A Sequential Estimation Approach to Cloud‐Clearing For Satellite Temperature Sounding
A Sequential Estimation Approach to Cloud‐Clearing For Satellite Temperature Sounding
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DOI：
10.1002/qj.49711347814
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发表时间：
1987-10
影响因子：
8.9
通讯作者：
J. Eyre;P. Watts
中科院分区：
文献类型：
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作者：
J. Eyre;P. Watts
利用星载红外辐射计探测对流层温度，由于云层对所测辐射量的影响而变得复杂。如果要获得准确的产品，必须首先检测这些影响，如果可能，必须在检索程序中对其进行校正。这通常是通过将测量到的辐射值转换为在无云情况下从同一大气剖面观测到的“晴空柱”值来完成的，这一过程称为“放云”。本文对近年来国内外清除云层的方法进行了综述。在此基础上，提出了一种基于最优估计原理的新方法，并将其应用于TIROS-N/NOAA卫星系列的高分辨率红外辐射测深仪（HIRS）数据。根据云的特征，通过几种方法中的一种，在每个高红外点获得了清晰柱辐射及其预期误差的初步估计。然后利用透明柱辐射场中预期的水平一致性特性来改进使用顺序估计程序的初始估计。本计划拟在天文台的局部区域探测系统中实施，该系统提供高水平分辨率的卫星探测，以供实际天气预报使用。文中给出了新方案及其所取代的旧方案的详细情况。通过将新旧方案的产品与AVHRR（先进甚高分辨率辐射计）同步数据的清柱辐射度进行比较，证明了清柱辐射度的改善。
Temperature sounding of the troposphere using satellite-borne infrared radiometers is complicated by the effects of clouds on the measured radiances. If accurate products are to be obtained these effects must first be detected and, if possible, corrections must be made for them in the retrieval procedures. This is normally done by converting the measured radiances to the ‘clear-column’ values which would be observed from the same atmospheric profile in the absence of cloud—a process known as ‘cloud-clearing’. In this paper a review of cloud-clearing methods is presented. Then a new approach to cloud-clearing, based on the principles of optimal estimation, is developed and applied to data from HIRS (the High-resolution Infrared Radiation Sounder) on the TIROS-N/NOAA satellite series. Preliminary estimates of clear-column radiances and their expected errors are obtained at each HIRS spot by one of a number of methods, depending on the cloud characteristics. the properties of horizontal consistency expected in the clear-column radiance field are then employed to improve the initial estimates using a sequential estimation procedure. This scheme is intended for implementation in the Local Area Sounding System of the Meteorological Office, which provides satellite soundings of high horizontal resolution for use in operational weather forecasting. Details of the new scheme, and of the old scheme which it replaces, are given. the improvements in clear-column radiances are demonstrated by comparing the products of the old and new schemes with clear-column radiances derived from coincident data of AVHRR (the Advanced Very High Resolution Radiometer).