The 3D Structure of Northern Hemisphere Blocking Events: Climatology, Role of Moisture, and Response to Climate Change
The 3D Structure of Northern Hemisphere Blocking Events: Climatology, Role of Moisture, and Response to Climate Change
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北半球阻塞事件的 3D 结构：气候学、水分的作用以及对气候变化的响应
DOI：
10.1175/jcli-d-21-0141.1
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发表时间：
2021
影响因子：
4.9
通讯作者：
Hassanzadeh, Pedram
中科院分区：
文献类型：
--
作者：
Nabizadeh, Ebrahim;Lubis, Sandro W.;Hassanzadeh, Pedram
为了更好地了解阻塞事件的动态和影响，需要进一步研究其三维结构。我们提出了一个全面的复合分析块的三维结构及其对未来气候变化的响应在北太平洋，北大西洋和俄罗斯在夏季和冬季使用再分析和两个大型集合数据集CESM 1和GFDL-CM 3。在再分析中，海洋和陆地上的异常风在对流层和平流层是等效正压的，温度异常在整个对流层是正的，在平流层下部是负的。主要的季节性和区域性差异是，块在冬季更大和/或更强;在海洋，温度异常向西移动，由于潜热加热。分析温度趋势方程表明，在所有三个部门，绝热变暖，由于沉降是正温度异常的主要驱动力;然而，根据季节和地区，纬向热平流和潜热加热可能也有领先的顺序的贡献。这两个GCM被发现非常好地再现了气候的三维结构，但有时不同意未来的变化。总体而言，未来夏季所有领域的响应都在减弱（特定湿度除外），尽管对近地面温度的影响不一定减弱;例如，俄罗斯上空阻塞驱动的近地面变暖加剧。冬季的反应是加强所有领域，在某些情况下，除了温度。在冬季，位势高度和温度的响应向西移动，很可能是由于潜热加热。结果突出了块的三维结构的过程级分析的重要性，以更好地理解所产生的极端温度及其未来的变化。
To better understand the dynamics and impacts of blocking events, their 3D structure needs to be further investigated. We present a comprehensive composite analysis of the 3D structure of blocks and its response to future climate change over the North Pacific, the North Atlantic, and Russia in summers and winters using reanalysis and two large-ensemble datasets from CESM1 and GFDL-CM3. In reanalysis, over both ocean and land, the anomalous winds are equivalent-barotropic in the troposphere and stratosphere, and temperature anomalies are positive throughout the troposphere and negative in the lower stratosphere. The main seasonal and regional differences are that blocks are larger and/or stronger in winters; over oceans, the temperature anomaly is shifted westward due to latent heating. Analyzing the temperature tendency equation shows that in all three sectors, adiabatic warming due to subsidence is the main driver of the positive temperature anomaly; however, depending on season and region, meridional thermal advection and latent heating might have leading-order contributions too. Both GCMs are found to reproduce the climatological 3D structure remarkably well, but sometimes disagree on future changes. Overall, the future summertime response is weakening of all fields (except for specific humidity), although the impact on near-surface temperature is not necessarily weakened; for example, the blocking-driven near-surface warming over Russia intensifies. The wintertime response is strengthening of all fields, except for temperature in some cases. Responses of geopotential height and temperature are shifted westward in winters, most likely due to latent heating. Results highlight the importance of process-level analyses of blocks’ 3D structure for improved understanding of the resulting temperature extremes and their future changes.
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