摘要
垂直螺旋度Hp由垂直速度和垂直涡度构成,反映涡度的垂直平流。通过尝试将Q矢量引入垂直螺旋度进行研究,即基于Q矢量散度和垂直涡度构造出一种新型垂直螺旋度HQ。HQ为Hp的拓展形式,二者差别主要在于计算HQ时无需求解垂直速度。同时,结合一次典型的江淮梅雨锋气旋暴雨过程研究,结果表明,HQ对降水落区及降水强度水平分布的不均匀性均具有较好的反映能力,且揭示出暴雨上空垂直涡度平流呈倾斜分布特征。进一步分析表明,对于垂直涡度而言,HQ三维空间分布特征与辐合的Q矢量散度有更多的相似性,这在一定程度上反映出HQ与Q矢量散度联系更为密切。
Vertical helicity( termed as Hp) consists of vertical velocity and vertical vorticity,reflecting vertical advection of vorticity. Until now,vertical velocity can't be obtained directly by observations,which leads to calculate vertical helicity inconveniently. It is well known that Q vector is taken as an advanced tool for diagnosing vertical motion,and when vertical velocity in atmosphere has wave-like feature,there is proportional relationship of divergence of Q vector and vertical velocity,i. e.,·Q∝ω( ω is vertical velocity in p-coordinate),in other words,the divergence of Q vector can estimate vertical motion indirectly. The Q vector is drawn into study on helicity first time in this paper,specifically,a new type of vertical helicity( termed as HQ) is constructed on the basis of Q vector divergence and vertical vorticity. HQ is an extensional form of Hp,and they have the same physical meaning and similar diagnostic feature. The intrinsic difference between HQ and Hpis that the vertical velocity needed not to be given before calculating HQ. On some degree,the genesis of HQ firstly realizes organic fusion of the two advanced tools of helicity and Q vector,meanwhile,the diagnostic ability of HQ will be improved along with the developing of Q vector theory. The application of HQ to a typical Changjiang-Huaihe Meiyu front cyclone torrential rainfall shows that HQ has a good reflecting ability to synchronous precipitation intensity,occurring region and their inhomogeneities,and discloses the characteristics of vertical vorticity advection tilting northwards with height over torrential rainfall area. Further analysis indicates that there is obvious positive vertical vorticity and convergence of Q vector divergence preserving over precipitation area,and there is a good corresponding relationship between convergence region of Q vector divergence and occurring region of precipitation. HQ is the synthetic manifestation of roles from Q vector divergence and vertical vorticity,however,the three dimensions spatial distributional feature of HQ has more similar to counterpart of Q vector divergence with respect to vertical vorticity,which displays HQ relating more closely to Q vector divergence.
出处
《高原气象》
CSCD
北大核心
2014年第5期1281-1288,共8页
Plateau Meteorology
基金
国家自然科学基金项目(40875025
40875030
40775033
41175050)
上海市自然科学基金项目(08ZR1422900)
中国气象局2009年气象新技术推广重点项目(CMATG2009Z01)
公益性行业(气象)科研专项(GYHY201306012)
关键词
垂直螺旋度
Q矢量散度
垂直涡度
梅雨锋气旋暴雨
拓展研究
Vertical helicity
Q vector divergence
Vertical vorticity
Torrential rainfall from Meiyu front cyclone
Extensional study
