The results show that uppertrough and shear line and thermal depression are main synoptic systems introducing summer sand-dust storm.
研究发现高空小槽、切变线、热低压是引发夏季沙尘暴的主要天气系统。
2
The squall line is a kind of instable and strong convective weather caused by the air with upper-layer dry and lower-layer wet in front of the upper-troposphere trough.
分析指出，该飑线系统是由高空槽前型的上干下湿引起的不稳定强对流天气。
3
The major systems come from the shear line of low-layer, the low trough of upper air and the ground stationary front.