Impact of surface inhomogeneity on solar radiative transfer under overcast conditions
Impact of surface inhomogeneity on solar radiative transfer under overcast conditions
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DOI：
10.1029/2001jd000976
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发表时间：
2002-08
影响因子：
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通讯作者：
Zhanqing Li;M. Cribb;A. Trishchenko
中科院分区：
文献类型：
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作者：
Zhanqing Li;M. Cribb;A. Trishchenko
[1]本研究的目的是评估的能力，中等分辨率透射率4（MODTRAN-4）代码模拟高分辨率短波（SW）通量详细和完整的输入信息在阴天条件下。研究强调了地表不均匀性对西南辐射传输闭合的影响。它还导致了一种方法，估计表面光谱面积平均辐射从下降流太阳透射率测量。调查利用了一套仪器收集的大量大气辐射测量（ARM）现场数据，包括宽带和窄带辐射计和光谱仪，云雷达和激光雷达，微波辐射计，大气探测仪器和卫星数据。为MODTRAN-4程序提供观测到的大气、云和地表参数，生成地表的太阳光谱透射率和大气顶部的反射率（TOA）。的透射率进行了比较，与旋转阴影波段光谱辐射计的测量，并显示在近红外（NIR）区域，其中大部分是由于使用不具代表性的表面光谱反射率显着的差异。开展了一项实地活动，收集ARM中央设施附近各种土地覆盖类型的地表覆盖数据。将采样数据与基于专题成像仪/陆地卫星的土地覆盖分类数据相结合，绘制地表光谱图。代入MODTRAN-4模型的推导出的面积平均光谱反射率消除了近红外光谱的主要差异，也导致了良好的协议与地面太阳宽带通量和TOA卫星光谱反射率。在这些发现的基础上，人们可以使用下降流光谱透射率数据，连同详细的云和大气信息，以估计表面有效面积平均反射率。估算值与地面调查数据吻合较好。根据该方法，获得了全年有效面积平均光谱通量数据集。
[1] The goal of this study was to assess the ability of the Moderate-Resolution Transmittance 4 (MODTRAN-4) code to simulate high-resolution shortwave (SW) fluxes given detailed and complete input information under overcast conditions. The study underlines the impact of surface inhomogeneity on the closure of SW radiative transfer. It also leads to a method of estimating surface spectral areal-mean albedo from downwelling solar transmittance measurements. The investigation made use of ample Atmospheric Radiation Measurement (ARM) field data collected by a suite of instruments, including broadband and narrowband radiometers and spectrometers, cloud radar and lidar, microwave radiometer, atmospheric sounding instruments, and satellite data. Furnishing the MODTRAN-4 code with observed atmospheric, cloud, and surface parameters generates spectral solar transmittance at the surface and reflectance at the top of the atmosphere (TOA). The transmittances were compared with the Rotating Shadowband Spectroradiometer measurements and showed significant discrepancies in the near-infrared (NIR) region, the bulk of which was attributed to the use of unrepresentative surface spectral albedos. A field campaign was undertaken to collect surface albedo data for a wide variety of land cover types near the ARM Central Facility. The sampled data were combined with thematic mapper/Landsat-based land cover classification data to map surface spectral albedo. Substitution of the derived areal-mean spectral albedo into the MODTRAN-4 model eliminates major discrepancies in the NIR, and also leads to good agreements with surface solar broadband fluxes and TOA satellite spectral reflectance. On the basis of these findings, one may use downwelling spectral transmittance data, together with detailed cloud and atmospheric information, to estimate surface effective areal-mean albedo. The estimated values agree well with those derived from the ground survey data. Following the method, a data set of effective areal-mean spectral albedo throughout a year was obtained.