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https://doi.org/10.5194/amt-2017-374
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
26 Oct 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Measurement Techniques (AMT).
Evaluation of MUSICA MetOp/IASI tropospheric water vapour profiles by theoretical error assessments and comparisons to GRUAN Vaisala RS92 measurements
Christian Borger1,a, Matthias Schneider1, Benjamin Ertl1,2, Frank Hase1, Omaira E. García3, Michael Sommer4, Michael Höpfner1, Stephen A. Tjemkes5, and Xavier Calbet6 1Institute of Meteorology and Climate Research (IMK-ASF), Karlsruhe Institute of Technology, Karlsruhe, Germany
2Steinbuch Centre for Computing (SCC), Karlsruhe Institute of Technology, Karlsruhe, Germany
3Izaña Atmospheric Research Center, Agencia Estatal de Meteorología (AEMET), Santa Cruz de Tenerife, Spain
4Deutscher Wetterdienst, Meteorologisches Observatorium Lindenberg, Richard-Aßmann-Observatorium, Am Observatorium 12, 15848, Lindenberg/Tauche, Germany
5EUMETSAT, Eumetsat Allee 1, 64295 Darmstadt, Germany
6AEMET, C/Leonardo Prieto Castro 8, Ciudad Universitaria, 28071 Madrid, Spain
anow at: Satellite Remote Sensing Group, Max Planck Institute for Chemistry, Mainz, Germany
Abstract. Volume mixing ratio water vapour profiles have been retrieved from IASI (Infrared Atmospheric Sounding Interferometer) spectra by using the MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) processor. The retrievals are made for IASI observations that coincide with Vaisala RS92 radiosonde measurements performed in the framework of the GCOS (Global Climate Observing System) Reference Upper-Air Network (GRUAN) in three different climate zones: the tropics (Manus Island, 2° S), mid-latitudes (Lindenberg, 52° N) and polar regions (Sodankylä, 67° N).

The retrievals show good sensitivity with respect to the vertical H2O distribution between 1–2 km above ground and the upper troposphere. Typical DOFS (degree of freedom for signal) values are about 5.5 for the tropics, 5.0 for summertime midlatitudes, 4.0 for wintertime mid-latitudes, and 4.5 for summertime polar regions. The errors of the IASI water vapour profiles have been theoretically estimated considering the contribution of a large number of uncertainty sources. For all three climate regions unrecognized cirrus clouds and uncertainties in atmospheric temperature have been identified as the most important error sources, whereby the total errors are estimated to be typically 25 %.

The IASI water vapour profiles have been compared to 100 individual coinciding GRUAN water vapour profiles. The systematic difference between the IASI and GRUAN data is within 12 % at all altitudes. The scatter is largest close to the surface and close to the tropopause, but does never exceed 30 %. The study documents that the MUSICA MetOp/IASI retrieval processor provides H2O profiles with good accuracy and captures the variations in H2O volume mixing ratio profiles from 1–2 km above ground up to altitudes close to the tropopause with a precision that is in accordance to the theoretical error assessment.


Citation: Borger, C., Schneider, M., Ertl, B., Hase, F., García, O. E., Sommer, M., Höpfner, M., Tjemkes, S. A., and Calbet, X.: Evaluation of MUSICA MetOp/IASI tropospheric water vapour profiles by theoretical error assessments and comparisons to GRUAN Vaisala RS92 measurements, Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2017-374, in review, 2017.
Christian Borger et al.
Christian Borger et al.
Christian Borger et al.

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Short summary
MUSICA MetOp/IASI tropospheric water vapour profile retrievals are evaluated by performing theoretical error assessments and comparisons to GRUAN radiosonde measurements. We show that the vertical water vapour distribution is well captured between 1–2 km above ground and the upper troposphere. Most important error sources are unrecognized clouds and uncertainties in atmospheric temperature. Total errors reach about 25 %.
MUSICA MetOp/IASI tropospheric water vapour profile retrievals are evaluated by performing...
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