On the characteristics and climate effects of HV-WCP events over the Kuroshio SST front during wintertime
On the characteristics and climate effects of HV-WCP events over the Kuroshio SST front during wintertime
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DOI：
10.1007/s00382-020-05373-5
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发表时间：
2020-07
期刊：
影响因子：
4.6
通讯作者：
Haokun Bai;Haibo Hu;W. Perrie;Ning Zhang
中科院分区：
文献类型：
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作者：
Haokun Bai;Haibo Hu;W. Perrie;Ning Zhang
冬季东海黑潮海温锋存在被忽略的海表风与降水耦合（HV-WCP）高频变率事件。这种现象的特征是地面风向的调制事件，即从南风异常转变为西北风异常，伴随着风速的增加，并伴随着降水从早晨到晚上的峰值变率。这些事件与中国东南部及其邻近海域降水异常的显著气候效应有关。为了维持这些事件，大尺度环流需要表现出下降的上游季风和削弱垂直混合的行星边界层（PBL）。黑潮对下垫面大气的热力作用减弱，导致黑潮SST锋边界层高度梯度明显。边界层向自由大气输送的大量水汽，产生了降水的初始化和气旋异常。同时，这次降水引起的潜热释放迫使边界层内出现正涡度异常，再次加强了气旋和水汽的向上输送。因此，在黑潮区域，局地环流与降水之间存在着互补关系。由于黑潮SST锋对边界层结构的显著影响，使得高纬西太平洋强度在黑潮区域能够维持其强度。但由于西北季风背景，当耦合系统移出黑潮SST锋区时，高压-西CP事件很快消失。
Neglected High-frequency Variability events of the sea surface Wind Coupled with Precipitation (HV-WCP) events are revealed over the Kuroshio Sea Surface Temperature (SST) front in the East China Sea (ECS) during wintertime. This phenomenon is characterized as modulation events of the surface wind directions, whereby the southerly anomaly changes into a northwest anomaly, accompanied with increasing wind speed, and coupled with decreasing precipitation from morning to night on the day with the peak variability. The events are associated with significant climate effects on the rainfall anomaly over southeastern China and adjacent ocean areas of the ECS. To sustain these events, the large-scale circulation needs to exhibit declines in the upstream monsoon and weakening vertical mixing in the planetary boundary layer (PBL). The Kuroshio thermal effect on the underlying atmosphere becomes prominent due to weakening vertical mixing, which results in pronounced PBL height gradient over the Kuroshio SST front. More plentiful moisture transported from PBL to the free atmosphere, generates the initialization of rainfall and the cyclone anomaly. Meanwhile, the latent heat releasing caused by this precipitation forces positive vorticity anomaly within the PBL, which again strengthens the cyclone and the upward moisture transport. Therefore, a complement between local circulation and rainfall is developed over the Kuroshio region. Due to the significant effect of the Kuroshio SST front on the PBL structure, the HV-WCP intensity is able to maintain its strength over the Kuroshio region. However, because of the northwestern background monsoon, the HV-WCP events vanish quickly when the coupled system moves out of Kuroshio SST frontal region.