Monday, 15 January 2007: 5:15 PM
Method and results of retrieval of HDO/H2O in atmosphere from satellite IMG/ADEOS and ground-based FTIR data
212B (Henry B. Gonzalez Convention Center)
In this paper we present Principal Components (PCs) method for retrieval of the HDO/H2O vertical profile using atmospheric radiances observed from space by sensor like IMG as well as atmospheric transmittance spectra observed by ground based FTIR. The method is based on the expansion of the retrieved profile on eigenvectors of covariance matrix of model profiles extracted from the isotopic Atmospheric General Circulation Model (AGCM). Error estimation of the retrieval scheme is made using closed model computations with synthetic spectra of IMG and known sets of T, H2O, HDO profiles and its value is within 8‰ - 70‰ for vertical profile and not greater than 18‰ for columnar value of HDO/H2O ratio. The method was applied to IMG/ADEOS spectra measured over the ocean in clear sky conditions. Latitudinal distributions of HDO/H2O profile and columnar HDO/H2O ratio are retrieved over Pacific Ocean for the time interval from winter of 1996 to summer of 1997. The retrieved HDO/H2O from IMG/ADEOS data and simulated with isotopic AGCM are in a good agreement. FTIR is Poker Flat high resolution ground-based Fourier transform spectrometer for routine up-looking observation of atmosphere in the spectral range from 750-4300 cm-1 with resolution 0.002 cm-1 and high signal to noise ratio. The spectrometer is located at the Poker Flat Research Range (Altitude 0.61km; latitude 65.11N; longitude 147.42W) of the Geophysical Institute at the University of Alaska Fairbanks. Measured by the FTIR atmospheric transmittances are supported by zonde observations of T and water vapour profiles. The HDO/H2O PCs retrieval method was also adapted for using high spectral resolution atmospheric transmittances observed by ground-based sensors like the FTIR. Linear regression of the PCs was used in this case. Error estimation of this retrieval scheme was also made using closed model computations with synthetic spectra of the FTIR and known sets of T, H2O, HDO profiles. The errors are within 6‰ - 70‰ for vertical profile and not greater than 6‰ for columnar value of HDO/H2O ratio. As an example, HDO/H2O vertical profiles were retrieved using a few samples of FTIR spectra observed at the Poker Flat Research Range from 2000 to 2004 and compared with isotope AGCMs outputs for Alaska's atmosphere.