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Determination of atmospheric temperature



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Determination of atmospheric temperature water vapor and heating rates from mid and far infrared hyperspectral measurements AGU Fall Meeting Wednesday December 12 2007 GC34A 02 D R Feldman Caltech K N Liou UCLA Y L Yung Caltech D G Johnson LaRC M L Mlynczak LaRC Presentation Outline Motivation for studying the far infrared FIRST instrument description Sensitivity tests of mid IR vs far IR capabilities Clear sky Cloudy sky Multi instrument data comparison Climate model considerations Conclusions Outline 2 The Far Infrared Frontier Current EOS A Train measure 3 4 to 15 m don t measure 15 100 m Far IR through H2O rotational band affects OLR tropospheric cooling rates Far IR processes inferred from other spectral regions Mid IR Microwave Vis NIR Interaction between UT H2O and cirrus clouds requires knowledge of both IRIS D measured to 25 m in 1970 Currently inferred from measurements in other spectral regions Motivation No spectral measurements to the right of line Figures derived from Mlynczak et al SPIE 2002 3 FIRST Far Infrared Spectroscopy of the Troposphere FTS w 0 6 cm 1 unapodized resolution 0 8 cm scan length Multilayer beamsplitter AIRS FIRST AIRS Germanium on polypropylene Good performance over broad spectral ranges in the far infrared 5 200 m 50 2000 cm 1 spectral range NeDT goal 0 2 K 10 60 m 0 5 K 60 100 m 10 km IFOV 10 multiplexed detectors Cooling Spectrometer LN2 cooled Detectors liquid He cooled Scan time 1 4 8 5 sec Balloon borne ground based observations FIRST instrument 4 Retrieval Sensitivity Test Flow Chart T z H2O z O3 z CWC z CER z Random Perturbations Model Atmosphere RTM Noise A priori Atmospheric State A priori uncertainty RTM A priori spectrum Synthetic Measurement Retrieval algorithm Analyze retrieved state spectra and associated statistics Sensitivity tests 5 Clear Sky Retrieval Test AIRS and FIRST T z retrievals comparable FIRST better than AIRS in H2O z retrievals 200 300 mbar Residual signal in far IR seen 100 200 cm 1 low NeDT critical



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