Abstract
Abstract. The mid-infrared FTIR-limb-sounder Michelson Interferometer for Passive Atmospheric Sounding–STRatospheric aircraft (MIPAS-STR) was deployed onboard the research aircraft M55 Geophysica during the RECONCILE campaign (Reconciliation of Essential Process Parameters for an Enhanced Predictability of Arctic Stratospheric Ozone Loss and its Climate Interactions) in the Arctic winter/spring 2010. From the MIPAS-STR measurements, vertical profiles and 2-dimensional vertical cross-sections of temperature and trace gases are retrieved. Detailed mesoscale structures of polar vortex air, extra vortex air and vortex filaments are identified in the results at typical vertical resolutions of 1 to 2 km and typical horizontal sampling densities of 45 or 25 km, depending on the sampling programme. Results are shown for the RECONCILE flight 11 on 2 March 2010 and are validated with collocated in-situ measurements of temperature, O3, CFC-11, CFC-12 and H2O. Exceptional agreement is found for the in-situ comparisons of temperature and O3, with mean differences (vertical profile/along flight track) of 0.2/−0.2 K for temperature and −0.01/0.05 ppmv for O3 and corresponding sample standard deviations of the mean differences of 0.7/0.6 K and 0.1/0.3 ppmv. The comparison of the retrieved vertical cross-sections of HNO3 from MIPAS-STR and the infrared limb-sounder Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere–New Frontiers (CRISTA–NF) indicates a high degree of agreement. We discuss MIPAS-STR in its current configuration, the spectral and radiometric calibration of the measurements and the retrieval of atmospheric parameters from the spectra. The MIPAS-STR measurements are significantly affected by continuum-like contributions, which are attributed to background aerosol and broad spectral signatures from interfering trace gases, and are important for mid-infrared limb-sounding in the Upper Troposphere/Lower Stratosphere (UTLS) region. Taking into consideration continuum-like effects, we present a scheme suitable for accurate retrievals of temperature and an extended set of trace gases, including the correction of a systematic line-of-sight offset.
Highlights
Airborne and balloon-borne remote-sensing measurements are filling the gap between in-situ measurements and satellite-borne remote-sensing measurements in terms of spatial coverage and spatial resolution
Several in-situ instruments were deployed onboard the Geophysica during the RECONCILE campaign, allowing for comparisons with the MIPAS-STR results (Table 3)
CFC-11 and CFC-12 measurements were provided by the High Altitude Gas AnalyzeR (HAGAR)
Summary
Airborne and balloon-borne remote-sensing measurements are filling the gap between in-situ measurements and satellite-borne remote-sensing measurements in terms of spatial coverage and spatial resolution. Including the uncertainties inherent to the AHRS, the accuracy of the scan-mirror adjustment and the uncertainties resulting from the LOS retrieval, a total pointing accuracy of 0.78 arcmin (1σ ) is estimated This value corresponds to about 3 % of the instrumental FOV or about 100 m at the lowest tangent altitude. The atmospheric measurements with negative elevation angles, which are characterized by their tangent altitudes, allow for the retrieval of vertically resolved profiles of atmospheric temperature and trace gases below flight altitude. Tangent altitudes below 9 km are omitted and upwardscanning is performed less frequently, resulting in a total time of about 2.4 min for one full limb scan, corresponding to a horizontal sampling along flight track of approximately 25 km. The latter three steps are carried out separately for each interferometer scan direction (forward/backward sweeps are carried out alternatingly), since the data-acquisition is slightly different
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