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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union

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https://doi.org/10.5194/amt-2017-377
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
23 Nov 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Measurement Techniques (AMT).
All-sky Information Content Analysis for Novel Passive Microwave Instruments in the Range from 23.8 GHz up to 874.4 GHz
Verena Grützun1, Stefan A. Buehler1, Lukas Kluft2, Jana Mendrok3, Manfred Brath1, and Patrick Eriksson3 1Meteorologisches Institut, Fachbereich Geowissenschaften, Centrum für Erdsystem- und Nachhaltigkeitsforschung (CEN), Universität Hamburg, Bundesstraße 55, 20146 Hamburg, Germany
2Max-Planck-Institut für Meteorologie, Hamburg, Germany
3Department of Space, Earth and Environment, Chalmers University of Technology, 41296 Gothenburg, Sweden
Abstract. We perform an all-sky information content analysis for channels in the millimeter/submillimeter wavelength with 24 channels in the region from 23.8 up to 874.4 GHz. Our set of channels corresponds to the instruments ISMAR and MARSS, which are available on the British FAAM research aircraft, and it is complemented by two precipitation channels at low frequencies from Deimos. The channels also cover ICI, which will be part of the MetOp-SG mission. We use simulated atmospheres from the ICON model as basis for the study and quantify the information content with the reduction of degrees of freedom (ΔDOF). The required Jacobians are calculated with the radiative transfer model ARTS. Specifically we focus on the dependence of the information content on the atmospheric composition. In general we find a high information content for the frozen hydrometeors, which mainly comes from the higher channels beyond 183.31 GHz (on average 4.99 for cloud ice and 4.84 for snow). Profile retrievals may be possible for the mass densities and some information about the microphysical properties, especially for cloud ice, can be gained. The information about the liquid hydrometeors comes from the lower channels and is comparably low (2.36 for liquid cloud water and 1.81 for rain). There is little information about the profile or the microphysical properties. The Jacobians for a specific cloud hydrometeor strongly depend on the atmospheric composition. Especially for the liquid hydrometeors they even change sign in some cases. However, the information content is robust. For liquid hydrometeors it slightly decreases in the presence of any frozen hydrometeor, for the frozen hydrometeors it slightly decreases in the presence of the respective other frozen hydrometeor. The overall results with regard to the frozen hydrometeors in principle also hold for the ICI sensor. This points to its great ability to observe ice clouds from space on a global scale with a good spatial coverage in unprecedented detail.

Citation: Grützun, V., Buehler, S. A., Kluft, L., Mendrok, J., Brath, M., and Eriksson, P.: All-sky Information Content Analysis for Novel Passive Microwave Instruments in the Range from 23.8 GHz up to 874.4 GHz, Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2017-377, in review, 2017.
Verena Grützun et al.
Verena Grützun et al.
Verena Grützun et al.

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Short summary
The global observation of ice clouds is crucial because they are important factors in the climate system but still are amongst the greatest uncertainties for estimating the Earth's energy budget in a changing climate. Reliable global long-term measurements are, however, scarce. At the hand of atmospheric model data from the ICON model in combination with the radiative transfer simulator ARTS we explore the potential of passive millimeter/sub-millimeter wavelength measurements to fill that gap.
The global observation of ice clouds is crucial because they are important factors in the...
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