北半球近地层典型区CO_2体积分数时空分布及成因

利用GEOS-Chem全球三维大气化学传输模式,分析了北半球近地层CO2体积分数的时空变化特征及其成因。2006—2010年的5 a的模拟结果表明:北半球中纬度近地层CO2体积分数存在着两个高值中心,即亚洲东部和北美东北部。在季节尺度上,亚洲东部CO2体积分数最大值出现在春季,而北美东北区域CO2体积分数最大值出现在冬季;而两个地区的CO2体积分数最低值都出现在夏季。在年际尺度上,两个区域CO2体积分数的年际变率增幅明显高于北半球其它区域,且CO2体积分数高值出现时间的年际差异较大。另外,模拟分析发现北半球森林、农田、草原典型区域,所对应的CO2体积分数具有不同的季节变化特点,它们的CO2季节内变幅依次减小。进一步分析发现3种不同典型区域的CO2体积分数与叶面积指数(LAI)季节变化,具有很好的负相关性。可见陆地生态系统作为碳汇,对近地层CO2体积分数的季节变化具有重要的作用。而温度和降水是影响LAI的最重要的两个气象因子,它们与CO2体积分数季节变化存在内在联系,模拟结果表明北半球大部分陆地近地层CO2体积分数与温度、降水呈现显著的负相关。

Spatial-temporal distribution and cause of volume fraction of CO2 in northern hemisphere

Based on the GEOS-Chem model, the spatial-temporal characteristics and cause of surface CO₂ concentration are simulated and analyzed during 2006-2010. The results show that two high CO₂ concentration centers of northern hemisphere exist in East Asia and Northeast America. For East Asia, the maximum CO₂ concentration appears in spring, while for Northeast America, it happens in winter. And the minimum ones of these two regions apper both in summer. Moreover, the interannual growth of CO₂ volume fraction in these two regions is higher compared to other areas of northern hemisphere and the time, during which the maximum CO₂ concentration appears, changes yearly. In addition, the seasonal variation features of CO₂ concentration are different in forest, cropland and grassland with the decreasing of amplitude of seasonal cycle in turn. Furthermore, surface CO₂ concentration has a significant negative correlation with leaf area index(LAI), which means that the ecosystem, as an important carbon sink, affects the seasonal variation of surface CO₂ concentration. Two important factors (temperature and precipitation) influencing LAI also have a close relationship with surface CO₂ concentration. Correlation analysis indicates that surface CO₂ concentration has a significant negative correlation with temperature and precipitation in most part of land in northern hemisphere.