Mesoscale Analysis of an Extreme Blizzard in Urumqi
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Abstract:
Using the data of conventional observation and NCEP/GFS (0.5°×0.5°), in combination with objective analysis of EC finemesh (0.25°×0.25°) data and the wind profile radar data of Urumqi, the mesoscale causes and the evolution characteristics of the extreme blizzard on 8 December 2014 in Urumqi are analyzed. The results show that under the background of superposing and maintaining of the northwestern lowlevel jet and the southern west highlevel jet, the blizzard was produced by the interaction of meso and smallscale systems such as the shear and convergence system of the wind from 700 hPa to the surface, surface cold front, orographic uplift, and so on. There were significant inversion, wind disturbance, and the southeast lowlevel jet in the surface layer over Urumqi before the snow. The warm dry lid played a role of storing and accumulating energy. While snowing, the cold and warm air met in front of the mountains, prompting the increase of baroclinic instability. The northwest lowlevel jet dynamically worked as a dynamic trigger in the snowstorm. The surface orographic uplift helps maintain the strongly ascending motion and mesoscaleβ secondary circulations. Also, the maintenance of the powerful lowlevel water vapor convergence provided sufficient water vapor for the blizzard. Meanwhile, the special orography of Urumqi obviously contributed to the blizzard growth. On the wind profile radar, there was a clear shear of the southeast and northwest winds in the lowlevel layer before and after the snow, the sounding height reached the highest, and the stronger northerly lowlevel wind corresponded to the high value of C2n when snowing heavily. For the shortterm forecast of the blizzard, the horizontal wind and C2n have great reference value.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.