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FY-3D/HIRAS光谱定标精度评估中的最佳光谱区域选择*
周方1, 漆成莉2, 陆其峰2, 徐寒列2
(1.中国气象科学研究院;2.中国气象局国家卫星气象中心)
Optimal spectral region selection for FY-3D/HIRAS spectral calibration accuracy evaluation
Zhou Fang1, Qi Cheng Li2, Lu Qi Feng2, Xu Han Lie2
(1.Chinese Academy of Meteorological Sciences;2.National Satellite Meteorological Center,China Meteorological Administration)
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投稿时间:2019-04-01    修订日期:2020-03-09
中文摘要: 光谱定标精度的精确评估和监测,是红外高光谱数据应用之前的重要工作。光谱定标精度评估常用 “互相关”方法,即通过平移观测谱使得观测谱与参考基准谱之间满足最大相关或最小标准差条件。该方法基于极高光谱采样分辨率的参考光谱,计算资源耗用非常大,通常只选择一小段光谱区域用于评估光谱定标精度。为全面评估“互相关法”对光谱区域选择的依赖程度,基于理论模拟光谱(只考虑仪器离轴效应)对光谱区域进行初选;再基于实际观测光谱进行敏感性分析,获得最佳参考光谱区域。本文基于模拟光谱结果表明:光谱精度评估方法对光谱区域的选择在中波波段不敏感,在长波和短波波段比较敏感,其敏感性与光谱区域内吸收带的包络特征、辐射能量的大小有关;选择不同光谱区域引入的绝对误差在长波和短波波段最大分别可达3.05和3.35ppm;因此,当光谱区域选择在辐射能量较大,大气成分含量稳定的大气分子吸收带,能有效减小“互相关法”引入的误差。进一步基于风云三号D星红外高光谱大气探测仪(FY3D/HIRAS)观测光谱,研究提出了HIRAS光谱精度评估的最佳参考光谱区域:长波波段为[716, 766] cm-1,中波波段为[1270, 1320] cm-1,短波波段为[2159, 2209] cm-1,基于最佳光谱区域评估的HIRAS光谱偏差均值在三个波段均优于2ppm,偏差标准差在长波和中波优于2ppm,短波约为4ppm。本研究得到的最佳光谱区域对其他红外干涉仪器的光谱定标精度评估和频率长期稳定性监测也具有参考作用。
Abstract:Accurately evaluation and monitoring of spectral frequency accuracy is significant for an hyper-spectral infrared (IR) interferometer before data application. A “cross-correlation method” is commonly used to evaluate the accuracy of the spectral accuracy, which allows the maximum correlation, or minimum standard deviation condition, to be met between an observed and a simulated spectrum by shifting the observed spectrum. The cross-correlation method is based on spectrum that with high spectral sampling resolution, so for saving calculation load, narrow spectral regions are usually to be chosen. To comprehensively evaluate the dependence of the “cross-correlation method” on spectral regions, a preliminary selection of spectral regions was carried out based on the simulated spectra (with only the off-axis effect of the instrument considered) . Sensitivity study of spectral regions selection was then performed using on-orbit data and obtained the best reference spectral regions. The results that based on simulated spectra show spectral regions selection is sensitive to the evaluation method in long-wave (LW) and short-wave (SW) bands, and insensitive in mid-wave (MW) band; in addition, the sensitivity is related to the envelope characteristics and to the radiation energy of the absorption line in the spectral regions. The absolute errors for selecting different spectral regions can reach 3.05 and 3.35 ppm in LW and SW bands, respectively. Selecting high-radiation-energy and stable atmospheric composition regions can effectively reduce the error introduced by the “cross-correlation method” . Results using on-orbit data of high-spectral-resolution infrared atmospheric sounder (HIRAS), which was firstly carried on FengYun 3D (FY-3D) satellite, show that the instrument observation error and radiative transfer model simulation error are also needed to be considered in practical data applications to achieve the best spectral regions. Finally the best reference spectral regions for HIRAS spectral accuracy evaluation were obtained and locate in 716-766 cm-1 for LW band, 1270-1320 cm-1 for MW band and 2159-2209 cm-1 for SW band, respectively. The mean spectral bias results that based on the selected best reference spectra regions for HIRAS are all less than 2 ppm for the 3 bands, spectral bias standard deviations are less than 2 ppm for LW and MW bands, and about 4 ppm for SW band. The obtained best spectral regions are also applicable to the spectral frequency accuracy evaluation and long-term frequency monitoring of other infrared interference instruments.
文章编号:201904010132     中图分类号:P412.27    文献标志码:
基金项目:国家重点研发计划项目(2016FYB0500704, 2018FYB0504700,2018FYB0504703)、国家自然科学基金(41505029);“万人计划”领军人才(批号187)。
引用文本:
周方,漆成莉,陆其峰,徐寒列,0.[en_title][J].Meteor Mon,():-.
Zhou Fang,Qi Cheng Li,Lu Qi Feng,Xu Han Lie,0.Optimal spectral region selection for FY-3D/HIRAS spectral calibration accuracy evaluation[J].Meteor Mon,():-.