Radiative and microphysical properties of Arctic stratus clouds from multiangle downwelling infrared radiances
Radiative and microphysical properties of Arctic stratus clouds from multiangle downwelling infrared radiances
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多角度下降红外辐射的北极层云的辐射和微物理特性
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
A. Rivers
中科院分区：
文献类型：
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作者：
C. Rathke;S. Neshyba;M. Shupe;P. Rowe;A. Rivers
[1]研究了层云多角度下行红外辐射光谱的信息量。例如，使用北冰洋表面热量平衡(SHEBA)漂流冰营的干涉仪，在距天顶成0、15、30和45�的角度测量了76组光谱。利用红外微窗口辐射角的变化，在没有辅助信息的情况下，利用几何算法确定云层温度和光学厚度。为了进行比较，光谱方法允许我们推断每个角度的云的微物理属性；因此，每个多角度集合构成了云场景水平不均匀的微物理表征。结果表明，两种方法测得的云温与激光雷达/探空仪测得的云温基本一致。多角度辐射观测也可用于计算到达地表的长波通量。我们发现，高达14Wm�2的云通量可以归因于云微物理性质的水平变化。指标术语：0320大气组成和结构：云物理和化学；0360大气组成和结构：辐射的传输和散射；3359气象学和大气动力学：辐射过程；3360气象和大气动力学：遥感；关键词：红外发射，北极云，多角度FTIR光谱，水平不均匀，长波通量，Sheba
[1] The information content of multiangle downwelling infrared radiance spectra of stratus clouds is investigated. As an example, 76 sets of spectra were measured at angles of 0, 15, 30 and 45� from zenith, using an interferometer based at the Surface Heat Budget of the Arctic Ocean (SHEBA) drifting ice camp. Exploiting the angular variation of radiance in infrared microwindows, a ‘‘geometric’’ algorithm is used to determine cloud temperature and optical depth without auxiliary information. For comparison, a spectral method allows us to infer cloud microphysical properties for each angle; each multiangle set therefore constitutes a microphysical characterization of horizontal inhomogeneity of the cloudy scene. We show that cloud temperatures determined with both approaches agree with temperatures obtained from lidar/radiosonde data. The multiangle radiance observations can also be used to calculate the longwave flux reaching the surface. We find that up to 14 W m � 2 of the overcast fluxes can be attributed to horizontal variations in cloud microphysical properties. INDEX TERMS: 0320 Atmospheric Composition and Structure: Cloud physics and chemistry; 0360 Atmospheric Composition and Structure: Transmission and scattering of radiation; 3359 Meteorology and Atmospheric Dynamics: Radiative processes; 3360 Meteorology and Atmospheric Dynamics: Remote sensing; KEYWORDS: infrared emission, Arctic clouds, multiangle FTIR Spectroscopy, horizontal inhomogeneity, longwave flux, SHEBA