摘要
利用地面加密自动站逐小时观测资料和ERA-Interim再分析资料,分析了2011年6月江淮流域的5次强降水过程和西南低空急流的日变化特征。发现强降水的日变化与西南低空急流的日变化一致:02—08时增强,14时减弱。这主要是由于夜间边界层内的惯性振荡,导致西南低空急流增强从而使得梅雨锋水汽通量辐合增强,降水增强;而白天由于边界层混合摩擦力增大,致使西南低空急流减弱或消失,降水减弱。WRF数值模拟试验不仅重现了观测的日变化特征,而且证实了江淮暴雨和西南低空急流的日变化主要是由非地转风的日变化造成:白天边界层混合强,风为次地转;而夜间边界层混合消失,气压梯度力和科氏力平衡的惯性振荡使得风为超地转。
This study investigates the characteristics of diurnal variations of southwesterly low-level jet （LLJ） and five heavy rainfall events over Yangtze-Huaihe River basin during June 2011 by analyzing the ERA-interim reanalysis data and surface automatic weather stations data. It is found that the southwesterly LLJ and the precipitation have the same evident diurnal variations in the five processes, which is strong in nocturnal-to-early morning hours （0200---0800 BST） and weak in the afternoon （1400 BST） hours. It is mainly attributed to inertial oscillation at nighttime and vertical mixing in the boundary layer during daytime. The enhancement of the southwesterly LLJ leads to the enhancement of the Meiyu front water vapor convergence, which contributes to the enhancement of rainfall at nighttime. Then with the reduction or disappearance of the southwesterly LLJ, the rainfall also weakens. The WRF numerical simulation successfully reproduces the observed evolution of precipitation and the southwesterly LLJ, and it is proved that the diurnal variations of the LLJ and rainfall are mainly attributed to the diurnal variations of ageostrophic winds. With the enhancement of the vertical mixing in the boundary layer during daytime, the winds become subgeostrophic. With the disappearance of the vertical mixing at nighttime, inertial oscillation under the balance of the pressure gradient force and Carioles force turn the winds into supergeotrophic winds.
出处
《热带气象学报》
CSCD
北大核心
2017年第5期750-761,共12页
Journal of Tropical Meteorology
基金
国家自然科学基金项目(91437104)
国家973项目(2012CB417202)
公益性行业(气象)科研专项(GYHY201406008)
留学人员科技活动项目(1540409921)共同资助
关键词
梅雨锋暴雨
西南低空急流
日变化特征
非地转风
太阳加热
Meiyu front heavy rainfall
southwesterly LLJ
characteristics of diurnal Variations
ageostrophic winds
solar heating
