Fram Strait Marine Cold Air Outbreaks in CARRA and ERA5: Effects on Surface Turbulent Heat Fluxes and the Vertical Structure of the Troposphere

IF 3.8 2区 地球科学 Q2 METEOROLOGY & ATMOSPHERIC SCIENCES
Nils Slättberg, Sandro Dahlke, Marion Maturilli
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Abstract

Marine Cold Air Outbreaks (MCAOs) have a profound influence on atmospheric conditions and the surface-atmosphere heat exchange in Fram Strait and Svalbard. Comparing the global reanalysis ERA5 to its novel Arctic counterpart CARRA for November–March 1991–2020, we investigate the surface turbulent heat fluxes and the spatial characteristics associated with MCAO conditions. We find that the sensible heat flux from the surface to the atmosphere is substantially higher in CARRA while the latent heat flux is higher in ERA5. For sensible heat flux, the differences scale with the magnitude, leading to maximum disagreement over the ice-free ocean where the heat flux is high. Accounting for the varying heat flux magnitude over different surface types, we find the largest relative disagreement over sea ice. During MCAOs, negative anomalies in temperature and specific humidity are present throughout most of the troposphere in both reanalyses. Over the studied period, sea ice decline has caused positive trends in the surface-atmosphere potential temperature difference forming the basis of the MCAO index, leading to higher heat fluxes around much of Svalbard. In ice-free Fram Strait however, both reanalyses show negative trends in the MCAO index and the heat fluxes in January, when the increase in potential temperature is larger at 850 hPa than at the surface. Finally, large differences between two individual MCAO cases are found in reanalysis heat flux variability and radiosonde-derived atmospheric conditions over Svalbard.

Abstract Image

在CARRA和ERA5的Fram海峡海洋冷空气爆发:对地面湍流热通量和对流层垂直结构的影响
海洋冷空气爆发(MCAOs)对弗拉姆海峡和斯瓦尔巴群岛的大气条件和地表-大气热交换有着深远的影响。对比1991-2020年11月- 3月的全球再分析ERA5和北极地区的CARRA,我们研究了与MCAO条件相关的地表湍流热通量和空间特征。我们发现,CARRA地区地表到大气的感热通量明显较高,而ERA5地区的潜热通量较高。对于感热通量,差异与量级成正比,在热通量高的无冰海洋上差异最大。考虑到不同地表类型的不同热通量大小,我们发现海冰的相对差异最大。在MCAOs期间,在两次再分析中,对流层大部分地区都存在温度和比湿度的负异常。在研究期间,海冰减少导致形成MCAO指数基础的地表-大气位温差呈正趋势,导致斯瓦尔巴群岛大部分地区的热通量增加。在无冰的海峡,MCAO指数和热通量在1月份呈负趋势,850 hPa的势温增幅大于地面。最后,在再分析热通量变率和无线电探空衍生的斯瓦尔巴群岛大气条件方面,两个MCAO个案之间存在很大差异。
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来源期刊
Journal of Geophysical Research: Atmospheres
Journal of Geophysical Research: Atmospheres Earth and Planetary Sciences-Geophysics
CiteScore
7.30
自引率
11.40%
发文量
684
期刊介绍: JGR: Atmospheres publishes articles that advance and improve understanding of atmospheric properties and processes, including the interaction of the atmosphere with other components of the Earth system.
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