MIPAS-STR measurements in the Arctic UTLS in winter/spring 2010: instrument characterization, retrieval and validation

摘要

The mid-infrared FTIR-limb-sounder Michelson Interferometer for PassiveAtmospheric Sounding–STRatospheric aircraft (MIPAS-STR) was deployedonboard the research aircraft M55 Geophysica during the RECONCILEcampaign (Reconciliation of Essential Process Parameters for an Enhanced Predictability of Arctic Stratospheric Ozone Lossand its Climate Interactions) in the Arctic winter/spring 2010. From the MIPAS-STR measurements,vertical profiles and 2-dimensional vertical cross-sections of temperatureand trace gases are retrieved. Detailed mesoscale structures of polar vortexair, extra vortex air and vortex filaments are identified in the results attypical vertical resolutions of 1 to 2 km and typical horizontal samplingdensities of 45 or 25 km, depending on the sampling programme. Results areshown for the RECONCILE flight 11 on 2 March 2010 and are validated withcollocated in-situ measurements of temperature, O₃, CFC-11, CFC-12 andH₂O. Exceptional agreement is found for the in-situ comparisons oftemperature and O₃, with mean differences (vertical profile/alongflight track) of 0.2/?0.2 K for temperature and ?0.01/0.05 ppmv for O₃and corresponding sample standard deviations of the mean differences of0.7/0.6 K and 0.1/0.3 ppmv. The comparison of the retrieved verticalcross-sections of HNO₃ from MIPAS-STR and the infrared limb-sounderCryogenic Infrared Spectrometers and Telescopes for the Atmosphere–NewFrontiers (CRISTA–NF) indicates a high degree of agreement. We discussMIPAS-STR in its current configuration, the spectral and radiometriccalibration of the measurements and the retrieval of atmospheric parametersfrom the spectra. The MIPAS-STR measurements are significantly affected bycontinuum-like contributions, which are attributed to background aerosol andbroad spectral signatures from interfering trace gases, and are important formid-infrared limb-sounding in the Upper Troposphere/LowerStratosphere (UTLS) region. Taking into consideration continuum-like effects, wepresent a scheme suitable for accurate retrievals of temperature and anextended set of trace gases, including the correction of a systematicline-of-sight offset.