科研之友
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摘要
Based on wind profiles obtained from Scanning Lidar, the characteristics of wind field from 1 December 2017 to 28 February 2018 in Lanzhou were analyzed. Through the cluster analysis, the weather types affecting Lanzhou area in winter was obtained. The characteristics of wind field under different weather types and the diurnal variation characteristic were analyzed. The results show that, winter low-level wind speed during the study period were very low, and were dominated by easterly wind. The diurnal variation of wind field was obvious, with higher wind speed from the afternoon to the evening than during other times. There was westerly wind at the height between 250 m and 700 m from night to the next morning, while easterly wind prevailed the rest of time below 800 m. In addition, local circulation was dominant when the study area was controlled by weak high-pressure, and the related low wind and strong downdraft led to serious pollution. The wind direction with the maximum air pollution index was different at each height and the pollution index decreased rapidly above 200 m. Increase the emission height of pollutants above 200 m can effectively reduce the concentration of near-surface pollutants.
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