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Free Content Development and optimization of the IPM MM5 GPS slant path 4DVAR system

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This article describes the development of tools for routine 4-dimensional variational data assimilation of Global Positioning System Slant Total Delay (STD) data in the framework of the MM5 system at the Institute of Physics and Meteorology of the University of Hohenheim. The Slant Total Delay forward operator is introduced which allows model validation and the assimilation in the Message-Passing Interface environment. An experiment is conducted which highlights the importance of accurate model physics in the variational assimilation system. We demonstrate that the model minus observation statistics of STD data crucially depends on the convection scheme and the implementation of horizontal diffusion. A set of modifications to the existing non linear, tangent linear and adjoint model is presented. These include an improvement of the horizontal diffusion scheme and the implementation of the Grell cumulus convective scheme in order to eliminate the observed systematic tendency in the model minus observation statistics of the STD data and precipitation in mountainous terrain. A first assimilation experiment with the improved MM5 variational assimilation system shows promising results.

Dieser Artikel beschreibt die Entwicklung von Tools zur 4-dimensionalen variationellen Assimilation von Global Positioning System Slant Total Delay (STD) Daten mit dem MM5 System am Institut für Physik und Meteorologie der Univerität Hohenheim. Der Vorwärtsoperator wird vorgestellt, der Validationsstudien und die Assimilation in die Message-Passing Interface Umgebung des MM5 erlaubt. Wir demonstrieren, dass die Modell-minus-Beobachtung-Statistik der STD Daten entscheidend von dem verwendeten Konvektionsschema und der Implementierung der horizontalen Diffusion abhängt. Ein Satz von Modifikationen zum existierenden nicht-linearen, tangent-linearen und adjungierten Modell wird präsentiert. Ein verbessertes Schema der horizontalen Diffusion und die Implementierung des Konvektionsschemas von Grell sind notwendig, um die systematische Tendenz in der Modell-minus-Beobachtung-Statistik der STD Daten und des Niederschlags in komplexen Gelände zu vermeiden. Ein erstes Assimilationsexperiment zeigt vielversprechende Ergebnisse.

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Document Type: Research Article

Publication date: 01 December 2008

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  • Meteorologische Zeitschrift (originally founded in 1866) is the joint periodical of the meteorological societies of Austria, Germany and Switzerland. It accepts high-quality peer-reviewed manuscripts on all aspects of observational, theoretical and computational research out of the entire field of meteorology, including climatology. Meteorologische Zeitschrift represents a natural forum for the meteorological community of Central Europe and worldwide.
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