年际时间尺度上全球植被与大气相互作用的诊断分析

Diagnosis of Global Vegetation-Atmosphere Interactions at the Interannual Time Scale

利用NOAA AVHRR得到的19年（1982-2000）全球月平均的叶面积指数（LAI）与ERA40近地面气温和CMAP降水进行时滞相关分析，并研究了LAI的年际变化对后期温度、降水的反馈作用。结果表明，大部分地区LAI与同期气温的相关性更好，30°N以北（以南）基本上为正（负）相关。LAI滞后一个月时，北半球中低纬度和20°S以南大部地区LAI与降水的正相关更强；而在北半球中纬度大陆东部和南半球热带地区，LAI与前一个月温度的关系更密切。LAI与温度的相关性在春、秋季最明显，LAI与降水的关系在雨季最密切。LAI对气温比较显著的正反馈主要分布在北半球中高纬度地区；20°S以南大部地区为比较显著的负反馈。LAI对降水比较显著的正反馈分散在北美大陆西北部、东欧平原南部、欧亚大陆东北部和热带沿海地区。中高纬度（尤其是北半球）大部分地区LAI对气温、降水反馈部分的解释方差达到总方差的20％以上。

Time-lag correlation between monthly leaf area index （LAI） derived from satellite remote sensing by NOAA Advanced Very High Resolution Radiometer （AVHRR）, 2-m air temperature from ERA40 reanalysis and precipitation from Climate Prediction Center Merged Analysis of Precipitation （CMAP） during the 19-year period （1982-2000） is analyzed for the whole year and four seasons. Self-correlations of LAI, temperature and precipitation are calculated. Feedback of LAI on later time temperature and precipitation is studied based on linear theory. By comparing the simultaneous LAI-temperature and LAI-precipitation correlations, it is found that LAI is more closely related to concurrent temperature than concurrent precipitation around most parts of the global continents, with generally positive （negative） LAI-temperature correlation coefficients to the north （south） of 30°N. As for the LAI- temperature or LAI-precipitation relationship with LAI lagging one month, LAI is more closely and positively corre- lated with antecedent precipitation in most parts of the mid-low latitudes of the Northern Hemisphere and southward of 20°S; whereas LAI is more closely connected with one-month earlier temperature in the eastern mid-latitudes of the Northern Hemisphere and in the southern tropics, with positive correlation in the mid-latitudes of the Northern Hemisphere and southern tropical Africa and negative correlation in eastern Amazon and northern Australia. The aforementioned LAI-temperature correlations are most significant during spring and autumn, whereas LAI is more closely correlated with one-month earlier precipitation during rainy seasons, i.e. JJA （June, July, August） for the Northern Hemisphere and DJF （December, January, February） for the Southern Hemisphere. Significant positive feedback of LAI on later surface temperature exists in the mid-high latitudes of North America, West Europe, and eastern Eurasian continent; whereas significant negative feedback on temperature occurs around most parts to the south of 20°S. The explained variance by the feedback of LAI on temperature can be as large as 20% of the total variance poleward of 20°S and 20°N. Significant positive feedback of LAI on precipitation occurs in northwestern Canada, southern East European plain, northeastern Eurasian continent, northern part of the Indo-China Peninsula, and coastal areas of the tropics, such as eastern Amazon plain, to the east of the East African Plateau and northwestern Australia; whereas most of the negative feedback of LAI on precipitation is not statistically significant. The explained variance by the feedback of LAI on precipitation can be as large as 20% of the total variance poleward of 20°N.