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
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摘要
快速辐射传输模式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.针对FY-4 AGRI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)光学厚度预报因子的快速正演算子,与逐线积分模式的结果对比,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.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于0.6K.v9模式在水汽和温度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模式预报因子中,引入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.
The fast radiative transmission model can quickly calculate the transmittances coefficients by extending a series of optical depth core functions and channel spectral characteristics,so as to obtain an accuracy that is compatible with the line-by-line model. In this paper,four fast forward operators are established to predict the optical depth( OD) of mixed gas,water vapor line absorption and water vapor continuum absorption of RTTOV v7,v8,v9 and CRTM v2. 1 in 6 infrared channels of AGRI in FY-4. The largest STDs of all the four fast operators are less than 0. 6 K in brightness temperature of AGRI. The STD of water vapor,CO_2 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. Experiments were also conducted using standard atmospheric profiles to calculate the Jacobine and OD of the mixed gas,water vapor absorption and water vapor continuum absorption. 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.
The fast radiative transmission model can quickly calculate the transmittances coefficients by extending a series of optical depth core functions and channel spectral characteristics,so as to obtain an accuracy that is compatible with the line-by-line model. In this paper,four fast forward operators are established to predict the optical depth( OD) of mixed gas,water vapor line absorption and water vapor continuum absorption of RTTOV v7,v8,v9 and CRTM v2. 1 in 6 infrared channels of AGRI in FY-4. The largest STDs of all the four fast operators are less than 0. 6 K in brightness temperature of AGRI. The STD of water vapor,CO_2 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. Experiments were also conducted using standard atmospheric profiles to calculate the Jacobine and OD of the mixed gas,water vapor absorption and water vapor continuum absorption. 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.
引文
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[15]Qi C.A Sampling Technique of Typical Atmospheric Profiles Database in China[J].Journal of Applied Meteorological Science,(漆成莉,刘辉,马刚,等.中国区域典型大气廓线样本库的一种选择方法,应用气象学报),2010,21(1):70-75.
[16]Edwards D P.GENLN2:A general line-by-line atmospheric transmittance and radiance model.Version 3.0:Description and users guide[C].NCAR Technical Note,NCAR/TN-367+STR,Boulder,CO.1992.
[2]Mcmillin L M,Fleming H E.Atmospheric transmittance of an absorbing gas:a computationally fast and accurate transmittance model for absorbing gases with constant mixing ratios in inhomogeneous atmospheres.[J].Applied optics,1976,15(2):358.
[3]Mcmillin L M,Crone L J,Kleespies T J.Atmospheric transmittance of an absorbing gas.5.Improvements to the OPTRAN approach.[J].Applied Optics,1995,34(36):8396.
[4]Eyre J R,Woolf H M.Transmittance of atmospheric gases in the microwave region:a fast model.[J].Applied Optics,1988,27(15):3244-9.
[5]Eyre J R.A fast radiative transfer model for satellite sounding systems[C]//ECMWF Research Dept.Tech.Memo176,ECMWF.1991.
[6]Matricardi M,Chevallier F,Kelly G,et al.An improved general fast radiative transfer model for the assimilation of radiance observations[J].Quarterly Journal of the Royal Meteorological Society,2004,130(596):153-173.
[7]Saunders R,Matricardi M,Brunel P.An improved fast radiative transfer model for assimilation of satellite radiance observations[J].Quarterly Journal of the Royal Meteorological Society,2015,125(556):1407-1425.
[8]MA Gang,QIU Chong-Jian,LI Guang-Qing,et al.Study of simulation on radiance from infrared and water vapor channel of fy2b by a fast forward model-rttov7[J].J.Infrared Millim.Waves.(马刚,邱崇践,黎光清,等.利用RTTOV7快速辐射传输模式模拟风云二号红外和水汽成像通道辐射率的研究.红外与毫米波学报),2006,25(1):37-40.
[9]Chen Y,Han Y,Liu Q,et al.Community Radiative Transfer Model for Stratospheric Sounding Unit[J].Journal of Atmospheric&Oceanic Technology,2011,28(28):767-778.
[10]Chen Y,Han Y,Weng F.Comparison of two transmittance algorithms in the community radiative transfer model:Application to AVHRR[J].Journal of Geophysical Research Atmospheres,2012,117(D6):561-8.
[11]Kratz D P,Mlynczak M G,Mertens C J,et al.An intercomparison of far-infrared line-by-line radiative transfer models[J].Journal of Quantitative Spectroscopy&Radiative Transfer,2005,90(3-4):323-341.
[12]R9REP2008 RTTOV-9 science and validation report available at:http://research.metoffice.gov.uk/research/interproj/nwpsaf/rtm/rttov9_files/rttov9_svr.pdf Saunders
[13]Han Y,Delst P V,Liu Q,et al.User's Guide to the JCSDACommunity Radiative Transfer Model(Beta Version)[J].NIST TN-1442,2005.
[14]Li Xiaokun,Wang Ganjin,Chen Guilin,FY-4 imager:visible channel star sensing[J].Science Technology and Engineering,(李晓坤、王淦全、陈桂林.风云四号气象卫星扫描成像仪-可见光通道星敏感.科学技术与工程),2007,7(6):993-996.
[15]Qi C.A Sampling Technique of Typical Atmospheric Profiles Database in China[J].Journal of Applied Meteorological Science,(漆成莉,刘辉,马刚,等.中国区域典型大气廓线样本库的一种选择方法,应用气象学报),2010,21(1):70-75.
[16]Edwards D P.GENLN2:A general line-by-line atmospheric transmittance and radiance model.Version 3.0:Description and users guide[C].NCAR Technical Note,NCAR/TN-367+STR,Boulder,CO.1992.