双月刊

ISSN 1006-9895

CN 11-1768/O4

青藏高原东南局地山谷风环流在一次地形云和降水形成中的作用
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作者单位:

1.中国气象科学研究院;2.中国科学院大气物理研究所

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基金项目:

第二次青藏高原综合科学考察-极端天气气候事件与灾害风险(2019QZKK0104),中国气象科学研究院发展基金(2020KJ016)


Roles of local mountain-valley wind circulation in the formation of an orographic clouds and precipitation event on the southeastern Tibetan Plateau
Author:
Affiliation:

1.Institute of Atmospheric Physics,Chinese Academy of Sciences;2.Key Laboratory for Clouds and Precipitation Physics and Severe Storms,Institute of Atmospheric Physics IAP,Chinese Academy of Sciences CAS;3.State Key Laboratory of Severe Weather LASW,Chinese Academy of Meteorological Sciences,Beijing,and Key Laboratory for Cloud Physics,China Meteorological Administration,Beijing

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    摘要:

    利用第二次青藏高原科学考察及其他数据,结合5层网格嵌套、高分辨率(最高333 m)的WRF可分辨云数值模拟,研究了局地山谷风环流在青藏高原东南林芝地区2019年9月17-18日一次地形云和降水形成过程中的作用。结果表明,此次降水过程由西风槽天气过境造成,林芝位于西风槽底部,具有弱不稳定层结,云和降水过程呈现明显的午后、傍晚和凌晨三个阶段的变化特征,并且发现局地山谷风环流在这三个阶段的变化中具有重要作用。午后阶段,由于山区强烈的太阳辐射加热,首先在山脉阳面产生明显的上坡风,产生了强上谷风环流,在山坡迎风坡受阻挡抬升,并激发出强的地形波,产生了强对流云和降水;傍晚阶段,由于山脉强烈的长波辐射冷却效应,产生的强下坡风在谷底辐合抬升,促进了山谷上空的弱对流、层状云发展;凌晨阶段,下坡风达到最强,产生了强下谷风环流(山风),下坡风在谷底产生强的抬升作用,形成深厚的层状云降水过程。午后阶段的对流云微物理过程主要表现为霰粒子含量高,雨水的来源主要是暖雨过程和霰粒子融化过程,雪粒子很少。傍晚和凌晨的弱对流云和层状云微物理结构相似,主要是雪粒子含量高,雪的融化和暖雨过程是雨水的主要来源。

    Abstract:

    Using the data of the Second Tibetan Plateau Scientific Expedition and numerical simulation results with five-nested domain and high resolution of 333m of WRF model, the role of local mountain-valley wind circulation in an orographic clouds and precipitation event on 17-28, September 2019 in Nyingchi region of southeastern Tibetan Plateau is investigated. The results show that the precipitation event was caused by a passage of westerly trough and Nyingchi station is located at the base of westerly trough with weak unstable stratification. The orographic clouds and precipitation event is found to have obvious three-stage variations in the afternoon, evening and night, and the local mountain-valley wind circulation has an important role in the variation. In the afternoon, the strong solar radiation heating forms obvious upslope winds in the sunny slope firstly, and produces the strong upvalley winds, which are blocked and lifted in the windward slope, and induces strong mountain waves, and strong convective clouds and precipitation. In the evening, the strong longwave radiation cooling forms obvious downslope winds and cause the convergence and lifting process of warmer air in the valley, enhancing the formation and development of weak convection and stratiform clouds on the valley. In the nighttime, the downslope winds reach the strongest, and downvalley winds (mountain winds) are further enhanced, and the strong lifting causes deeper stratiform clouds. The convective clouds in the afternoon have more graupel particles and the main rain sources are from warm rain and graupel melting processes. The snow is very few. However, the similar cloud microphysical properties can be found in the evening and nighttime, the snow become dominant and the main rain sources are from snow melting and warm rain processes.

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历史
  • 收稿日期:2021-12-28
  • 最后修改日期:2022-02-16
  • 录用日期:2022-04-14
  • 在线发布日期: 2022-05-09
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