摘要
在以往研究的基础上,本文把对流涡度矢量的垂直分量、水平散度和广义位温的垂直梯度有机地结合起来,引入热力切变平流参数的概念。本文针对两次强降水过程,利用NCEP/NCAR全球最终分析资料对热力切变平流参数进行诊断分析,结果表明,热力切变平流参数能够比较准确地综合表征雨区上空水平风场切变和湿等熵面漏斗状向下伸展等动力学和热力学典型的垂直结构特征,因而该参数与降水系统的发展演变密切相关,与观测的6小时累积地面降水区存在一定的对应关系;在空间水平分布和时间演变趋势上,热力切变平流参数的异常值区覆盖着观测的6小时累积地面降水区;该参数在降水区内表现为强信号,而在非降水区表现为弱信号。影响热力切变平流参数发展演变的因素分析表明,该参数倾向方程中通量散度项的异常值区覆盖着观测的6小时累积地面降水区,表明雨区内通量散度项导致的热力切变平流参数变化比较明显,其中纬向风速与经向风速相互作用的贡献是不容忽略的。
On the basis of previous studies,a thermodynamic shear advection parameter is defined by involving vertical component and horizontal divergence of convective vorticity vector,and vertical gradient of generalized potential temperature.The parameter is characterized by describing dynamical characteristics of horizontal wind shear and thermodynamic characteristics of downward funnel-shaped moist isentropic surface over extreme weather regions.The parameter is calculated with NCEP/NCAR global final analysis data in two heavy-rainfall events in China.The result shows that the positive high-value area of the parameter vertically integrated always covered the observed 6-h accumulated surface rainfall.Both of them shared a similar horizontal distribution pattern and an analogous temporal evolution trend.The parameter in the precipitation zone showed a strong signal,while it presented a weak signal in the non-rainfall areas.Since the parameter is capable of presenting typical vertical structure of dynamical and thermodynamic fields over extreme weather area,it is closely related to the precipitation weather system leading to heavyrainfall.This is the reason that there is a corresponding relationship between the parameter and the observed 6-hour accumulative rainfall areas.It was also shown that the precipitation area was covered by the abnormal-value region of flux divergence term in the parameter equation.This indicated that the flux divergence prompted the parameter to revolve over the precipitation area.The contribution to the local change of the parameter from the interaction between zonal and meridional winds in the flux divergence term is chief.
出处
《大气科学》
CSCD
北大核心
2010年第6期1201-1213,共13页
Chinese Journal of Atmospheric Sciences
基金
国家重点基础研究发展计划项目2009CB421505
中国气象科学研究院灾害天气国家重点实验室开放课题2009LASW-B01
国家自然科学基金资助项目40875032
40875002
科技部/财政部公益性行业(气象)科研专项GYHY200906004
关键词
热力切变平流参数
对流涡度矢量
水平散度
广义位温
thermodynamic shear advection
convective vorticity vector
horizontal divergence
generalized potential temperature
