光学厚度预报因子对风云四号卫星扫描辐射计红外通道快速正演精度的影响分析
投稿时间:2017-06-09  修订日期:2018-01-18  点此下载全文
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作者单位E-mail
马刚 国家卫星气象中心 magang@cma.cn 
基金项目:公益性行业(气象)科研专项(GYHY201506022,GYHY201506002)
中文摘要:快速辐射传输模式在等压层对光学厚度的核函数作级数展开,利用光学厚度预报因子与卫星通道光谱特征系数可实现通道透过率的快速计算,并达到与逐线积分模式相当的正演精度。本文针对FY4AGRI(Advanced Geostationary Radiation Imager)的6个红外通道,分别建立了基于RTTOVv7、v8、v9和CRTMv2.1(以下简称四种模式)的光学厚度预报因子的快速正演算子,与GENLN2 逐线积分模式的计算结果进行对比,分析了四种快速正演算子中均匀混合气体、水汽线吸收和水汽连续吸收预报因子对正演误差的影响。利用NESDIS 34大气廓线样本库的分析表明,四种快速正演模式计算通道亮温与逐线模式结果相比,在温度探测通道的最大标准差要小0.6K。RTTOVv9在水汽和CO2探测通道的正演误差远小于其他三个模式;四个模式在窗区通道的误差基本相当。V9模式正演通道透过率的误差最小,并且在大气中低层的误差小于大气中高层;v2.1的正演误差在水汽和CO2探测通道最大。利用标准大气廓线对四个模式正演Jacobine和3种光学厚度的分析表明,v9利用实时大气与参考大气的整层离差减小了均匀混合气体光学厚度的正演误差。总体而言,对星载滤光片式红外成像/探测仪的快速正演,在已知快速正演模式中,RTTOV v9对温度和水汽探测通道的误差最小,而在窗区通道与其它三个模式的误差水平相当。
中文关键词:光学厚度预报因子  风云四号  红外成像通道  快速正演  精度影响
 
Impact to precision of fast simulated brightness temperature toinfrared channels of FY4 AGRI from optical depth predictors
Abstract:The radiative transfer models arevital is important in atmospheric quantitative remote sensing. They can quickly calculate the transmittances coefficients through expanding series of core function of optical depth and property of channel’s spectral to get compatible accuracy to that of the line-by-line models. In this paper, four fast forward models have been set up to predict optical depth (OD)of mixed gas, water vapor line absorption and water vaporcontinuum absorption of RTTOV v7, v8, v9 and CRTM v2.1 in 6 infrared channels of AGRI in FY4. Based on the NESDIS 34 database,the OD STDs of all the four fast models are less than 0.6K in brightness temperatureof AGRI while they are larger than 0.6k in GENLN2. The OD errors of water vapor, CO2 and channel transmittances simulation in RTTOV v9 are the smallest among the four models. And the errors are less in lower levels than that of higher levels in the channel transmittances simulation. And the errors are the largest in water vapor and CO2 profiles simulation in CRTM v2.1. Experiments have also been done with standard atmospheric profiles to calculate the Jacobine and OD of mixed gas, water vapor line absorption and water vapor continuum absorption with the four operators. The OD errors of the mixed gas decrease with the new information of the deviations of real atmosphere profiles and the reference ones in v9. Simulations of OD of water vapor are improved by 19 water vapor line absorption profiles and 4 water vapor continuum absorption ones in v9. All the results also indicate that the fast radiative models RTTOV v9 can perform the best in the temperature and water vapor sounding channels among the four models, even compared with GENLN2.
keywords:Optical depth predictor, Fengyun4 satellite, Infrared imager channels fast radiative transfer simulation, impact to precision
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