基于小波分析的PM2.5分布特征及差异分析

为了解西北内陆和东部沿海PM_2.5浓度值特征和差异，使用小波分析和Spearman相关性分析对12个主要城市冬、春季PM_2.5浓度值进行分布特征和差异对比分析。结果表明:受地理位置和地形差异影响，PM_2.5浓度值在西北内陆和东部沿海城市有明显差异性。主要表现在:1）冬、春季西北内陆和东部沿海地区PM_2.5分布存在明显差异，东部沿海空气质量优于西北内陆，PM_2.5超标率相对较低，而乌鲁木齐和西安PM_2.5超标占比较高；2）小波分析显示，西北内陆和东部沿海在周期上表现出明显区别，但整体出现在冬季（80 d之前）；3）Spearman相关系数存在明显的距离衰减性，相关系数由西北内陆向东部沿海城市依次减弱；4）东部和西北PM_2.5浓度值突变在时间尺度上有较明显差异，西北内陆突变值整体出现在第2，11，24，49，70天，东部沿海则出现在第2，17，42，53，70天。

DISTRIBUTION CHARACTERISTICS AND DIFFERENCE ANALYSIS OF PM2.5 BASED ON WAVELET ANALYSIS

To understand the characteristics and differences of PM_2.5 concentration in the northwest inland and east coast, this paper used wavelet analysis and Spearman correlation analysis to compare the distribution characteristics and differences of PM_2.5 concentration values in 12 major cities in winter and spring. The results showed that, affected by differences in geographic location and topography, the concentration of PM_2.5 was significantly different in the northwest inland and east coastal cities. The results mainly manifested in:1) the distribution of PM_2.5 in the northwest inland and the eastern coastal areas was significantly different in winter and spring. The east Coastal areas were better than the northwest inland areas, while the east coastal areas had relatively low excess rates. Urumqi and Xi'an accounted for a relatively high percentage of excesses; 2) Wavelet analysis showed that the northwest inland and the east coast possessed obvious differences in cycle, but the overall appearance occurred in winter (before 80 d); 3) The Spearman correlation coefficient had obvious distance attenuation, and the correlation coefficient weakened from the northwest inland to the coastal cities in the east; 4) The abrupt changes of PM_2.5 concentration values in the east and northwest were significantly different on time scales. The overall abrupt changes in the northwestern inland areas appeared on the 2nd, 11th, 24th, 49th, and 70th day, and the eastern coastal areas appear on 2nd, 17th, 42th, 53th, 70th day.