Potential Changes of Surface Latent Heat Flux over Oceans under Global Warming

NCUIR > College of Earth Sciences > Department of Atmospheric Sciences and Graduate Institute of Atmospheric Physics > Department of Earth Sciences > Item 987654321/85594

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/85594

Title:	Potential Changes of Surface Latent Heat Flux over Oceans under Global Warming
Authors:	李亭萱;Lee, Ting-Hsuan
Contributors:	大氣科學學系
Keywords:	蒸發;潛熱;SLHF;Evaporation
Date:	2021-07-15
Issue Date:	2021-12-07 11:06:48 (UTC+8)
Publisher:	國立中央大學
Abstract:	潛熱通量(蒸發)為海表面與大氣邊界層能量交換過程，在氣候系統能量平衡中扮演重要角色，本篇研究旨在探討海表面潛熱通量在全球暖化下之可能變化。本篇研究中我們使用CMIP5 RCP8.5情境下選取適合模式，透過前後二十年氣候平均的差異來做結果探討。以往研究蒸發的變化有兩主要理論，一為主張全球暖化下蒸發的變化主要是透過增溫的貢獻，即熱力效應；另一理論則認為，主要貢獻項應為風速的加強，即為動力效應。基於上述兩種理論，本篇文章探討全球暖化下，表面潛熱通量的改變以及上述兩貢獻項在全球尺度上的影響，其中以東太平洋尤為顯著。透過將蒸發表示式分解，使用於全球以及熱帶海洋上做分析，我們發現熱力效應主導了潛熱通量的變化，在全球海洋上此項有著普遍為正的貢獻項。相比於熱力貢獻，動力項卻有著正負貢獻分布較不統一的結果，尤其在東南太平洋海域，此項有著顯著的正貢獻。由緯向平均之海溫和近海面空氣溫度差異，發現南北半球有著不對稱的暖化趨勢；而這主要來自冰的分布和特徵所造成。北半球高緯度海面浮冰，相較於南半球高緯度分布的冰層而言，在暖化情境下較容易被融化；因此，北半球的海溫和近海面空氣溫度的增加會比南半球來的顯著，這樣不對稱的溫度分布會產生梯度差異，而影響了壓力梯度場，導致南半球副熱帶高壓增強，造成了潛熱通量變化中動力項在局部地區主導的結果。 ;The purpose of this study is to investigate changes of the surface latent heat flux (SLHF) (or namely the evaporation), representing the latent heat exchanges between the atmosphere and the underlying ocean, under the influence of anthropogenic global warming. Here, we focus on the changes between the first and last twenty-year period of the 21th in CMIP5 multi-model ensemble mean with the RCP8.5 warming scenario. As the two main theories of the evaporation change suggested that one of the vital factor is contributed to the warming temperature, referring to as the thermal effect; while the other is due to the wind speed change, also referring to as the dynamic effect. The present study examines how SLHF might change over oceans under global warming and the roles played respectively by the above two factors. After conducting the decomposition of the original SLHF bulk formula on global and tropical oceans, we find that the thermal effect dominates the SLHF change with a generally positive contribution over global oceans. Comparing to the thermal effect, the dynamic effect nonetheless exhibits a mix of positive and negative contribution depending on regions, with a significantly positive contribution to the SLHF change over the Southeast Pacific. From the zonal mean differences between sea surface temperature (SST) and air temperature (Ta), we note that the asymmetric warming between the two hemispheres was primarily due to the differences in ice thickness. It would be easier to melt the floating sea ice over the Arctic relative to the Antarctic which is permanently covered by thick land ice. Therefore, there is a great potential of warming in SST and Ta over the northern hemisphere compared to the southern hemisphere. The asymmetric SST warming tendency would induce various meridional SST gradients, leading to a stronger southern hemispheric Subtropical High and the different dynamic response in SLHF.
Appears in Collections:	[Department of Atmospheric Sciences and Graduate Institute of Atmospheric Physics ] Department of Earth Sciences

Files in This Item:

File	Description	Size	Format
index.html		0Kb	HTML	109	View/Open

社群 sharing

Loading...