河北省中南部一次沙尘暴的动力条件分析

Analysis on Dynamic Condition of a Sandstorm Process in Central and Southern Hebei Province

利用常规气象观测资料、NCEP 1°×1°再分析资料等,对2005年4月19～20日河北省中南部一次沙尘暴过程的动力条件进行了分析。结果表明,这次沙尘暴过程是在有利的前期气候背景和当时不稳定的大气条件下产生的;变压风在地面大风的形成中起主要作用,地转风风速与变压风风速之和接近地面10 min平均风速值。研究还指出了预报沙尘暴天气的主要着眼点：地面正3 h变压主要由中低层冷平流决定,蒙古气旋发展使补充南下的冷空气在地面产生明显的正3 h变压;当中高层转为偏北气流后,涡度平流随高度减小,高层动量才得以下传,造成500 hPa急流加强,使对流层低层锋生,加大了地面风速。

Dynamic conditions of a sand storm process in central and southern of Hebei Province on April 19~20, 2005 is analyzed using the conventional meteorological observation material, NCEP 1°×1° reanalyzed data and so on. The result shows that this sandstorm process develops under the advantageous preliminary climate background and the unstable atmosphere conditions. The allobaric wind plays the leading role to generate the ground gale, and the sum of geostrophic velocity and isallobaric velocity is close to the 10 minutes mean velocity. The forecast points for the sandstorm obtained by the investigation are as follows： The positive three-hour allobar is mainly decided by the cold temperature advection in lower troposphere, and the Mongolian cyclone＇s development makes the positive three-hour allobar obviously produced by the supplementary cold air from the Lake Baikal. The upper air momentum transfers downwards only when the upper air current changes its direction to northwest and vorticity advection decreases with height, and strengthen the 500 hPa jet stream, which causes the 850 hPa frontogenesis, thus generates ground gale.