Moisture transport to a typical transitional climate zone in North China forced by atmospheric and oceanic internal variability under the background of global warming
Moisture transport to a typical transitional climate zone in North China forced by atmospheric and oceanic internal variability under the background of global warming
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DOI：
10.1002/joc.6999
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发表时间：
2021-02
期刊：
影响因子：
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通讯作者：
Linhao Zhong;L. Hua;Yao Yao-Yao;Jinming Feng;Tianbao Zhao
中科院分区：
文献类型：
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作者：
Linhao Zhong;L. Hua;Yao Yao-Yao;Jinming Feng;Tianbao Zhao
中国中北部（34° ~ 42 ° N，95° ~ 107 ° E）是典型的西风带和季风带的过渡带，在全球变暖的背景下，降水呈现多时间尺度变化。因此，根据1979-2015年的再分析数据分析了NCC水分输送（NMT）。利用空间无界动力循环模式，识别了华北夏季降水的主要NMT路径和水汽来源。NMT的趋势模式表现为西北输送减弱但西南输送增强的跷跷板模式，表明中纬度西风带和印度季风之间的相互作用。NMT趋势型的时间演变表现出叠加在长期趋势上的年际和年代际变率，分别对应于大气和海洋物理过程。偏最小二乘回归分析表明，大气和海洋内部气候变率（ICV）可以很好地解释NMT趋势型的时间演变。在年际尺度上，由环全球遥相关（CGT）、东大西洋遥相关（EA）和东大西洋/俄罗斯西部遥相关（EAWR）组成的大气ICV形成欧亚波列，通过欧洲阻塞流减弱西风输送，通过具有纬向偶极子结构的局地环流异常增强西南风输送。然而，由大西洋年代际振荡（AMO）和太平洋年代际振荡（PDO）组成的海洋ICV在几十年的时间尺度上产生影响，使北大西洋中纬度西风急流减速，为欧洲阻塞的形成提供了有利的上游背景条件，并进一步维持了大气ICV引起的欧亚波列。因此，在全球变暖的背景下，不同时间尺度的海洋和大气内部过程耦合有助于NCC降水的长期变化。
North Central China (NCC) (34°–42°N, 95°–107°E), a typical transitional climate zone between westerlies and monsoon, shows multiple time‐scale variations in precipitation under the background of global warming. Thus, NCC moisture transport (NMT) was analysed based on reanalysis data from 1979–2015. By using the spatially unbounded dynamic recycling model, main NMT pathways and moisture sources were identified for the summer rainfall of NCC. The trend pattern of NMT manifests as a seesaw pattern with a weakening northwesterly transport but an enhancing southwesterly transport, suggesting an interaction between the mid‐latitude westerlies and the Indian monsoon. The temporal evolution of the NMT trend pattern exhibits interannual and multidecadal variability superimposed on long‐term trends, which correspond to the atmospheric and oceanic physical processes, respectively. The partial least squares regression analysis demonstrated that the temporal evolution of NMT trend patterns can be well explained by atmospheric and oceanic internal climate variability (ICV). At interannual time scales, the atmospheric ICV, composed of the circumglobal teleconnection (CGT) and East Atlantic (EA) and East Atlantic/Western Russia (EAWR) teleconnections, forms a Eurasian wave train that weakens westerly transport via the Europe blocking flow and enhances southwesterly transport via local circulation anomalies with a zonal dipole structure. However, oceanic ICV, composed of the Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO), exerts influence on a multidecadal time scale to decelerate the mid‐latitude westerly jet over the North Atlantic, providing favourable upstream background conditions for the formation of the Europe blocking and further maintaining the atmospheric ICV‐induced Eurasian wave train. Thus, the internal oceanic and atmospheric processes at different time scales couple to contribute to long‐term changes in precipitation over NCC under the background of global warming.