1D+3DVar assimilation of radar reflectivity data: a proof of concept

Article English OPEN
Caumont, Olivier ; Ducrocq, Véronique ; Wattrelot, Éric ; Jaubert, Geneviève ; Pradier-Vabre, Stéphanie (2010)

An original one-dimensional (1-D) retrieval followed by a three-dimensional variational (1D+3DVar) assimilation technique is being developed to assimilate volumes of radar reflectivity data in the high-resolution numerical weather prediction Arome model. The good performance of the 1-D retrieval is shown for an isolated storm over southwestern France through an observing system simulation experiment. The full method is applied with real data to a flash-flood event, which occurred in a mountainous area. For this complex case, the assimilation of reflectivity data improves short-term precipitation forecasts. The assimilation of reflectivity data has a positive impact on the convective system’s dynamics by feeding the cold pool under the storm, which controls the intensity and location of the updrafts. A one-hourly update cycle of 3 h further improves these results. A sensitivity study is also presented to evaluate the assimilation method for this flash-flood event in different conditions. The smoothing coefficient involved in the 1-D retrieval is shown to have a very small impact on analyses and quantitative precipitation forecasts. The assimilation of reflectivity data is found to be able to cause the creation of a cold pool, which modifies favourably the precipitation quantitative forecast. Finally, results from an 8-d-long assimilation cycle are presented.
  • References (41)
    41 references, page 1 of 5

    Arnold, C. P. Jr., and Dey, C. H. 1986. Observing-systems simulation experiments: past, present, and future. Bull. Am. Meteor. Soc. 67(6), 687-695. doi:10.1175/1520-0477(1986)067< 0687:OSSEPP>2.0.CO;2.

    Berre, L. 2000. Estimation of synoptic and mesoscale forecast error covariances in a limited-area model. Mon. Wea. Rev. 128(3), 644-667. doi:10.1175/1520-0493(2000)128<0644:EOSAMF>2.0.CO;2.

    Bielli, S. and Roux, F. 1999. Initialization of a cloud-resolving model with airborne Doppler radar observations of an oceanic tropical convective system. Mon. Wea. Rev. 127(6), 1038-1055. doi:10.1175/1520-0493(1999)127<1038:IOACRM>2.0.CO;2.

    Bouttier, F. 2003. The AROME mesoscale project, Proceedings of the 2003 ECMWF Seminar on Recent Developments in Data Assimilation for Atmosphere and Ocean, Reading, United Kingdom. http://www.ecmwf.int/publications/library/do/references/show?id= 86068.

    Bouttier, F. 2007. Arome, avenir de la pre´vision re´gionale (Arome, a next fine-scale numerical weather prediction model). La Me´te´orologie 58, 12-20 (in French).

    Caumont, O., Ducrocq, V., Delrieu, G., Gosset, M., Parent du Chaˆtelet, J. and co-authors. 2006. A radar simulator for high-resolution nonhydrostatic models. J. Atmos. Oceanic Technol. 23(8), 1049-1067. doi:10.1175/JTECH1905.1.

    Chancibault, K., Anquetin, S., Ducrocq, V. and Saulnier, G.-M. 2006. Hydrological evaluation of high-resolution precipitation forecast of the Gard flash-flood event (8-9 September 2002). Quart. J. Roy. Meteor. Soc. 132, 1091-1117. doi:10.1256/qj.04.164.

    Delrieu, G., Creutin, J.-D. and Andrieu, H. 1995. Simulation of radar mountain returns using a digitized terrain model. J. Atmos. Oceanic Technol. 12(5), 1038-1049. doi:10.1175/1520- 0426(1995)012<1038:SORMRU>2.0.CO;2.

    Delrieu, G., Ducrocq, V., Gaume, E´., Nicol, J., Payrastre, O. and coauthors. 2005. The catastrophic flash-flood event of 8-9 September 2002 in the Gard region, France: a first case study for the Ce´vennes-Vivarais Mediterranean Hydrometeorological Observatory. J. Hydrometeor. 6(1), 34-52. doi:10.1175/JHM-400.1.

    Ducrocq, V., Lafore, J.-P., Redelsperger, J.-L. and Orain, F. 2000. Initialization of a fine-scale model for convective-system prediction: a case study. Quart. J. Roy. Meteor. Soc. 126(570), 3041-3065. doi:10.1002/qj.49712657004.

  • Metrics
    No metrics available
Share - Bookmark