大气中一氧化碳浓度变化的模拟研究

Numerical Simulations on the Change of Atmospheric Carbon Monoxide

应用全球二维大气化学模式，模拟了ＣＯ、ＣＨ４和ＯＨ自由基等成分自工业革命到２０２０年的长期变化。模拟的全球ＣＯ平均体积分数在１８４０年、１９９１年和２０２０年分别为２７×１０－６、７６×１０－６和１０５×１０－６。从１８４０到１９９１年，ＯＨ自由基数浓度从７，１７×１０５个分子／ｃｍ３下降到５．７９×１０５个分子／ｃｍ３．降低了 １９％。模拟的ＣＨ４长期变化与冰芯资料相符。模拟的２０世纪８０年代ＣＯ体积分数年增长率为１．０３％～ｌ．０６％。大气中ＣＯ在２０世纪９０年代前是增长的，而到９０年代初观测到ＣＯ体积分数突然下降。应用二维大气化学模式对此原因进行了模拟研究，结果表明，ＣＯ排放源的减少是ＣＯ体积分数下降的主要因子，平流层臭氧减少是另一个重要因子。尽管ＣＯ排放源的减少对大气ＣＨ４增长率的变化有较大影响。

A globally two-dimensional chemistry model is used to study the long-term trends of CO, OH, CH4 from the pre-industrial period to 2020. The calculated globally averaged mixing rate of CO is 27 ×10-9 before l840, 76 × 10-9 in l99l and will reach 105 × 10-9 in 2020. From 1840 to 1991, the averaged tropospheric concentration of OH which changed from 7. 17 ×105 molecule / cm3 to 5.79 × 105 molecule / cm3 and decreased by 19%. The long-term trends of CH4 inferred from the model are in good agreement with observational results from ice core. The modeled growth rate of CO is 1 .03% / a~ 1 .06% / a in the 1980s. The model is used to investigate why CO decreased at the beginning of the 1990s. It is shown that the decrease of CO emissions is the main cause of the decrease of CO and another one is depletion of stratospheric ozone. Though decrease in CO emissions influences the de- crease of CH4 growth rate, possible decrease of CH4 emissions has little influence on the change of CO concentrations.