2015~2021年青藏高原地表臭氧时空变化及驱动因素分析

Spatial-temporal Variations and Driving Factors of Surface Ozone over the Qinghai-Xizang Plateau from 2015 to 2021

基于青藏高原12个城市2015~2021年的大气污染监测数据和气象数据,分析了青藏高原地表臭氧(O_(3))时空分布格局.采用KZ滤波将O_(3)-8h原始序列分解为不同时间尺度的分量,并利用气象变量的多元线性回归定量地分离出气象和排放的影响.结果表明,2015~2021年青藏高原12个城市地表ρ(O_(3)-8h)均值为78.7~156.7μg·m^(-3),O_(3)浓度超标率(国家二级标准)为0.7%~1.5%.O_(3)-8h月浓度变化呈单峰倒“V”型和多峰“M”型,浓度峰值出现在4~7月,谷值多出现在7月、9月和12月.经KZ滤波分解的O_(3)-8h短期、季节和长期分量对12个城市O_(3)-8h原始序列总方差的贡献率分别为29.6%、51.4%和9.1%.从整个区域看,2015~2017年气象条件对青藏高原O_(3)降低不利,使得O_(3)-8h长期分量升高0.2~2.1μg·m^(-3).2018~2021年气象有利于O_(3)浓度降低,导致O_(3)-8h长期分量降低0.4~1.1μg·m^(-3).气象条件增加了阿里、拉萨、那曲、林芝、昌都、海西和西宁的O_(3)-8h长期分量,其平均贡献率为30.1%.气象条件降低了日喀则和果洛的O_(3)-8h长期分量,贡献率分别为359.0%和56.5%.阿里、日喀则、那曲、海西和西宁O_(3)-8h长期分量的上升可能是由于PM_(2.5)长期分量快速下降[4.04μg·(m^(3)·a)-1]导致.

The spatial-temporal distribution pattern of surface O_(3) over the Qinghai-Xizang Plateau(QXP)was analyzed based on air quality monitoring data and meteorological data from 12 cities on the QXP from 2015 to 2021.Kolmogorov-Zurbenko(KZ)filtering was employed to separate the original O_(3)-8h series into components at different time scales.Then,multiple linear regression of meteorological variables was used to quantitatively isolate the effects of meteorology and emissions.The results revealed that the annual mass concentrations of surface O_(3)-8h from 2015 to 2021 in 12 cities over the QXP ranged from 78.7 to 156.7μg·m^(-3),and the exceedance rates of O_(3) mass concentrations(National Air Quality Standard of grade II)ranged from 0.7%-1.5%.The monthly O_(3)-8h mass concentration displayed a single-peak inverted“V”-shape and a multi-peak“M”-shape.The maximum monthly concentration of O_(3) occurred in April to July,and valleys occurred in July,September,and December.The short-term,seasonal,and long-term components of O_(3)-8h decomposed by KZ filtering contributed 29.6%,51.4%,and 9.1%to the total variance in the original O_(3) sequence in 12 cities,respectively.From the whole region,the meteorological conditions were unfavorable for O_(3) reduction on the QXP from 2015 to 2017,which made the long-term component of O_(3) increase by 0.2-2.1μg·m^(-3).The meteorological conditions were favorable for O_(3)-8h reduction from 2018 to 2021,which led to the long-term component of O_(3)-8h decrease by 0.4-1.1μg·m^(-3).The meteorological conditions increased the long-term component of O_(3)-8h in Ngari,Lhasa,Naqu,Nyingchi,Qamdo,Haixi,and Xining,with an average contribution of 30.1%.The meteorological conditions decreased the long-term component of O_(3)-8h in Shigatse and Golog,with contributions of 359.0%and 56.5%,respectively.The increase in the long-term component of O_(3)-8h in Ngari,Shigatse,Nagqu,Haixi,and Xining could be due to the rapid decrease in the long-term component of PM_(2.5)(4.04μg·(m^(3)·a)−1).