Journal of Arid Meteorology ›› 2020, Vol. 38 ›› Issue (5): 755-763.DOI: 10.11755/j.issn.1006-7639(2020)-05-0755

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Numerical Simulation of Influence of Underlying Surface Heterogeneity on a Rainstorm Process in Summer Monsoon Transition Zone of China

REN Yulong1, ZHANG Tiejun1, LIU Yuanpu1, WU Jing2   

  1. 1. Institute of Arid Meteorology, CMA, Key Laboratory of Arid Climatic Change and Reducing Disaster of Gansu Province, Key Laboratory of Arid Climate Change and Disaster Reduction of CMA, Lanzhou 730020, China; 
    2. Lanzhou Central Meteorological Observatory, Lanzhou 730020, China
  • Online:2020-10-30 Published:2020-10-30

夏季风过渡区下垫面非均匀性对一次暴雨影响的数值模拟

任余龙1,张铁军1,柳媛普1,吴晶2   

  1. 1.中国气象局兰州干旱气象研究所,甘肃省干旱气候变化与减灾重点实验室,中国气象局干旱气候变化与减灾重点实验室,甘肃 兰州730020;
    2.兰州中心气象台,甘肃 兰州 730020
  • 作者简介:任余龙( 1976— ) ,男,甘肃秦安人,博士,副研究员,主要从事区域数值模式及模拟研究.
  • 基金资助:
    公益性行业(气象)科研重大专项(GYHY201506001)和甘肃省气象局创新团队(GSQXCXTD-2020-02)共同资助

Abstract: The difference of land-atmosphere energy flux caused by the heterogeneity of underlying surface properties plays an important role in affecting the occurrence of local heavy precipitation. The transition of vegetation is fast in western part of the transition zone of China’s summer monsoon, the nature of vegetation is obviously different, and the surface heterogeneity is strong, so the extreme precipitation is prone to occurrence. In order to explore the influence of underlying surface heterogeneity on strong precipitation in this area, the characteristics of underlying surface were analyzed statistically. And on this basis the sensitivity tests with three or six kinds of landuse type and control test for a typical heavy rainfall process under the influence of the western Pacific subtropical high and cold air from 28 to 29 August 2017 were carried out by using the mesoscale model of WRF3.8 and NCAR-LSM land surface model. The influences of underlying surface change on rainstorm intensity, falling area and flux parameters were studied. The results show that the underlying surface with three to six kinds distributed in transition region of summer monsoon of China. The types of underlying surface were relatively few in eastern part of Qinghai to central Gansu, the heterogeneity was weak, while there were more than six kinds in southeastern part of Northwest China and northern Sichuan, the heterogeneity was strong. The proportion of representative vegetation in a single grid in the model was not high, and the contribution rate to land-atmosphere flux was less than 50%, which indicated that it was not suitable to consider the single underlying surface in calculating land-to-air flux during the heavy rain process. The area of precipitation with different magnitudes was closer to the actual situation with the increase of underlying surface types in the model, and the heterogeneity of land feature physical quantity strengthened in main rain zones. Compared with the control test, the simulated shallow surface temperature, surface heat flux, sensible heat flux and latent heat flux by two sensitivity tests reduced during the daytime, which shrank the bias to some extent, thus decreased convective available potential energy and restrained the occurrence of convective rainfall, further reduced the positive bias of precipitation.

Key words: land surface process, surface heterogeneity, numerical simulation, rainstorm, summer monsoon transition zone

摘要: 下垫面性质非均匀性造成的陆气能量通量差异是影响局地强降水发生的重要原因。中国夏季风过渡区植被过渡快、性质差异大,非均匀性强,是极端降水多发区。为了探究该区域下垫面非均匀性对强降水的影响,在统计分析下垫面特征基础上,对2017年8月28—29日受西太平洋副热带高压西南暖湿气流和中高纬南下冷空气共同影响下的典型暴雨过程,利用中尺度模式WRF3.8及NCAR-LSM陆面模型,设计敏感试验,探讨下垫面种类变化对暴雨强度、落区及通量参数的影响。结果表明:该区域分布着3~6种下垫面,青海东部到甘肃中部下垫面种类相对单一,非均匀性弱,而西北地区东南部、四川北部下垫面种类多在6种以上,非均匀性强。模式单一格点中代表性下垫面类型对陆气通量贡献率不足50%,表明仅用单一下垫面计算陆气通量不适宜。随着模式格点中下垫面种类的增加,不同量级的降水区面积与实况更加接近,且主雨带网格内陆面特征物理量的非均匀性增强。相比于控制试验,两组敏感试验模拟的浅层地表温度、地表热通量、感热通量、潜热通量等在白天均有所减弱,一定程度上消弱了因未考虑下垫面非均匀性而导致的陆面特征物理量误差偏大的现象,从而减小了对流有效位能,抑制对流性降水的产生,一定程度上降低了降水的正偏差。

关键词: 陆面过程, 地表非均匀性, 数值模拟, 暴雨, 夏季风过渡区

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