Summertime midlatitude weather and climate extremes induced by moisture intrusions to the west of Greenland
Summertime midlatitude weather and climate extremes induced by moisture intrusions to the west of Greenland
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DOI：
10.1002/qj.3610
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发表时间：
2019-07
影响因子：
8.9
通讯作者：
Cory F. Baggett;Sukyoung Lee
中科院分区：
文献类型：
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作者：
Cory F. Baggett;Sukyoung Lee
2010年夏季的特点是极端天气和气候，如俄罗斯西部的热浪和巴基斯坦的洪水。最近的一项研究发现，夏季被一个特殊的200 hPa位势高度模式所主导，其特征是一个异常的罗斯比波列，其脊以格陵兰岛、欧洲和俄罗斯为中心。这种模式的日频率最近急剧增加，与1998-2014年（P2）和1979-1997年（P1）之间200 hPa位势高度场的平均状态差非常相似。由于异常波列通常是由局部非绝热加热驱动的，因此本研究验证了P2 - P1型是否是由格陵兰附近的非绝热加热异常引起的。研究发现，在P2期间，格陵兰岛以西巴芬湾的海冰浓度下降，海面温度上升，但表面潜热通量实际上是向下增加的，这表明表面过程可能不是非绝热加热的来源。相反，P2观测到巴芬湾上空垂直整合的水平潜热通量辐合增加，导致水汽凝结和潜热。因此，对流层中环流建立了非绝热加热。在巴芬湾理想化的加热条件下，一组初始值计算结果显示，解与P2 - P1模式非常相似，并提供了一个合理的解释，说明为什么这种模式发生得更频繁。这项研究表明，北极的变化可能是由中纬度地区的水汽输送引起的，而这些变化反过来又会在遥远的中纬度地区诱发极端天气和气候。
The summer of 2010 was characterized by weather and climate extremes such as the western Russia heatwave and the Pakistan floods. A recent study found that summer was dominated by a particular 200 hPa geopotential height pattern featuring an anomalous Rossby wave train with ridges centred over Greenland, Europe and Russia. The daily frequency of this pattern has dramatically increased recently and closely resembles the mean‐state difference in 200 hPa geopotential height fields between 1998–2014 (P2) and 1979–1997 (P1). Because anomalous wave trains are often driven by localized diabatic heating, it is tested in this study whether the P2 minus P1 pattern is caused by diabatic heating anomalies near Greenland. While it is found that sea ice concentrations declined and sea‐surface temperatures rose over Baffin Bay to the west of Greenland during P2, surface latent heat fluxes actually increased downward, indicating that surface processes were likely not the source of diabatic heating. Rather, an increase in vertically integrated horizontal latent‐heat flux convergence over Baffin Bay was observed in P2, which led to the condensation of water vapour and latent heating. Thus, the mid‐tropospheric circulation established the diabatic heating. A set of initial‐value calculations with idealized heating over Baffin Bay show solutions that remarkably resemble the P2 minus P1 pattern and provide a plausible explanation as to why the pattern has been occurring more frequently. This study demonstrates that changes in the Arctic can arise from moisture transport from the midlatitudes, and, in turn, these changes can induce weather and climate extremes in distant midlatitude regions.