Advanced retrievals of multilayered cloud properties using multispectral measurements
Advanced retrievals of multilayered cloud properties using multispectral measurements
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DOI：
10.1029/2004jd005101
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发表时间：
2005-08
影响因子：
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通讯作者：
Jianping Huang;P. Minnis;B. Lin;Y. Yi;M. Khaiyer;R. Arduini;Alice Fan;G. Mace
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文献类型：
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作者：
Jianping Huang;P. Minnis;B. Lin;Y. Yi;M. Khaiyer;R. Arduini;Alice Fan;G. Mace
收稿日期：2004年6月6日;修订日期：2004年9月2日;接受日期：2004年10月4日;发表日期：2005年4月13日。[1]目前的卫星云反演通常是基于这样的假设，即所有的云由一个均匀的单层，尽管云重叠频繁发生。因此，云重叠将导致许多云属性的检索中出现较大的错误。为了解决这一问题，一个多层云反演系统（MCRS）的发展相结合的卫星可见光和红外辐射和地面微波辐射计测量。利用一个双层云模式模拟了水上冰云的辐射特性。利用微波液态水并假设有效水滴尺寸，估算了低云和地面的辐射。这些辐射取代传统上用于单层云检索的背景辐射。MCRS适用于2000年3月至10月的数据超过四个大气辐射测量（ARM）南部大平原（SGP）网站。结果进行了比较，从雷达数据的冰水路径（IWP）的可用检索，并表明MCRS清楚地产生更准确的检索冰在水云的属性。MCRS得到的IWP值与雷达反演的IWP值最接近。对于水上冰云系统，平均而言，光学厚度和IWP从最初的高估值减少了约30%。MCRS反演的3 ~ 10月平均云有效温度降低了10 ± 12 K，平均高度差减小了1.4km，表明传统的单层反演方法低估了冰云高度，中层冰云覆盖率偏高。有效的冰晶颗粒尺寸仅增加了几个百分点的新方法。这种新的基于物理的技术应当是可靠的，并且在卫星成像器和适当的卫星或地面微波传感器同时提供数据时可以直接应用。
Received 6 June 2004; revised 2 September 2004; accepted 4 October 2004; published 13 April 2005. [1] Current satellite cloud retrievals are usually based on the assumption that all clouds consist of a homogenous single layer despite the frequent occurrence of cloud overlap. As such, cloud overlap will cause large errors in the retrievals of many cloud properties. To address this problem, a multilayered cloud retrieval system (MCRS) is developed by combining satellite visible and infrared radiances and surface microwave radiometer measurements. A two-layer cloud model was used to simulate ice-over-water cloud radiative characteristics. The radiances emanating from the combined low cloud and surface are estimated using the microwave liquid water with an assumption of effective droplet size. These radiances replace the background radiances traditionally used in single-layer cloud retrievals. The MCRS is applied to data from March through October 2000 over four Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) sites. The results are compared to the available retrievals of ice water path (IWP) from radar data and show that the MCRS clearly produces a more accurate retrieval of ice-over-water cloud properties. MCRS yields values of IWP that are closest to those from the radar retrieval. For ice-over-water cloud systems, on average, the optical depth and IWP are reduced, from original overestimates, by approximately 30%. The March–October mean cloud effective temperatures from the MCRS are decreased by 10 ± 12K,whichtranslatestoanaverageheightdifferenceof � 1.4km.Theseresultsindicatethat ice-cloud height derived from traditional single-layer retrieval is underestimated, and the midlevel ice cloud coverage is over classified. Effective ice crystal particle sizes are increased by only a few percent with the new method. This new physically based technique should be robust and directly applicable when data are available simultaneously from a satellite imager and the appropriate satellite or surface microwave sensor.