Calculation of surface and top of atmosphere radiative fluxes from physical quantities based on ISCCP data sets: 1. Method and sensitivity to input data uncertainties
Calculation of surface and top of atmosphere radiative fluxes from physical quantities based on ISCCP data sets: 1. Method and sensitivity to input data uncertainties
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DOI：
10.1029/94jd02747
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发表时间：
1995-01
影响因子：
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通讯作者：
Yuanchong Zhang;W. Rossow;A. Lacis
中科院分区：
文献类型：
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作者：
Yuanchong Zhang;W. Rossow;A. Lacis
使用一个完整的辐射传输模式和基于国际卫星云气候学项目（ISCCP）数据集的地面、大气和云的物理特性观测，计算了大气顶部和地面的上升流和下降流、短波和长波辐射通量。从1985年4月到1989年1月，每三个月在整个地球仪上每三个小时获得一次结果。进行敏感性研究是为了评估输入量的测量或规格中的估计不确定性所引起的计算通量的不确定性。除了在极地地区，云特性的不确定性不再是辐射通量不确定性的主要来源，即使在地面也是如此;相反，它们产生的不确定性与大气和地面特性造成的不确定性的大小相似。上升流短波通量的最大不确定性（10 - 15 W/m2，区域日平均值）是由陆面短波通量的不确定性引起的，而地面下降流短波通量的最大不确定性（15 - 10 W/m2，区域日平均值）与云探测误差有关。上升流长波（LW）通量（10 - 20 W/m2，区域日平均）的不确定性取决于地表温度对地表LW通量的准确性和大气温度对大气LW通量顶部的准确性。地面下沉流LW通量（10 - 15 W/m2）不确定性的主要来源是大气温度的不确定性，其次是大气湿度;除了在极地地区，云的作用很小。在陆地上，单个通量分量和总净通量的不确定性最大（15 - 20 W/m2），因为地表辐射（特别是其光谱依赖性）以及地表温度和发射率（包括其光谱依赖性）的不确定性。云是SW通量的最重要的调制器，但在陆地地区，在地面上的净SW的不确定性取决于几乎一样多的不确定性，在地面反射。虽然大气和地面温度的变化导致较大的LW通量的变化，最显着的特征是云和水汽的相对重要性随纬度的变化。由于大的自然变化，在个人通量值的不确定性主要是由采样效果，但在月平均通量的不确定性主要是由偏置误差的输入量。
Upwelling and downwelling, shortwave and longwave radiative fluxes are calculated at the top of the atmosphere and at the surface using a complete radiative transfer model and observations of the physical properties of the surface, atmosphere, and clouds based on the International Satellite Cloud Climatology Project (ISCCP) data sets. Results are obtained every three hours over the whole globe for every third month from April 1985 to January 1989. Sensitivity studies are conducted to assess the uncertainties in calculated fluxes caused by the estimated uncertainties in the measurement or specification of the input quantities. Except in the polar regions, uncertainties in cloud properties are no longer the predominant source of radiative flux uncertainty, even at the surface; rather they produce uncertainties similar in magnitude to those caused by atmospheric and surface properties. The largest uncertainty in upwelling shortwave (SW) fluxes (≈ 10–15 W/m2, regional daily mean) is caused by uncertainties in land surface albedo, whereas the largest uncertainty in downwelling SW at the surface (≈ 5–10 W/m2, regional daily mean) is related to cloud detection errors. The uncertainty of upwelling longwave (LW) fluxes (≈ 10–20 W/m2, regional daily mean) depends on the accuracy of the surface temperature for the surface LW fluxes and the atmospheric temperature for the top of atmosphere LW fluxes. The dominant source of uncertainty in downwelling LW fluxes at the surface (≈ 10–15 W/m2) is uncertainty in atmospheric temperature and, secondarily, atmospheric humidity; clouds play little role except in the polar regions. The uncertainties of the individual flux components and the total net fluxes are largest over land (15–20 W/m2) because of uncertainties in surface albedo (especially its spectral dependence) and surface temperature and emissivity (including its spectral dependence). Clouds are the most important modulator of the SW fluxes, but over land areas, uncertainties in net SW at the surface depend almost as much on uncertainties in surface albedo. Although atmospheric and surface temperature variations cause larger LW flux variations, the most notable feature of the net LW fluxes is the changing relative importance of clouds and water vapor with latitude. Uncertainty in individual flux values is dominated by sampling effects because of large natural variations, but uncertainty in monthly mean fluxes is dominated by bias errors in the input quantities.