基于探空数据的新疆大气扩散条件时空分布特征分析

Spatial and temporal characteristics of atmospheric diffusion conditions in Xinjiang based on radiosonde data

利用2010—2019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。

On the basis of data from 14 radiosonde stations and their corresponding surface meteorological automatic observation stations in Xinjiang,China,from 2010 to 2019,the temporal and spatial distribution characteristics of air mixing depth,ventilation rate,mean wind speed in boundary layer,and air self-cleaning ability index in the past 10 years were analyzed.The correlation between meteorological parameters and air quality was discussed based on the air quality index(AQI)data of 10 air quality monitoring stations in Xinjiang from 2015 to 2019.Results show that(1)the monthly distributions of the maximum mixing depth,the ventilation rate,the mean wind speed in the boundary layer,and the index of atmospheric self-cleaning ability had an inverted“V”shape,thereby indicating that the atmospheric diffusion ability of Xinjiang is strong in summer and weak in winter.(2)With regard to the spatial distribution of atmospheric diffusion conditions in Xinjiang,two different diffusion areas are found in southern and northern Xinjiang due to different topographies.The atmospheric diffusion conditions in southern Xinjiang are generally better than those in northern Xinjiang.Whether in winter or summer,southern Xinjiang has greater self-cleaning ability,ventilation capacity,and mixing depth than northern Xinjiang does,but the mean wind speed in the boundary layer is the same in southern and northern Xinjiang.This condition is mainly due to the great difference of non-adiabatic heating on the ground caused by different sunshine duration and intensity.(3)An analysis of the correlation between the above parameters and AQI shows that the atmospheric diffusion conditions of stations in northern Xinjiang are significantly negatively correlated with AQI except Altay station,and they all passed the 0.01 confidence test.The conditions are not consistent in southern Xinjiang;only Hotan station passed the 0.01 confidence test,thus indicating a significantly positive correlation,which is the opposite of northern stations in Xinjiang.This result occurred because the causes of air pollution in northern and southern Xinjiang are different.The main pollution sources in southern Xinjiang during spring are sand and dust,especially at Hotan statio station,where sand and dust increase under good atmospheric diffusion conditions,resulting in poor air quality.In northern Xinjiang,pollution is mostly due to the stable atmospheric stratification,which results in failed coal smoke emission from urban factories.The strong atmospheric diffusion ability will help the dilution and diffusion of pollutants and improve the air quality.