冀南地区一次强对流型强沙尘暴成因分析

利用常规观测资料、卫星云图、雷达及NECP等资料对2005年5月10日冀南地区强沙尘暴天气过程进行分析,探讨了这次强对流型沙尘天气的成因。结果表明,上冷下暖的垂直结构和午后地面受热增温,容易产生热对流不稳定;地面大风的形成主要源于冷锋前的飑线,雷达回波图上表现为典型的弓状回波,地面中尺度辐合线对飑线发生有重要的作用,高空急流的加强及其形成的次级环流使高空动量有效的下传到地面则是另一个重要原因;沙尘暴区位于高低空急流交汇的区域,700hPa螺旋度正值与高能舌重合区和高空300hPa螺旋度正值区梯度较大的地区,对流层螺旋度大小对沙尘暴预报有一定的指示意义。

Causality Analysis of a Strong Convective Severe Sand-dust Storm in the South of Hebei Province

Using conventional observational data ,satellite images, Dopper radar echo and NECP data, the causality of the strong convective severe sand-dust storm in the south of Hebei on May 10,2005 is discussed. The results show that the vertical structure of cold advection in the upper air and the warm advection in the lower level, and increasing temperature at afternoon provided the advantageous thermal condition. Strong surface winds were mainly caused by a squall line ahead of the cold front which showed as a arc echo, the surface mesoscale convergence line is very important to the squall line. Meanwhile, the development of upper-level jet and strong downward transport of momentum by the sinking branch of the upper level jet's secondary circulation are also important for the formation of strong surface winds. The dust devil occurred at the coupled area of high/low level jets and the superposition of the positive helicity value at 700hPa and high-energy tongue and the higher gradient of the helicity's positive value at 300hPa, the magnitude of the tropospheric helicity is useful for the prediction of dust devil events.