“07.3”强沙尘暴天气过程的观测分析

Observation and analysis of“07.3”severe sandstorm

利用常规观测的地面资料、探空资料、卫星云图资料、客观分析资料以及民勤站和SACOL站的观测资料对2007年3月27-28日中国西北地区的一次强沙尘暴过程进行了分析.主要结论为:地面快速发展的冷锋以及850 hPa和700 hPa快速发展的短波槽与此次沙尘暴的形成和快速发展密切相关.民勤站沙尘浓度和地面气象要素在沙尘暴发展演化期间出现明显的变化.气压和风速在沙尘暴爆发时出现明显的跃升,气压的变化超前于风速的变化,这表明风场和气压场在沙尘暴爆发时有明显的调整过程;风速及其垂直切变与PM_(10)浓度几乎同时达到极大值,而温度垂直切变极大值出现时刻比PM_(10)浓度和风速垂直切变极大值早出现4h;强的风速垂直切变有利于激发不稳定能量的释放和沙尘暴的形成.SACOL站的沙尘浓度和地面气象要素在沙尘暴发展期间也有明显的变化.风速和气压达到峰值的时刻都超前于PM_(10)浓度出现极大值的时刻;温度垂直切变峰值出现的时刻稍稍滞后于风速垂直切变峰值出现的时刻.

The sandstorm that occurred on 27-28 March, 2007 in the northwest of China was analyzed with observed data from the Minqin station and the Semi-Arid Climate and Environment Observatory of Lanzhou University （SACOL）, and also with weather reports, objectively analyzed data and satellite images. The main results are： Synoptic analyses of the sandstorm indicate that a quick development of the short wave trough at 700 hPa and 850 hPa associated with surface cold front contributed to the formation and development of thesandstorm. Observed data at the Minqin station show that the mass concentration of PM10, pressure and wind speed at ground levels underwent obvious variation during the sandstorm＇s development. The pressure and wind speed had a jump when the sandstorm broke out and the variation of pressure was ahead of the wind speed, which means that the adjustment between the wind field and pressure field was obvious when the sandstorm broke out. The vertical shear of wind speed and concentration of PM10 reached their peaks simultaneously.However, the peak of the verticM shear of temperature was ahead of the peak of mass concentration of PM10 and wind speed. The strong wind speed favored the emission of dust and, at the same time, the strong vertical shear of wind speed favored the release of instable energy and the formation of the sandstorm. Observed data at SACOL show that the mass concentration of PM10, pressure and wind speed at ground levds underwent obvious variation during the development of the sandstorm. Wind speed and pressure at SACOL reached their peaks ahead of the mass concentration of PM10. The vertical shear of temperature reached its peak ahead of the mass concentration of PM10 and lagged behind the vertical shear of wind speed.