Baiu Rainband Termination in Atmospheric and Coupled Atmosphere-Ocean Models
Baiu Rainband Termination in Atmospheric and Coupled Atmosphere-Ocean Models
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DOI：
10.1175/jcli-d-13-00231.1
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发表时间：
2013-12-01
影响因子：
4.9
通讯作者：
Xie, Shang-Ping
中科院分区：
文献类型：
--
作者：
Kuwano-Yoshida, Akira;Taguchi, Bunmei;Xie, Shang-Ping
白云雨带是一种夏季雨带，从中国东部穿过日本一直延伸到西北太平洋。利用日本25年再分析(JRA-25)、强迫观测海面温度(SST)的独立大气环流模式(GCM)和大气-海洋GCM(AOGCM)研究了白云雨带的气候学终止。在大气GCM(AGCM)中，北太平洋的白云雨带在7月初突然向北移动并显著减弱，比观测(7月下旬)来得早。对流层中层西风急流及其热力平流解释了白云雨带的这种经向位移，但海面蒸发对降水强度有调制作用。在大气环流模式中，副热带西北太平洋的深对流提前开始，使西风急流在寒冷的洋面上比观测到的更早地向北移动。尽管对流层中层暖平流和垂直积分水汽辐合与西风急流北移之前相似，但冷海上空表面蒸发的抑制抑制了降水。因此，在JRA-25和AGCM北移后，白云雨带突然减弱。在AOGCM中，副热带海温偏冷抑制了深层对流，延缓了西风急流的极地漂移。结果表明，强西风急流和雨带共同引起的西北太平洋上升运动在AOGCM中持续了整个夏季。结果表明，西风急流和下方的海洋蒸发对白云雨带有重要作用，后者表明海洋对这一重要现象有影响。
The baiu rainband is a summer rainband stretching from eastern China through Japan toward the northwestern Pacific. The climatological termination of the baiu rainband is investigated using the Japanese 25-yr Reanalysis (JRA-25), a stand-alone atmospheric general circulation model (GCM) forced with observed sea surface temperature (SST) and an atmosphere-ocean GCM (AOGCM). The baiu rainband over the North Pacific abruptly shifts northward and weakens substantially in early July in the atmospheric GCM (AGCM), too early compared to observations (late July). The midtroposphere westerly jet and its thermal advection explain this meridional shift of the baiu rainband, but the ocean surface evaporation modulates the precipitation intensity. In AGCM, deep convection in the subtropical northwestern Pacific sets in prematurely, displacing the westerly jet northward over the cold ocean surface earlier than in observations. The suppressed surface evaporation over the cold ocean suppresses precipitation even though the midtropospheric warm advection and vertically integrated moisture convergence are similar to those before the westerly jet's northward shift. As a result, the baiu rainband abruptly weakens after the northward shift in JRA-25 and AGCM. In AOGCM, cold SST biases in the subtropics inhibit deep convection, delaying the poleward excursion of the westerly jet. As a result, the upward motion induced by both the strong westerly jet and the rainband persist over the northwestern Pacific through summer in the AOGCM. The results indicate that the westerly jet and the ocean evaporation underneath are important for the baiu rainband, the latter suggesting an oceanic effect on this important phenomenon.