冷锋型和蒙古气旋型沙尘天气过程典型个例对比分析

利用观测资料和NCEP再分析资料,对冷锋型和蒙古气旋型两类沙尘天气过程的典型个例进行对比分析。结果表明:斜压强迫在两类过程中均较为显著,冷锋型沙尘天气过程中,随高度降低高空槽明显加深;蒙古气旋型则在对流层低层（850 hPa）、中层（500 hPa）形成切断低压。冷锋型沙尘天气过程高空锋区位置较蒙古气旋型偏南,且南压更为明显;冷锋型沙尘天气过程沙尘天气区位置也较蒙古气旋型偏南,且主要向东南方向扩展。冷锋型地面高、低压强度对比明显大于蒙古气旋型,且地面风速与能见度的反相关性高于蒙古气旋型,锋后降温也较蒙古气旋型显著。冷锋型锋前上升运动中心位于700 hPa,锋后下沉运动中心位于600 hPa。蒙古气旋型气旋中心及其附近300 hPa以下均有强的上升运动。冷锋型锋面附近正涡度随高度增高而增大,蒙古气旋型气旋中心及其附近为正涡度。最后给出了冷锋型和蒙古气旋型沙尘天气过程的天气学概念模型。

A Comparative Analysis on the Typical Cases of the Cold Front and Mongolia Cyclone Dust Storms

By using meteorological observation data and NCEP reanalysis data, a comparison between a cold front dust storm and a Mongolia cyclone dust storm were conducted. The results showed that there was evident baroclinic forcing in both kinds of dust storm processes. For the cold front process, the upper-level trough deepened according with the height decreased. For Mongolia cyclone process, there was cut off low appeared at low level (850 hPa) and middle level (500 hPa) of troposphere. The upper level frontal zone in the cold front process appeared more southern than that in the Mongolia cyclone process. Further more, it also expanded southward much more. Similarly, the dust storm weather areas in the cold front process appeared more southern than that in the Mongolia cyclone process. And it expanded southeastwards mainly. The difference of central pressure between the surface high and low in the cold front process larger than in the Mongolia cyclone process. The anti-correlation between surface wind speed and surface visibility in the cold front process is higher than in the Mongolia cyclone process. The post-frontal temperature in the cold front process decreased more evidently than in the Mongolia cyclone process. The maximal values of ascending motion behind and before the cold front in the cold front process were at 700 hPa and 600 hPa, respectively. In the Mongolia cyclone process it expanded from surface to 300 hPa nearby the cyclone region. In the cold front process, the positive vorticity near the cold front increased according with the height increased. In the Mongolia cyclone process, the positive vorticity was located at the cyclone areas. Finally, the weather conceptual models of cold-front and Mongolia cyclone dust storm were summarized.