地形对天山夏季降水影响的模拟

doi:10.7522/j.issn.1000-694X.2015.00116

摘要/Abstract

摘要： 地形对局地云和降水的形成、发展过程起着重要作用。由于天山山脉对偏西、偏北气流的阻挡抬升作用，天山西部（喇叭口地形）和北坡中天山（东西走向）一带成为新疆云和降水最集中的地区。以新疆天山山区2013年8月24-26日一次典型强降水过程为例，利用WRFv3.5.1中尺度模式，通过改变初始场中的天山地形高度进行敏感试验，进而揭示天山地形对夏季山区及邻近区域降水的基本影响机制。控制试验较好地模拟出此次降水的空间分布、中心位置及起止时间、降水极大值高度等特征，与观测结果非常吻合。控制试验与敏感试验对比结果表明，天山地形对降水带分布影响不大，但对强降水中心的范围和量级影响显著。降水量与地形高度和抬升凝结高度的相对大小表现出较好的相关性，地形的阻挡抬升作用导致盛行气流产生较强的垂直上升运动，当达到甚至超过抬升凝结高度时，不稳定能量才得以充分释放，进而引起水凝物含量大大增加。地形对主要冰相水凝物雪晶和冰晶的高度分布影响不大，但对二者的中心值和维持时间影响显著。

关键词: 夏季降水, 天山, 地形动力作用, 抬升凝结高度, 云微物理过程

Abstract: The orographic dynamic effect plays an important role in the generation and development of local cloud and rainfall. Due to the Tianshan Mountain acting on focusing and lifting the westerly or northerly flow, the cloud and rainfall most focus on the west of Tianshan Mountain (trumpet-shaped) and the middle of its north slope (east-west towards) area in Xinjiang. Sensitivity tests of a typical heavy rainfall event occurred along the Tianshan Mountain from 24^th to 26^th August 2013 with different terrain height have been carried out employing the Weather Research and Forecasting (WRF) model to study the influence of the Tianshan Mountain' orographic dynamic effect on summer rainfall. The results show that the simulated spatial distribution, the position and the starting and ending time of the rainfall centers and maximum rainfall height of the control test are relatively consistent with one of observations, which means the model outputs can reflect the characteristics of the orographic precipitation in Tianshan Mountain to some extent. It come a general conclusion that the terrain height play slight roles in the rainfall distribution, whereas significant in the area coverage and grades of the heavy rainfall centers by comparing the control test results and the sensitivity ones. The precipitation is closely related to the relative size between the terrain height and the lift convective level (LCL). Owing to the remarkable blocking and uplifting role of the Tianshan Mountain, the prevailing airflow was lifted upward strongly, the instability release fully and more coagulations generate and maintain when the flow came to even exceeded the LCL, which resulted in the remarkable precipitation enhancement on the windward slope of the Tianshan Mountain. The topography plays little role in the distribution of the main coagulations (namely snow and ice) while remarkable in the center value and maintainance.

Key words: summer rainfall, Tianshan Mountain, orographic dynamic effect, lifting convective level, cloud microphysical process

中图分类号:

P426.6

于晓晶, 赵勇. 地形对天山夏季降水影响的模拟[J]. 中国沙漠, 2016, 36(4): 1133-1143.

Yu Xiaojing, Zhao Yong. Simulation of Orographic Effects on Summer Rain in the the Tianshan Mountains[J]. JOURNAL OF DESERT RESEARCH, 2016, 36(4): 1133-1143.

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