摘要
地形降水是我国西北地区最主要的降水类型之一,加深其形成机理的认识对提高预报能力有重要意义。本文以贺兰山东麓地区20次暴雨过程中的高空环境参数为基础构建不同类型风场垂直分布结构,利用WRF模式中的em_hill2d_x模块开展不同类型风场对降水模态影响的理想数值试验。结果表明:(1)有/无风垂直切变的两种不同类型干气流过山后其迎风坡均表现为地形对迎风坡气流的抬升作用,而背风坡波动表现出明显不同的变化特征,单层均一气流条件下背风坡主要表现为沿垂直方向传播的过山波,低空存在风切变的风场条件下背风侧主要体现背风波的特征,重力波呈水平与垂直传播共存的特征,且随着低空风切变增强水平传播的背风波特征越来越明显。(2)单层均一湿气流条件下模拟的降水主要位于迎风侧,背风侧在较强的下坡风影响下,降水强度相对较弱。当风速增大至10m·s^(-1)以上时,迎风侧云水含量大值区向山顶汇集,降水强度显著增强。低空存在风切变湿气流过山试验结果显示在迎风侧与背风侧均存在较强的降水中心,背风坡存在一深对流系统,随着风速增大,两侧降水均增强。(3)在低空东风高空西风的条件下,背风侧降水显著减弱,降水更加集中于上游山顶附近,强度也有一定的增强,这与高空西风的出现使迎风坡上升气流加强,且不利于水汽向下游的输送有关,这是贺兰山脉两侧降水特征存在显著差异的主要原因之一。
Topographic precipitation is one of the main types of precipitation in northwest China.It is therefore of great significance to achieve a deeper understanding of the mechanism of topographic precipitation formation to improve forecasting ability.In this study,the vertical distribution structure of different types of wind fields was constructed based on the high-altitude environmental parameters during 20 heavy rains around the eastern foot-hills of Helan Mountain,and the em_hill2d_x module of WRF model was used to conduct ideal numerical experi-ments on the influence of different types of wind field on precipitation distribution.The results show that:(1)The dry air flow of two different types of wind fields(with/without wind shear)on the windward slope of the moun-tain range has an uplift effect of terrain on the windward slope air flow.The leeward slope fluctuation showed dif-ferent characteristics;under the condition of single layer uniform flow,the leeward slope is mainly represented by a mountain wave propagating in the vertical direction.Under the wind field with low-level wind shear,the lee-ward side mainly reflects the characteristics of the dorsal wave,and the gravity wave has the characteristics of co-existing horizontal and vertical propagation.With the increase in low-level wind shear,the characteristics of the horizontal propagation of the dorsal wave become increasingly obvious.(2)The simulated precipitation under the condition of a single layer of uniform wet airflow is mainly located on the windward side,and the precipitation in-tensity is relatively weak on the leeward side under the influence of strong downhill wind.When the wind speed increases to more than 10 m·s^(-1),the large cloud water content area on the windward side converges to the top of the mountain,and the precipitation intensity increases significantly.In the presence of low-level wind shear flow moving over the mountains,the test result shows that both the windward and leeward side there is a strong rain-fall center,with a deep co
作者
李超
隆霄
曹怡清
韩子霏
王号
郑景元
LI Chao;LONG Xiao;CAO Yiqing;HAN Zifei;WANG Hao;ZHENG Jingyuan(College of Atmospheric Sciences,Lanzhou University,Lanzhou 730000,Gansu,China;Hebei Meteorological Disaster Prevention Center,Shijiazhuang 050021,Hebei,China;Hebei Climate Center,Shijiazhuang 050021,Hebei,China)
出处
《干旱区研究》
CSCD
北大核心
2024年第8期1272-1287,共16页
Arid Zone Research
基金
国家自然科学基金(42175088,41965001)
宁夏回族自治区科技创新领军人才培养工程(2021GKLRLX05)。
关键词
地形降水
理想试验
重力波
对流系统
贺兰山
topographic precipitation
ideal test
gravity wave
convection system
Helan Mountain
