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气象:2020,46(6):733-744
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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,漆成莉,陆其峰,徐寒列
(中国气象科学研究院,北京 100081;国家卫星气象中心,北京 100081;中国气象局中国遥感卫星辐射测量和定标重点开放实验室,北京 100081;中国气象科学研究院灾害天气国家重点实验室,北京 100081)
Optimal Spectral Region Selection for FY-3D/HIRAS Spectral Calibration Accuracy Evaluation
ZHOU Fang,QI Chengli,LU Qifeng,XU Hanlie
(Chinese Academy of Meteorological Sciences, Beijing 100081; National Satellite Meteorological Centre, Beijing 100081; Key Laboratory of Radiometric Calibration and Validation for Environmental Satellites, CMA, Beijing 100081; State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081)
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投稿时间:2019-04-10    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。考虑到计算耗时,无须在全谱段检测频偏,而用部分光谱区域评估光谱定标精度。为全面评估“互相关法”对光谱区域选择的依赖程度,初步选择光谱区域依据理论模拟光谱(只考虑仪器离轴效应)的敏感性分析,最佳光谱区域选择基于实际观测光谱的敏感性分析。基于模拟光谱的敏感性分析表明: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3.35 ppm(1 ppm=10-6);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(FY-3D/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[1 〖KG-*5〗270,1 〖KG-*5〗320] cm-1,短波波段为[2 〖KG-*5〗159,2 〖KG-*5〗209] cm-1,基于上述光谱区域评估的HIRAS光谱偏差平均值均优于2 ppm,长波和中波的标准差优于2 ppm,短波的标准差约为4 ppm。研究结果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:Accurate 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. From the perspective of the time-consuming calculation, it is not necessary to detect the frequency offset in the entire spectrum, but to evaluate the accuracy of the spectral calibration with a part of the spectral region. 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 sensitivity analysis of the simulated spectra (with only the off-axis effect of the instrument considered), and the optimal spectral region was selected based on the sensitivity analysis of the on-orbit data. The results based on simulated spectra showed that spectral region selection is sensitive to the evaluation method in long-wave (LW) and short-wave (SW) bands, but insensitive in mid-wave (MW) band. In addition, the sensitivity is rela-ted 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 (1 ppm=10-6) 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” . The results using on-orbit data of high-spectral-resolution infrared atmospheric sounder (HIRAS), which was firstly carried on the Fengyun 3D (FY-3D) satellite, showed 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, located in 716-766 cm-1 for LW band, 1 〖KG-*5〗270-1 〖KG-*5〗320 cm-1 for MW band and 2 〖KG-*5〗159-2 〖KG-*5〗209 cm-1 for SW band, respectively. The mean spectral bias results based on the selected best reference spectra regions for HIRAS are all less than 2 ppm for the three 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.
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基金项目:国家重点研发计划(2016FYB0500704、2018FYB0504700、2018FYB0504703)、国家自然科学基金项目(41505029)和“万人计划”领军人才(批号187)共同资助
引用文本:
周方,漆成莉,陆其峰,徐寒列,2020.FY-3D/HIRAS光谱定标精度评估中的最佳光谱区域选择[J].气象,46(6):733-744.
ZHOU Fang,QI Chengli,LU Qifeng,XU Hanlie,2020.Optimal Spectral Region Selection for FY-3D/HIRAS Spectral Calibration Accuracy Evaluation[J].Meteor Mon,46(6):733-744.