Journal cover Journal topic
Annales Geophysicae An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

IF value: 1.490
IF 5-year value: 1.445
IF 5-year
CiteScore value: 2.9
SNIP value: 0.789
IPP value: 1.48
SJR value: 0.74
Scimago H <br class='widget-line-break'>index value: 88
Scimago H
h5-index value: 21
Volume 27, issue 7
Ann. Geophys., 27, 2739–2753, 2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 27, 2739–2753, 2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  09 Jul 2009

09 Jul 2009

Impact of high-resolution data assimilation of GPS zenith delay on Mediterranean heavy rainfall forecasting

K. Boniface1, V. Ducrocq2, G. Jaubert2, X. Yan2, P. Brousseau2, F. Masson3, C. Champollion1, J. Chéry1, and E. Doerflinger1 K. Boniface et al.
  • 1Géosciences Montpellier, UMR 5243 CNRS-UM2, CC. 60, Place E. Bataillon, 34095 Montpellier Cedex 5, France
  • 2GAME-CNRM, CNRS-Météo-France, 42 Avenue Coriolis, 31057 Toulouse Cedex 1, France
  • 3UMR 7516-IPGS-CNRS-EOST, 5 rue René Descartes, 67084 Strasbourg Cedex, France

Abstract. Impact of GPS (Global Positioning System) data assimilation is assessed here using a high-resolution numerical weather prediction system at 2.5 km horizontal resolution. The Zenithal Tropospheric Delay (ZTD) GPS data from mesoscale networks are assimilated with the 3DVAR AROME data assimilation scheme. Data from more than 280 stations over the model domain have been assimilated during 15-day long assimilation cycles prior each of the two studied events. The results of these assimilation cycles show that the assimilation of GPS ZTD with the AROME system performs well in producing analyses closer to the ZTD observations in average.

Then the impacts of assimilating GPS data on the precipitation forecast have been evaluated. For the first case, only the AROME runs starting a few hours prior the triggering of the convective system are able to simulate the convective precipitation. The assimilation of GPS ZTD observations improves the simulation of the spatial extent of the precipitation, but slightly underestimates the heaviest precipitation in that case compared with the experiment without GPS. The accuracy of the precipitation forecast for the second case is much better. The analyses from the control assimilation cycle provide already a good description of the atmosphere state that cannot be further improved by the assimilation of GPS observations. Only for the latest day (22 November 2007), significant differences have been found between the two parallel cycles. In that case, the assimilation of GPS ZTD allows to improve the first 6 to 12 h of the precipitation forecast.

Publications Copernicus