ANALYSIS OF DIFFUSION CHARACTERISTICS AND FORMATION CAUSES OF PM2.5 IN SHENYANG USING WRF-CHEM
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摘要: 日益严峻的城市大气环境质量不仅与当地污染物大量排放有关,还受到区域传输的影响。以沈阳市2017年1月一次大气污染过程为研究对象,利用WRF-HYSPLIT模式计算后向轨迹,结合WRF-Chem空气质量模型模拟地表PM2.5颗粒物的扩散过程,同时分析了区域内的地面、高空天气系统特征。研究结果表明,2017年1月的气团轨迹传输模式可分为5类:偏西方向的传输模式1移动速度快,发生频率和污染浓度均最低,第2、3类簇团在传输模式上相近;均起源于内蒙古自治区内,向东南方向移动至目标区域,轨迹PM2.5浓度均值较低依次为45.47,67.97 μg/m3,频率依次为24.19%、15.32%;第4类簇团传输模式为本地输送,轨迹占比为33.06%且污染水平最大(121.66 μg/m3);西南方向传输模式5的频率占比为14.53%,PM2.5污染水平为105.5 μg/m3。通过轨迹计算与空气质量模型结果对比发现,西南方向的传输模式与东北方向的传输模式会导致目标区域PM2.5浓度升高,地形动力因子和热力因子所形成的东北地形槽和长白山小高压,更易导致重污染事件。Abstract: In recent years, the quality of the atmospheric environment in many cities has become increasingly severe, which is not only related to the emission of pollutants from local sources, but also affected by regional transportation. Taking an air pollution process as an example in Shenyang, Liaoning in January 2017, the evolution process and meteorological impact were analyzed. Firstly, the WRF-HYSPLIT model was used to calculate the backward trajectories, and the WRF-Chem air quality model was used to calculate the ground surface PM2.5 particle diffusion process. At the same time, the surface synoptic map and isobaric surface in the study area was analyzed and simulated. The results showed that the air mass trajectory pathways in January 2017 could be divided into 5 types, in which the trajectory cluster 1 in the west direction had the fastest moving speed, but the pollution value and frequency were lower. And the transport pathways numbered 2 and 3 were similar originating in the Inner Mongolia Autonomous Region and moving to the southeast direction to the target area. And these trajectories carried low PM2.5 value of 45.47, 67.97 μg/m3, with frequency of 24.19% and 15.32%, respectively. The cluster 4 showed that the local source transports accounted for 33.03% with the largest pollution level, which was 121.66 μg/m3. The trajectory cluster 5 in the southwest transport pathway had a frequency of 14.53% and the PM2.5 value of 105.5 μg/m3. The results of air quality model were consistent with the trajectories calculation results:the southwest and the northeast transport pathways led to a particulate matter increase in the target area. Heavy pollution events were more likely to occur due to the impact of Northeast China Topographic Trough and Changbai Mountain Small High Pressure formed by topographical dynamics and thermal factors.
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Key words:
- HYSPLIT /
- K-mean algorithm /
- main transport pathways /
- WRF-Chem /
- Shenyang
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