Geophysical validation of MIPAS-ENVISAT operational ozone data

[摘要] The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS),on-board the European ENVIronmental SATellite (ENVISAT) launched on1 March 2002, is a middle infrared Fourier Transform spectrometer measuring theatmospheric emission spectrum in limb sounding geometry. The instrument iscapable to retrieve the vertical distribution of temperature and trace gases,aiming at the study of climate and atmospheric chemistry and dynamics, and atapplications to data assimilation and weather forecasting. MIPAS operated inits standard observation mode for approximately two years, from July 2002 toMarch 2004, with scans performed at nominal spectral resolution of 0.025 cm⁻¹and covering the altitude range from the mesosphere to the uppertroposphere with relatively high vertical resolution (about 3 km in thestratosphere). Only reduced spectral resolution measurements have beenperformed subsequently. MIPAS data were re-processed by ESA using updatedversions of the Instrument Processing Facility (IPF v4.61 and v4.62) andprovided a complete set of level-2 operational products (geo-located verticalprofiles of temperature and volume mixing ratio of H₂O, O₃,HNO₃, CH₄, N₂O and NO₂) with quasi continuousand global coverage in the period of MIPAS full spectral resolution mission.In this paper, we report a detailed description of the validation ofMIPAS-ENVISAT operational ozone data, that was based on the comparisonbetween MIPAS v4.61 (and, to a lesser extent, v4.62) O₃ VMR profilesand a comprehensive set of correlative data, including observations fromozone sondes, ground-based lidar, FTIR and microwave radiometers,remote-sensing and in situ instruments on-board stratospheric aircraft andballoons, concurrent satellite sensors and ozone fields assimilated by theEuropean Center for Medium-range Weather Forecasting.

A coordinated effort was carried out, using common criteria for the selectionof individual validation data sets, and similar methods for the comparisons.This enabled merging the individual results from a variety of independentreference measurements of proven quality (i.e. well characterized errorbudget) into an overall evaluation of MIPAS O₃ data quality, havingboth statistical strength and the widest spatial and temporal coverage.Collocated measurements from ozone sondes and ground-based lidar andmicrowave radiometers of the Network for the Detection AtmosphericComposition Change (NDACC) were selected to carry out comparisons with timeseries of MIPAS O₃ partial columns and to identify groups of stationsand time periods with a uniform pattern of ozone differences, that weresubsequently used for a vertically resolved statistical analysis. The resultsof the comparison are classified according to synoptic and regional systemsand to altitude intervals, showing a generally good agreement within thecomparison error bars in the upper and middle stratosphere. Significantdifferences emerge in the lower stratosphere and are only partly explained bythe larger contributions of horizontal and vertical smoothing differences andof collocation errors to the total uncertainty. Further results obtained froma purely statistical analysis of the same data set from NDACC ground-basedlidar stations, as well as from additional ozone soundings at middlelatitudes and from NDACC ground-based FTIR measurements, confirm the validityof MIPAS O₃ profiles down to the lower stratosphere, with evidence oflarger discrepancies at the lowest altitudes. The validation againstO₃ VMR profiles using collocated observations performed by othersatellite sensors (SAGE II, POAM III, ODIN-SMR, ACE-FTS, HALOE, GOME) andECMWF assimilated ozone fields leads to consistent results, that are to agreat extent compatible with those obtained from the comparison withground-based measurements. Excellent agreement in the full vertical range ofthe compar

[学科分类] 大气科学