气候变化领域集成服务门户(CCPortal): Reduction in the Tropical High Cloud Fraction in Response to an Indirect Weakening of the Hadley Cell

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DOI	10.1029/2023MS003985
	Reduction in the Tropical High Cloud Fraction in Response to an Indirect Weakening of the Hadley Cell
	Natchiar, S. R. Monisha; Webb, Mark J.; Lambert, F. Hugo; Vallis, Geoffrey K.; Morcrette, Cyril J.; Holloway, Christopher E.; Sergeev, Denis E.; Boutle, Ian
发表日期	2024
EISSN	1942-2466
起始页码	16
结束页码	5
卷号	16 期号:5
英文摘要	Tropical high cloud cover decreases with surface warming in most general circulation models. This reduction, according to the stability-iris hypothesis, is thermodynamically controlled and linked to a decrease in the radiatively-driven clear-sky convergence, when the peak anvil clouds rise because of the rising isotherms. The influence of the large-scale dynamical changes on the tropical high cloud fraction remains difficult to disentangle from the local thermodynamic influence, given that the mean meridional circulation remains inextricably tied to the local thermodynamic structure of the atmosphere. However, using idealized general circulation model simulations, we propose a novel method to segregate the dynamical impact from the thermodynamic impact on the tropical high cloud fraction. To this end, our investigation primarily focuses on the mechanisms underpinning changes in the high cloud cover in the deep tropics in response to extratropical surface warming, when the tropical sea surface temperatures remain invariant. Net convective detrainment of ice cloud condensates decreases at the peak detrainment region, without a rise in its altitude. We also find that the importance of depositional growth of ice cloud condensates in controlling the high cloud fraction response in the deep tropics varies with altitude. The cloud feedback associated with changes in the tropical high cloud cover is one of the major uncertainties in calculating the current estimates of climate sensitivity, which is a measure of how much the Earth's average surface temperature would increase if we double the amount of atmospheric carbon dioxide. When the surface becomes warmer in the tropics, the tropical high cloud cover decreases. However, this raises an important question: how do circulation changes independent of the temperature changes within the tropics impact the tropical high cloud cover? Using idealized general circulation model simulations, we found that the tropical high cloud fraction decreases as a result of circulation changes induced by extratropical warming, even when the tropical sea surface temperatures are held constant. Both convective and cloud microphysical processes play significant roles in controlling the changes in tropical high cloud fraction, and their relative importance varies with altitude. Understanding the different factors responsible for the changes in high cloud cover is important, as the area covered by these tropical high clouds can affect how much the Earth warms under climate change. An indirect weakening of the Hadley circulation decreases the convectively-detrained ice cloud condensates in the deep tropics A concurrent reduction in the net vertical transport of water vapor limits the depositional growth of ice cloud condensates The relative influence of depositional growth to net convective detrainment on the tropical high cloud response is altitude-dependent
英文关键词	tropical; anvil cloud fraction; warming; extratropical; Hadley circulation; tropical ascent
语种	英语
WOS研究方向	Meteorology & Atmospheric Sciences
WOS类目	Meteorology & Atmospheric Sciences
WOS记录号	WOS:001232563000001
来源期刊	JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/306277
作者单位	University of Exeter; Met Office - UK; University of Reading; University of Exeter
推荐引用方式 GB/T 7714	Natchiar, S. R. Monisha,Webb, Mark J.,Lambert, F. Hugo,et al. Reduction in the Tropical High Cloud Fraction in Response to an Indirect Weakening of the Hadley Cell[J],2024,16(5).
APA	Natchiar, S. R. Monisha.,Webb, Mark J..,Lambert, F. Hugo.,Vallis, Geoffrey K..,Morcrette, Cyril J..,...&Boutle, Ian.(2024).Reduction in the Tropical High Cloud Fraction in Response to an Indirect Weakening of the Hadley Cell.JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS,16(5).
MLA	Natchiar, S. R. Monisha,et al."Reduction in the Tropical High Cloud Fraction in Response to an Indirect Weakening of the Hadley Cell".JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS 16.5(2024).