Approach to the Cross-Validation of MIPAS and CHAMP Temperature and Water Vapour Profiles

Abstract

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a space-borne limb viewing mid-infrared high-resolution spectrometer launched on ENVISAT into polar orbit on 1 March 2002. Water vapour and ternperature profiles are retrievable from spectral data in an altitude range from approximately 5 km up to the mesosphere. Complementing the operational analysis of ESA, a non-operational MIPAS level 2 processor has been developed at IMK to derive geophysical data from the MIPAS observations. The IMK MIPAS level 2 data processing scheme supports a multitude of regularization approaches. Full retrieval diagnostics in terms of retrieval covariance matrices, averaging kernel matrices etc. are available. Vertical profiles of temperature and humidity have been identified to be candidate quantities for comparison with corresponding CHAMP data as part of commissioning phase as well as long-term cross-validation activities. The accuracy of MIPAS water vapour and temperature measurements is investigated by test retrievals based on simulated data. The approach to cross-validate vertical profiles of temperature and humidity from CHAMP and MIPAS, respectively, is based on the X2 of the difference of MIPAS and CHAMP retrieved profiles under consideration of error correlations, averaging kernels, and spatial and temporal mis-matching of the observations.