Diagnosis of a Sandstorm Weather Event in the South of Junggar Basin

Based on the data of basic observation and numerical forecasting product T639,the causes of a sandstorm weather process occurred on April 13,2009 in the south of Junggar Basin were analyzed.The results show it was caused by the north-west strong cold air.The continual temperature rising provided the favorable thermal condition for sandstorm,and the West Siberian cold trough moving towards southeast and developing greatly provided the dynamical condition for it.The vertical structure of Siberian cold trough provided the mechanism of momentum transmitting downwards for sandstorm.The upper and lower level jet stream made the frontal zone at the middle and lower troposphere strengthen and atmospheric stratification unstable,which provided a favorable large-scale circulation environment.The development and persistence of dry-warmer tongue was an omen for its occurrence.The strong sandstorm occurred in the rear of the cold front,the front of the cold high pressure and the airflow divergence zone.Moreover,the special terrain also provided a favorable geographical condition.