【摘要】 夏季沙尘暴的气候特征表明,夏季是甘肃省沙尘暴的次多发季节,主要集中在民勤、鼎新、金塔。通过对一次罕见的甘肃省夏季强沙尘暴天气分析发现:高空小槽、切变线、热低压是引发夏季沙尘暴的主要天气系统,而春季沙尘暴一般是大尺度天气系统造成的;夏季沙尘暴发生前期高空急流反映并不明显,急流风速的突然加大和沙尘暴几乎同时发生,这是夏季沙尘暴预报的难点之一;沙尘暴发生前8~12 h的螺旋度场对沙尘暴预报有较好的指示意义,正值越大,沙尘暴越强,但当沙尘暴与强降水同时发生时,沙尘暴区螺旋度值明显小于强降水中心螺旋度值。更多还原

【Abstract】 Sand-dust storms in Gansu Province occurred most frequently in summer. The summer sand-dust storms concentrated around Minqin,Dingxin and Jinta.The weather patterns for severe sand-dust storms in summer in Gansu Province are analyzed.The results show that upper troughs and shear lines and hot lows are main synoptic systems that result in summer sand-dust storms.Spring sand-dust storms are mostly induced by large-scale synoptic systems.Before the occurrence of summer sand-dust storms,the upper-level jet currents are not apparent.The sudden wind speed increase of the jet stream happens almost at the same time with a sand-dust storm,and that is one of difficulties in summer sand-dust storm prediction.The helicity field 8 to 12 hours before sand-dust storm occurring is a good indicator in forecasting sand-dust storms.The larger the helicity is,the severer the sand-dust storm is.But when a sand-dust storm and severe precipitation occur concurrently,the value of helicity in the sand-dust storm region is obviously less than that in the severe precipitation region.更多还原