Upper tropospheric humidity and cirrus geometrical and optical thickness: Relationships inferred from 1 year of collocated AIRS and CALIPSO data
Upper tropospheric humidity and cirrus geometrical and optical thickness: Relationships inferred from 1 year of collocated AIRS and CALIPSO data
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对流层上层湿度与卷云几何和光学厚度：根据 1 年同期的 AIRS 和 CALIPSO 数据推断出的关系
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
J. Pelon
中科院分区：
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作者：
N. Lamquin;C. Stubenrauch;J. Pelon
由星载被动遥感确定的相对于冰的相对湿度剖面(RHice)缺乏垂直和空间分辨率。与现场观测相比，RHice分布显示出干燥的偏差，因为几何上较薄的潮湿层被整合在较粗的垂直分辨率内，其直接影响是低估了冰过饱和(RHice&>100%)的发生。来自大气红外探测仪(AIRS)和云气溶胶激光雷达和红外探路者卫星观测(CALIPSO)的配置数据提供了调查对流层顶附近高云的几何厚度和光学厚度之间的关系的机会。从CALIPSO得到了单层高云的“视”光学厚度。通过将这些“视”光学厚度与大气的云红外发射率进行比较，可以估计多次散射的贡献，并对光学厚度进行修正。平均RHice随着云层几何厚度的增加而增加，但与100%相比保持较低，但非常垂直延伸的云层除外。平均而言，光学厚度较厚的云比光学厚度较薄的云显示出更大的几何厚度和更大的相对湿度。然而，在几何厚度相当的情况下，光学较薄的云层平均会稍微潮湿一些。研究表明，云的几何厚度比云的光学厚度对粗垂直分辨率下的RHICE的影响更大。讨论了空气湿度观测在探测冰过饱和度方面的局限性。
Profiles of relative humidity with respect to ice (RHice) determined from spaceborne passive remote sensing suffer a lack of vertical and spatial resolutions. RHice distributions show dry biases compared to in situ observations because geometrically thin moist layers are integrated within coarser vertical resolutions, a direct effect being the underestimation of ice supersaturation (RHice > 100%) occurrence. Collocated data from the Atmospheric Infrared Sounder (AIRS) and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) provide the opportunity to investigate relationships between RHice and geometrical thickness and optical depth of high clouds near the tropopause. “Apparent” optical depths are derived for single-layer high clouds from CALIPSO. By comparing these “apparent” optical depths to cloud infrared emissivities derived from AIRS the multiple scattering contribution is estimated and the optical depths are corrected. Mean RHice increases with cloud geometrical thickness but remains low compared to 100% except for very vertically extended clouds. Optically thicker clouds show on average larger geometrical thickness and larger relative humidity than optically thinner clouds. However, for a comparable geometrical thickness, optically thinner clouds are on average slightly more humid. This study concludes that cloud geometrical thickness has a greater influence than cloud optical depth on RHice integrated within a coarse vertical resolution. Limitations of AIRS humidity observations regarding the detection of ice supersaturation are discussed.