Analysis of a Strong Sandstorm in Urumqi

By using of the data of environment monitor,meteorological observation,upper and lower air circulation and satellite remote sensing images,this paper analyzed systematically the synoptic background of strong sandstorm weather in Urumqi in Apr.19th,2004.The results showed that this weather process caused the heavy sand disaster along Tianshan Mountain of northern Xinjiang at 88°E zone,and the concentration of inhalable particulate matter in Urumqi city rose rapidly from 0.79 mg/m3 became 10.0 mg/m3 at the sandstorm weather occurred and API rose to 500 which belong to the severe pollution.During this sandstorm event,air temperature,ground temperature,air pressure,wind speed and visibility of Urumqi city was greatly changed,the gale duration was longer and the visibility was very low.The visibility in some area outside Urumqi city reduced to lower visibility level of heavy sandstorm.According to the analysis of satellite cloud image,upper and lower air circulation and physical quantities,the main factor caused this strong sandstorm weather to be cold front passage.The startup factors were the scheme with the prefrontal uplifting process,the low-level air convergence and the upper level air divergence,and the main driving force of this sandstorm weather was the stronger northwest wind in the rear of cold front with longer duration.