Atmos. Chem. Phys. Discuss., 13, 4433-4489, 2013
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Validation of MIPAS-ENVISAT H2O operational data collected between July 2002 and March 2004
G. Wetzel1, H. Oelhaf1, G. Berthet2, A. Bracher3,*, C. Cornacchia4, D. G. Feist5, H. Fischer1, A. Fix6, M. Iarlori7, A. Kleinert1, A. Lengel1,**, M. Milz8, L. Mona4, S. C. Müller9,***, J. Ovarlez2, G. Pappalardo4, C. Piccolo10,****, P. Raspollini10, J.-B. Renard2, V. Rizi7, S. Rohs11, C. Schiller11,†, G. Stiller1, M. Weber3, and G. Zhang1
1Institute for Meteorology and Climate Research (IMK), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
2Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), CNRS, Orléans, France
3Institute of Environmental Physics and Remote Sensing (IUP/IFE), University of Bremen, Bremen, Germany
4CNR-IMAA, Consiglio Nazionale delle Ricerche – Istituto di Metodologie per l'Analisi Ambientale, Tito Scalo, Potenza, Italy
5Max Planck Institute for Biogeochemistry, Jena, Germany
6Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
7CETEMPS – Dipartimento di Scienze Fisiche e Chimiche – Università degli Studi, L'Aquila, Italy
8Department of Computer science, Electrical and Space engineering, Luleå University of Technology, Kiruna, Sweden
9Institute of Applied Physics (IAP), University of Bern, Bern, Switzerland
10Istituto di Fisica Applicata "Nello Carrara" (IFAC), del Consiglio Nazionale delle Ricerche (CNR), Firenze, Italy
11Institute for Energy and Climate Research – Stratosphere (IEK-7), Forschungszentrum Jülich, Jülich, Germany
*now at: Alfred Wegener Institute (AWI), Bremerhaven, Germany
**now at: Carl Zeiss AG, Oberkochen, Germany
***now at: METEOTEST, Bern, Switzerland
****now at: Met Office, Exeter, UK

Abstract. Water vapour (H2O) is one of the operationally retrieved key species of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument aboard the environmental satellite ENVISAT which was launched into its sun-synchronous orbit on 1 March 2002 and operated until April 2012. Within the MIPAS validation activities, independent observations from balloons, aircraft, satellites, and ground-based stations have been compared to European Space Agency (ESA) version 4.61 operational H2O data comprising the time period from July 2002 until March 2004 where MIPAS measured with full spectral resolution. No significant bias in the MIPAS H2O data is obvious in the lower stratosphere (above the hygropause) between about 15 and 30 km. Differences of H2O quantities observed by MIPAS and the validation instruments are mostly well within the combined total errors in this altitude region. In the upper stratosphere (above about 30 km), a tendency towards a small positive bias (up to 10%) is present in the MIPAS data when compared to its balloon-borne counterpart MIPAS-B, to the satellite instruments HALOE (Halogen Occultation Experiment) and ACE-FTS (Atmospheric Chemistry Experiment, Fourier Transform Spectrometer), and to the MM-wave airborne sensor AMSOS (Airborne Microwave Stratospheric Observing System). In the mesosphere the situation is unclear due to the occurrence of different biases when comparing HALOE and ACE-FTS data. Pronounced deviations between MIPAS and the correlative instruments occur in the lowermost stratosphere and upper troposphere, a region where retrievals of H2O are most challenging. Altogether it can be concluded that MIPAS H2O profiles yield valuable information on the vertical distribution of H2O in the stratosphere with an overall accuracy of about 10 to 30% and a precision of typically 5 to 15% – well within the predicted error budget, proving that these global and continuous data are very valuable for scientific studies. However, in the region around the tropopause retrieved MIPAS H2O profiles are less reliable, suffering from a number of obstacles such as retrieval boundary and cloud effects, sharp vertical discontinuities, and frequent horizontal gradients in both temperature and H2O volume mixing ratio (VMR). Some profiles are characterized by retrieval instabilities.

Citation: Wetzel, G., Oelhaf, H., Berthet, G., Bracher, A., Cornacchia, C., Feist, D. G., Fischer, H., Fix, A., Iarlori, M., Kleinert, A., Lengel, A., Milz, M., Mona, L., Müller, S. C., Ovarlez, J., Pappalardo, G., Piccolo, C., Raspollini, P., Renard, J.-B., Rizi, V., Rohs, S., Schiller, C., Stiller, G., Weber, M., and Zhang, G.: Validation of MIPAS-ENVISAT H2O operational data collected between July 2002 and March 2004, Atmos. Chem. Phys. Discuss., 13, 4433-4489, doi:10.5194/acpd-13-4433-2013, 2013.
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