烏魯木齊一次極端暴雪事件中尺度分析
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科技部公益性行業科研專項(GYHY201506009)、國家自然科學基金項目(41565003)共同資助


Mesoscale Analysis of an Extreme Blizzard in Urumqi
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    摘要:

    利用常規資料、NCEP/GFS(0.5°×0.5°)再分析資料,結合EC細網格(0.25°×0.25°) 客觀分析及烏魯木齊風廓線雷達等資料,分析了烏魯木齊2014年12月8日極端暴雪中尺度成因及演變特點。結果表明:暴雪是在低空西北急流與中高層西南急流疊加并維持的有利環流背景下,由700 hPa至地面的風切變、風速輻合、地面冷鋒及地形強迫抬升等中小尺度系統共同作用造成的。降雪前期烏魯木齊近地層有較強的逆溫、風場擾動及低層東南急流,干暖蓋起到了儲蓄和積累能量的作用,而強降雪時冷暖空氣在山前交匯,促進了斜壓不穩定增長。低空西北急流對烏魯木齊強降雪起到動力觸發作用,地形強迫抬升使迎風坡維持強的垂直上升運動和中β尺度次級環流圈,低層強水汽輻合的維持為暴雪提供了充足的水汽,烏魯木齊特殊地形對暴雪增幅作用明顯。風廓線雷達資料表明降雪前后低層東南風與西北風切變明顯,強降雪時段雷達探測高度達到最高,低層較強偏北風與C2n大值區相對應,水平風向風速的垂直變化對暴雪短臨預報有很好的參考價值。

    Abstract:

    Using the data of conventional observation and NCEP/GFS (0.5°×0.5°), in combination with objective analysis of EC finemesh (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 lowlevel jet and the southern west highlevel jet, the blizzard was produced by the interaction of meso and smallscale 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 lowlevel 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 lowlevel jet dynamically worked as a dynamic trigger in the snowstorm. The surface orographic uplift helps maintain the strongly ascending motion and mesoscaleβ secondary circulations. Also, the maintenance of the powerful lowlevel 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 lowlevel layer before and after the snow, the sounding height reached the highest, and the stronger northerly lowlevel wind corresponded to the high value of C2n when snowing heavily. For the shortterm forecast of the blizzard, the horizontal wind and C2n have great reference value.

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張云惠,于碧馨,譚艷梅,劉晶.烏魯木齊一次極端暴雪事件中尺度分析[J].氣象科技,2016,44(3):430~438

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  • 收稿日期:2015-06-12
  • 定稿日期:2015-11-03
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  • 在線發布日期: 2016-06-23
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