云南及周边地区闪电活动和其他干扰因素对NO2的协同影响

Synergistic Effects of Lightning Activity and Other Disturbance Factors on NO2 in Yunnan and Its Surrounding Areas

摘要:

以2018年9月至2022年8月为研究时段，采用多种统计方法对滇西南及周边生物质燃烧高发区（A区）、滇中人类活动强度较大的城市群区（B区）2—4月和6—8月闪电活动及其他干扰因素对NO₂的影响进行对比分析。结果表明：①2—4月A、B区NO₂柱浓度分别与火点数和人为CO₂排放在空间上存在显著正相关，但与闪电次数呈显著负相关。②闪电活动多伴有明显降雨（R≥1 mm），闪电活动较弱时，降雨对地面NO₂的湿沉降作用明显，较强的闪电活动下降雨的湿沉降仍无法完全抵消闪电对地面NO₂浓度增长的贡献。③6—8月初次出现闪电时A、B区地面NO₂浓度前6 h逐时增加，之后3 h则逐时缓慢减小。④闪电日A、B区地面NO₂浓度整体高于无闪电日，生物质燃烧强度、降雨强度和大气边界层高度等变化均会对其产生明显影响。

Abstract:

NO₂ is the common precursor of the secondary conversion of PM_2.5 and O₃. Understanding its change characteristics and influencing factors is of great significance for the collaborative treatment of PM_2.5 and O₃. Based on the VLF/LF three-dimensional lightning location monitoring system, SNPP/VIIRS satellite fire point data, NO₂ column density in Sentinel-5P NRTI NO₂ data products and other data, using various statistical methods, selecting February to April with high NO₂ density and June to August with frequent lightning activities, this paper compares and analyses the influence of lightning activities on NO₂ density in region A (96.5°-102°E, 20.5°-24°N) with high biomass burning in southwest Yunnan and its surrounding areas and region B (102°-104°E, 24°-26°N) with high human activities in central Yunnan. The results show that: (1) There are obvious differences in the spatial and temporal distribution of the number of lightning and NO₂ column density in region A and region B. The NO₂ column density outside area A is higher than that in China, but the distribution of lightning times is the opposite. The NO₂ column density in region B decreases from Kunming to the surrounding area, and the number of lightning is less and more. In the dry season (November to April of the next year), the concentration of NO₂ density is higher, and the rainy season (May to October) is lower, and the number of lightning is opposite. (2) From February to April, the NO₂ column density in region A and region B has a significant positive spatial correlation with the number of fire points and anthropogenic CO₂ emissions, respectively, but a significant negative correlation with the number of lightning. (3) Lightning activity is mostly accompanied by obvious rainfall (R≥1 mm). When the lightning activity is weak, the wet deposition effect of rainfall on the ground NO₂ density is obvious, and the wet deposition effect of rain falling from the stronger lightning activity cannot completely offset the contribution of lightning to the increase of ground NO₂ density. (4) The change of surface NO₂ density during the first lightning from June to August is more regular than that from February to April, which shows that the ground NO₂ density increases hourly in the first 6 hours and decreases slowly hourly in the last 3 hours. (5) The ground NO₂ density on the lightning days in the two regions is generally higher than those on the days without lightning. Changes in biomass combustion intensity, rainfall intensity and planetary boundary layer height have a significant impact on the ground NO₂ density.