Two regimes of cloud water over the Okhotsk Sea and the adjacent regions around Japan in summer
Two regimes of cloud water over the Okhotsk Sea and the adjacent regions around Japan in summer
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夏季鄂霍次克海及日本周边地区的两种云水状态
DOI：
10.1002/2014jd022536
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
Teruhisa Shimada and Toshiki Iwasaki
中科院分区：
文献类型：
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作者：
河合佑太;高橋芳幸;石渡正樹;西澤誠也;竹広真一;中島健介;富田浩文;林祥介;Teruhisa Shimada and Toshiki Iwasaki
本文利用夏季凉爽的气候指数，推导出鄂霍次克海及其邻近地区夏季具有偶极子结构的两个云水区域。当鄂霍次克高压发展时，由于与鄂霍次克高压相关的下沉运动引起的低层大气稳定性增强，云被限制在一个薄的低层。由此产生的光学薄云允许更多的向下短波辐射到达鄂霍次克海的表面。相比之下，吹向日本群岛和欧亚大陆的低层东风加强了云的形成。这是由于与鄂霍次克高压有关的东风和与白云锋区和太平洋高压有关的南风引起的水汽通量的辐合，以及由于气团的地形抬升。当鄂霍次克海上空发生气旋环流时，靠近海面的一层厚厚的低层云层就会形成。北极海表温度(SST)锋区水汽通量的辐合和较冷的SST促进了雾的形成，与气旋式环流相关的上升运动支持了对流层从低到高的高云水含量。由此产生的光学厚云减少了鄂霍次克海表面向下的短波辐射。在日本周边地区，由于来自陆地的干燥空气和云水的减少，水汽通量出现了差异。
This study derived two regimes of cloud water with a dipole structure between over the Okhotsk Sea and over the adjacent regions around Japan in summer by using a climate index for cool summer. When the Okhotsk high develops, clouds are confined to a thin low‐level layer owing to the enhanced stability in the lower atmosphere induced by the downward motion associated with the Okhotsk high. The resulting optically thin clouds allow more downward shortwave radiation to reach the surface of the Okhotsk Sea. In contrast, the low‐level easterly winds blowing toward the Japanese Islands and the Eurasian continent enhance cloud formation. This is due to the convergence of the water vapor flux induced by the easterly winds associated with the Okhotsk high and the southerly winds associated with the Baiu frontal zone and the Pacific high and due to the orographic uplift of air mass. When a cyclonic circulation occurs over the Okhotsk Sea, a thick layer of low‐level clouds extending close to the sea surface is formed. The convergence of the water vapor flux over the subarctic sea surface temperature (SST) frontal zone and the cool SST promote fog formation, and upward motion associated with the cyclonic circulation supports the high cloud water content from the lower to the upper troposphere. The resulting optically thick clouds reduce the downward shortwave radiation at the surface of the Okhotsk Sea. Over the regions around Japan, water vapor flux diverges owing to dry air originating from land and cloud water decreases.