused by greenhouse gas increases. In addition, the project includes an extensive education and outreach effort through the New Mexico Museum of Natural History and Science in Albuquerque. The museum serves a large Hispanic and Native American population including both inner city and rural communities. The effort engages elementary school students through a summer camp program, middle and high school students through a "junior docent" summer program, and middle and high school teachers through a professional development workshop. In addition, the project provides support and training for a graduate student, thereby providing for the future workforce in this research area. |
| 资源类型: | 项目
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/89290
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| Appears in Collections: | 全球变化的国际研究计划
科学计划与规划
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| Recommended Citation: | |
Robert Field. Collaborative Research: Improving Constraints on Tropical Climate Feedbacks with Inverse Modeling of the Stable Isotopic Composition of Atmospheric Water Vapor. 2017-01-01.
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