A Comparative Analysis of Two Snowstorms in Shandong Province
By using conventional weather chart data, sounding data, densified automatic weather station (AWS) data, ground based GPS/MET remote sensing observation data of atmospheric water vapor, satellite cloud images, Doppler radar observations and the NCEP/NCAR 1°×1° reanalysis data, the water vapor, thermal and dynamic conditions and the mesoscale characteristics of two snow storms in Shandong Province during 11 to 12 November in 2009 and 28 February in 2010 were comparatively analyzed by using diagnostic methods. The results have shown: (1) The two snowstorms were caused by upper level trough. There were warm and weter advection transported by stronger southwesterly flow at about 700 hPa. All atmospheric levels were near saturated. There were inversion temperatures in the middle low level. The all level temperatures were less than 0℃. The snowstorm occurred in the front of southwest airflow in the 700-500 hPa trough and the converged region of the northeasterly and southeasterly at 850 hPa. Northeasterly winds were prevailing in the surface layer. (2) There were different characters in the two snowstorms. In the November 2009 snowstorm, there was the cold air influenced firstly then the warm and wet airflows run into middle high levels, thus lower energy was stored in low levels, forming a stable heavy snow with longer duration. But in the February 2010 snowstorm, the warm and wet airflows inflowed firstly, then the cold air run into low levels. The vortex formed in low levels and cyclone came into being in the surface.There was convective instability in middle low levels so that convection developed, a snowstorm with great snowfall intensity and short duration occurred. (3) In two snowstorms, the GPS/ MET precipitable water vapor were observations all about 20 mm, which can be an indicator for snowfall amount. The 0℃ isolines of the temperatures observed by densified AWS were the boundary between rains and snows, which can help distinguish the precipitation forms.