Subjects: Geosciences >> Atmospheric Sciences submitted time 2023-05-30 Cooperative journals: 《干旱区研究》
Abstract： To quantitatively evaluate the effect of meteorological conditions on air pollution, data from 14 meteorological sounding stations and surface observation stations in Xinjiang were used to analyze the spatial and temporal distribution characteristics of atmospheric self-purification capacity index (ASI) and air stagnation index (ASITS) from 2010 to 2020. Results showed a negative correlation between ASI and ASITS. ASI was the largest in summer and the smallest in winter. It was generally greater in southern Xinjiang than in northern Xinjiang, whereas ASITS showed the opposite trend. This implied that the atmospheric diffusion conditions were better in southern Xinjiang than in northern Xinjiang, and a static and stable atmospheric circulation more easily formed in northern Xinjiang than in southern Xinjiang. The daily pollution data of air environment monitoring stations from 2015 to 2020 were used to determine the correlation between the air quality of Xinjiang in different seasons and the air quality of five heavily polluted stations and the two indexes. The two indexes highly correlated with the air pollution data of Urumqi station, and the static stability index was better, which can well indicate the degree of air pollution. However, no good correlation was found between the two indexes and the air pollution data of four stations in the southern Xinjiang basin. In the heavy pollution case in the spring of 2018, the PM10 concentration span was very large, so the two indexes showed a high dispersion on the scatter diagram, which is not applicable. In particular, in Hotan and Aksu, the two indexes showed a certain correlation with the pollutant concentration, and ASITS performed better. In Kashgar, ASI showed no correlation with air quality, and ASITS showed a weak correlation; the two indexes showed no correlation with the air quality of Korla, implying poor applicability. Further study on the distribution of indexes under different pollution levels in the capital city of Urumqi showed that the early warning indicators can be preliminarily condensed as follows: When pollutant emission is serious, and if ASI is distributed at 0-20 t·(d·km2)−1, it is susceptible to heavy weather pollution, and the range of ASITS is of little significance.
Subjects: Geosciences >> Atmospheric Sciences submitted time 2022-01-21 Cooperative journals: 《干旱区地理》
Abstract：利用20102019年新疆14个探空气象站资料统计分析了近10 a大气最大混合层高度（下文简称混合层高度）、通风量、边界层平均风速及大气自净能力指数的时空分布特征，探讨了各物理参数与空气质量的关系。结果表明：（1）以上参数的逐月分布均呈倒V型，表现为夏半年大、冬半年小，即新疆的大气扩散能力在夏季最强、冬季最弱，其中混合层高度和通风量在冬、夏季差距悬殊。（2）南疆大气扩散能力普遍比北疆好，无论冬夏南疆的自净能力、通风量、混合层高度均大于北疆。（3）北疆除阿勒泰站外，其余站点上述物理参数均与空气质量指数（Air quality index，AQI）呈显著负相关，即大气扩散能力越强，空气质量越好，而南疆只有和田站通过了0.01的置信度检验，但两者呈正相关，即大气扩散能力越强，空气质量越差，这归因于南北疆不同的大气污染来源。
Subjects: Geosciences >> Geography submitted time 2019-11-15 Cooperative journals: 《干旱区地理》
Abstract：东南大风是乌鲁木齐城区独有的强灾害性天气，通过研究发现东南大风是天山峡谷特殊地形造成的大振幅重力波与超低空急流耦合触发的强下坡风暴。针对2012年3月30日乌鲁木齐城区出现的近10 a最强的一次东南大风天气过程，使用中尺度WRF模式进行数值模拟，分析模式输出的高时空分辨率产品发现：在气压梯度力作用下，气流从天山峡谷南端进入，一方面由于狭管效应在峡谷内300~400 m高度形成超低空急流；另一方面气流在进入峡谷过程中，因爬坡强迫抬升形成重力波。重力波在峡谷内与超低空急流发生耦合，在峡谷北端背风坡形成大曲率背风波，背风波的下沉运动引起动量下传，将超低空急流的能量输送到地面，形成水跃型下坡风暴即东南大风。在此过程中背风坡上空风向切变的临界层吸收上层波能量加强了超低空急流，对流层低层稳定层结对背风波的下沉运动起到加速作用。
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