Global atmospheric downward longwave radiation over land surface under all‐sky conditions from 1973 to 2008
Global atmospheric downward longwave radiation over land surface under all‐sky conditions from 1973 to 2008
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DOI：
10.1029/2009jd011800
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发表时间：
2009-10
影响因子：
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通讯作者：
Kaicun Wang;S. Liang
中科院分区：
文献类型：
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作者：
Kaicun Wang;S. Liang
[1]在这篇文章中，我们首先评估了两种被广泛接受的方法来估计全球大气向下长波辐射（Ld）在晴朗和多云的条件下，使用气象观测1996年至2007年在全球分布的36个站点，由地面辐射收支网络（SURFRAD），AmeriFlux和AsiaFlux项目。地点细分为北美（20个研究中心）、亚洲（12个研究中心）、澳大利亚（2个研究中心）、非洲（1个研究中心）和欧洲（1个研究中心）。这些地点的纬度范围从赤道的0°到±50°;海拔范围从98到4700米，代表了六种不同的土地覆盖类型（沙漠、半荒漠、农田、草原、森林和湿地）。评价结果表明，全天条件下的瞬时Ld的平均偏差为2 W m−2（0.6%），平均标准偏差（SD）为20 W m−2（6%），平均相关系数（R）为0.86。全天条件下的日Ld估计为SD为12 W m−2（3.7%），平均R为0.93。这些结果表明，这两种方法可以应用于地球的大多数陆地表面。因此，我们将它们应用于全球可用的气象观测，以估计Ld的年代际变化。利用1973 - 2008年全球3200个测站的资料，分析了全球Ld在晴、多云天气下的年代际变化。我们发现，从1973年到2008年，每日Ld以每十年2.2 W m-2的平均速度增加。上升的趋势是由于空气温度、大气水蒸气和CO2浓度的增加。
[1] In this article, we first evaluate two widely accepted methods to estimate global atmospheric downward longwave radiation (Ld) under both clear and cloudy conditions, using meteorological observations from 1996 to 2007 at 36 globally distributed sites, operated by the Surface Radiation Budget Network (SURFRAD), AmeriFlux, and AsiaFlux Projects. The breakdown of locations is North America (20 sites), Asia (12 sites), Australia (2 sites), Africa (1 site), and Europe (1 site). Latitudes for these sites range from 0° at the equator to ±50°; elevation ranges from 98 to 4700 m, and six different land cover types are represented (deserts, semideserts, croplands, grasslands, forests, and wetlands). The evaluation shows that the instantaneous Ld under all-sky conditions is estimated with an average bias of 2 W m−2 (0.6%), an average standard deviation (SD) of 20 W m−2 (6%), and an average correlation coefficient (R) of 0.86. Daily Ld under all-sky conditions is estimated with a SD of 12 W m−2 (3.7%) and an average R of 0.93. These results suggest that these two methods could be applied to most of the Earth's land surfaces. Accordingly, we applied them to globally available meteorological observations to estimate decadal variation in Ld. The decadal variations in global Ld under both clear and cloudy conditions at about 3200 stations from 1973 to 2008 are presented. We found that daily Ld increased at an average rate of 2.2 W m−2 per decade from 1973 to 2008. The rising trend results from increases in air temperature, atmospheric water vapor, and CO2 concentration.