摘要: 利用宁夏20个气象站月降水资料、NCEP/NCAR再分析大气资料，以及Hadley中心海表面温度资料，采用经验正交分解、合成分析和典型相关分析等方法，分析了北大西洋海温异常与宁夏春末夏初46月降水异常的关系及其年代际变化。发现北大西洋海温异常与宁夏46月降水之间的相关关系自1961年以来总体呈持续增强趋势，20世纪80年代之前关系不显著，之后相关关系持续显著。20世纪80年代以来，前期冬、春季北大西洋海温异常可引起宁夏46月降水异常，但各月异常存在差异。对应三极子型海温异常正（负）位相，宁夏4月降水偏多（偏少），5月偏少（偏多），6月北少南多（北多南少）。进一步揭示出北大西洋海温异常通过引起北半球欧亚中高纬大范围显著异常波列而影响宁夏降水异常的过程机理，并指出该异常波列从春到夏季节转换中向北推进演变引起了各月降水异常差异的原因。前期持续异常的北大西洋三极子型海温异常正位相，4月在对流层中上层引起的异常波列在乌拉尔山东部和我国东部日本海地区形成显著负、正异常中心，宁夏正好受该西低东高异常环流型影响，低层850 hPa异常偏南风，有利于输送南方暖湿气流，降水偏多。5月、6月随着北半球季节由春到夏季转换，异常波列向北发展推进，5月我国东部日本海地区的高度场正异常中心向北移至贝加尔湖以南地区，宁夏受其控制，低层异常风场辐散，降水偏少。6月贝加尔湖以南地区的高度场正异常中心继续向北移到贝加尔湖以北地区，并与我国东部正异常区分裂，形成两个正异常中心，使得宁夏北部受北高南低高度场异常影响，而南部受西低东高控制，低层宁夏北部异常偏东北风，气流辐散，宁夏南部弱异常偏南风，气流辐合，有利于6月宁夏降水北少南多。对于北大西洋三极子型海温异常负位相则相反。研究结果为深入理解宁夏春末夏初降水异常成因及预测提供了科学参考依据。
Abstract: This study was conducted to reveal the impact and mechanism of the North Atlantic sea surface temperature anomaly (SSTA) associated with Ningxia precipitation and to improve the accuracy of precipitation prediction ability in Ningxia. Based on the monthly precipitation data of 20 meteorological stations in Ningxia, NCEP/NCAR atmospheric data, Hadley center sea surface temperature data, and utilizing empirical orthogonal decomposition, composite, and correlation methods, we studied the relationships and their decadal changes between the North Atlantic SSTA and Ningxia precipitation anomaly from late spring to early summer (April- June). It was found that the relationship had continuously increased since 1961 but nonsignificantly until the 1980s. Since then, the North Atlantic Oceantriple type(NAT) SSTA in early winter and spring has caused precipitation anomalies in Ningxia from April to June but it differs each month. Corresponding to the positive (negative) phase NAT, Ningxia precipitation is more (less) in April, less(more) in May, and less northerly and more southerly (more northerly and less southerly) in June. Furthermore, the mechanism is revealed of NAT affecting Ningxia precipitation anomaly by inducing an atmosphere anomaly wave train in the area from Europe to the Asia-Pacific. The positivephase NAT can induce a wave train with atmosphere circulation anomaly pattern of geopotential heightwest lower and east higherat 500 hPa around Ningxia in April, which is the typical atmosphere anomaly pattern of more precipitation in Ningxia in April. Additionally, at the low layer of 850 hPa, the southerly wind anomalies transform warmer and humid air into Ningxia, contributing to more precipitation. In May and June, with the transition from spring to summer, the abnormal wave train polar shifts. In May, Ningxia is affected by the positive abnormal height field at 500 hPa in Baikal Lake area to East Asia, and the abnormal wind field in the low level of 850 hPa divergence, with less precipitation. In June, the positive height anomaly center at 500 hPa in East Asia continues to develop northward from south to north to Baikal Lake area, and splits from the positive anomaly height in the east of China into two anomaly centers. At 500 hPa, Ningxia north and south areas are affected by the atmospheric circulation pattern of geopotential height anomaly beingnorth higher and south lowerandwest lower and east higher, respectively. Meanwhile, at low level 850 hPa weak northerly and southerly anomaly wind prevails in the north and south area of Ningxia respectively, being with divergence and convergence. All of these atmosphere anomalies are conducive to less precipitation in the north and more in the south of Ningxia. For negative NAT phase, all the atmospheric circulation and precipipation anomalies are vice versa.
| [V1] | 2023-05-30 19:06:05 | ChinaXiv:202305.00255V1 | 下载全文 |
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