Assimilation and Process Studies for selected COPS IOPs using GPS STD and radar radial velocities in the WRF-Var system (APRO-GRAVAR)
Final Report Abstract
This work applies observations of the field experiment COPS where GFZ collected a unique, real-time GPS data set (slant total delay (STD), zenith total delay (ZTD), integrated water vapor (IWV)), which was re-processed and extended. Furthermore, radar radial velocities from the German and French radar networks as well as in-situ observations from the ECMWF MARS archive complemented by additional observations collected during COPS were included into the investigations. It was demonstrated by IPM that advanced data assimilation systems combined with the dense COPS data set were capable to construct accurate initial states, so that the evolution of the 4D thermodynamic state in complex terrain can be simulated in dependence on largescale forcing mechanisms. Particularly interesting are the formation of thermally induced upslope flows and mesoscale vortices. These are expected to play a key role for the formation of convergence lines and convection initiation. Furthermore, convection and its organization were investigated. Another key topic was the demonstration of the value of the highresolution observations for validation and model improvement purposes. Comparisons of high-resolution simulations and observations collected during COPS revealed systematic model errors. The work in the field of GPS meteorology was continued by validating the improved GPS processing strategies developed at the GFZ in the preceding COPS-GRID project. Extensive validation studies based on water vapor radiometers and analyses of numerical weather models (e.g. ECMWF) provided the error characteristics of the slant total delays. These results are not only required by the data assimilation studies described above but were also used to refine the processing algorithms. The stages of the GPS processing procedure were investigated separately in order to validate all quantities contributing to the slant total delay, e. g. the dry and wet zenith delays, the atmospheric gradients and the residuals. The required observations were taken from the COPS database, the COPS-COSMO-reanalysis carried out by the DWD and ECMWF data. The near real-time data processing and the reprocessing of the COPS GPS data set was continued to extend the GPS networks and to provide most reliable GPS observations processed with the latest version of the GFZ EPOS processing software. The results demonstrated that slant total delays provided by the GFZ GNSS processing systems contain valuable information about the spatial water vapor distribution in the atmosphere. The STD validation studies show that GNSS STDs and similar observations from other observation systems correspond within the errors of both systems.
Publications
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2011: High-resolution simulation over central Europe: Assimilation experiments with WRF 3DVAR during COPS IOP9c. Q. J. R. Meteorol. Soc. 137, 156-175
Schwitalla, T., H.-S. Bauer, V. Wulfmeyer, and F. Aoshima
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2011: Validation of tropospheric slant path delays derived from single and dual frequency GPS receivers, Radio Sci. 46, RS6007
Deng, Z., M. Bender, F. Zus, M. Ge, G. Dick, M. Ramatschi, J. Wickert, U. Löhnert, and S. Schön
