河西走廊一次特强沙尘暴的热力动力特征分析

使用NCEP再分析资料、高空和地面观测资料对2010年4月24日发生在河西走廊的一次特强沙尘暴天气进行了热力和动力作用诊断分析。结果表明:沙尘暴发生前,感热通量达最大值,湍流运动增强,增加了大气的不稳定性;大风沙尘暴发展和强盛期与动量通量大值区对应,动量通量对沙尘向上输送起了重要作用;在强锋区附近,地转关系被破坏,大风沙尘暴大气主要出现在变压梯度大,即变压风大的区域,变压风是产生地面强风的主要成分;河西走廊这次沙尘暴过程有明显锋生活动,锋生过程使锋面次级环流加强;水平螺旋度负值中心值越大,近地面层风速越大,大风沙尘暴天气主要出现在水平螺旋度负值中心前方与零值线之间;在河西走廊上空,高空急流沿等熵面穿越等位势高度面下滑到2000gpm,形成偏西风低空急流,低空急流的形成和维持在大风沙尘暴过程中起到关健作用。

Diagnostic Analysis of Thermal and Dynamical Characteristics of a Heavy Dust Storm in Hexi Corridor

By using the (1°×1°) reanalysis data of NCEP and the data of upper air sounding and surface observations, the thermal and dynamical features of a heavy dust storm occurring on 24 April 2010 in the Hexi Corridor are analyzed. The calculated results show that before the dust storm occurs, the sensible heat flux reaching the maximum value increased the atmospheric instability. The gale and dust storm are in accordance with the great value area of the momentum flux, and the momentum flux plays an important role in the transporting upwards dust. Nearby the strong frontal zone, the geostrophic balance is destructed, the dust storm mainly appears in the area of great allobaric gradient and the allobaric wind is the principal constituent of the surface gale. This heavy dust storm is a process of strong frontogenesis and the latter causes the frontal secondary circulation strengthening. The greater the negative (absolute) value of horizontal helicity is, the greater the surface wind speed will be. The gale and dust storm mainly appear between the right front of the horizontal helicity negative value center and zero contour. The upper level jet traversing geopotential height surface along isentropic surface slides down to 2000 gpm and forms the westerly low level jet. The low level jet plays a crucial role in the producing process of the dust storm.