Role of the Cold Okhotsk Sea on the Climate of the North Pacific Subtropical High and Baiu Precipitation
Role of the Cold Okhotsk Sea on the Climate of the North Pacific Subtropical High and Baiu Precipitation
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DOI：
10.1175/jcli-d-20-0432.1
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发表时间：
2021-01
影响因子：
4.9
通讯作者：
K. Kawasaki;Y. Tachibana;Tetsu Nakamura;K. Yamazaki
中科院分区：
文献类型：
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作者：
K. Kawasaki;Y. Tachibana;Tetsu Nakamura;K. Yamazaki
一般来说，边缘海的夏季温度比周围大陆的温度低，因为陆地和海洋之间的热容量存在巨大差异。鄂霍次克海直到初夏都被海冰覆盖，夏天比周围的大陆冷得多。因此，鄂霍次克海位于夏季中纬度所有边缘海中温度差异最大的地区之一。鄂霍次克海上空的冷空气可能会对遥远的夏季气候产生影响，例如作为冷空气平流的来源，导致日本农作物收成不佳。在这里，我们研究的作用鄂霍次克海的初夏气候的北太平洋西部通过一个理想的数值实验，人工改变模型的默认海洋条件在鄂霍次克海的土地覆盖的条件。模拟结果表明，鄂霍次克海的存在通过加强北太平洋副热带高压西缘的北向水汽通量，增加了梅雨锋的降水。鄂霍次克的影响进一步延伸到北美西部，加强的急流与风暴路径延伸到那里。这种远程的影响是可以实现的，通过反馈从一个短暂的涡流异常，激活的表面温度梯度之间的寒冷的鄂霍次克海和温暖的太平洋。研究结果表明，鄂霍次克海的存在加强了东亚夏季风。
Summertime temperatures in marginal seas are, in general, colder than on the surrounding continent because of the large contrast in heat capacity between the land and the ocean. The Okhotsk Sea, which is covered by sea ice until early summer, is much colder than the surrounding continent in summer. The Okhotsk Sea is thus located in an area with one of the largest temperature contrasts of all the marginal seas in summertime midlatitudes. Cooled air over the Okhotsk Sea may have an impact on remote summer climates, such as by serving as the source of cold-air advection that results in a poor crop harvest in Japan. Here, we examine the role of the Okhotsk Sea on the early summer climate of the western part of the North Pacific through an ideal numerical experiment by artificially changing the model’s default oceanic condition in the Okhotsk Sea to a condition of land cover. Simulation results reveal that the presence of the Okhotsk Sea increases precipitation of the baiu/mei-yu front through strengthening of the northward moisture flux at the western edge of an intensified North Pacific subtropical high. The Okhotsk influence farther extends toward western North America to which the strengthened jet stream with a storm track extends. This remote influence is achievable through feedback from a transient eddy anomaly that is activated by the surface temperature gradient between the cold Okhotsk Sea and the warm Pacific Ocean. The findings imply that the existence of the Okhotsk Sea strengthens the East Asian summer monsoons.