摘要
2003年淮河流域梅雨期(6月29日～7月11日)的强降水过程有三次:6月29日～7月1日、7月3～5日及7月8～11日。本文对7月8日12时～9日12时期间湖南、安徽和江苏发生的强降水过程的中尺度数值模式MM5的输出资料进行了诊断分析。分析结果表明:除大尺度系统的配置有利于此次降水的发生以外,此次降水主要发生在由西南及偏南暖湿气流与偏北气流辐合形成的梅雨锋切变线上,切变线上辐合中心处生成并发展的两个中尺度低涡是造成降水的直接系统。低空西南风急流形成了从孟加拉湾、南海至华东地区的强水汽输送带以及湖南、安徽和江苏的水汽辐合中心,为暴雨创造了十分有利的水汽条件。在低层切变线的辐合中心处有两个低涡分别生成或发展,并沿切变线向东北方向移动,这两个低涡生成的位置是低空急流左前侧急流达到极值的区域(也是正涡度中心区),其生成可能与低空急流的加强有关。在低涡附近,低层水汽辐合较强,且对流层中低层形成了强正涡度中心和强散度中心相耦合的动力结构,并有强上升运动维持,使得低层辐合的水汽被抬升到对流层高层,有利于暴雨的发生。
Based on the data collected from the 325-m meteorological tower operated by the Institute of Atmospheric Physics of Chinese Academy of Sciences in the northern suburbs of Beijing during the period from December 1993 through January 1994,the characteristics of the turbulent fluxes measured at the heights of 47 m and 120 m,and their variations with respect to the wind speed and stability parameters during the passage of strong wind are analyzed.The results indicated that the strong wind has great influence on the turbulent transfer in the near surface layer.There is a short period before the strong wind when the momentum flux is upward,and the heat flux is downward.The turbulent fluxes during the strong wind episode are obviously larger than those after the passage of strong wind.The horizontal turbulent fluxes and the energy increment are larger than the vertical values.The correlations between the turbulent fluxes and the wind speed,and turbulent kinetic energy increase rapidly when the wind speed exceeds the threshold value.The low-frequency component in the spectrum of turbulence rises,and the turbulent spectral curve widens.The energy budget in the surface layer can be strongly influenced by the strong wind.
出处
《大气科学》
CSCD
北大核心
2010年第3期629-639,共11页
Chinese Journal of Atmospheric Sciences
基金
国家重点基础研究发展规划项目2009CB421505
科技部公益性行业(气象)科研专项项目GYHY200906004
国家自然科学基金资助项目40975034
国家科技支撑计划项目2008BAC37B01
关键词
切变线
低涡
结构分析
strong wind
turbulent structure
sensible heat flux
momentum flux
