Advances in Geosciences www.adv-geosci.net 1680-7340 1680-7359 16 Observation, Prediction and Verification of Precipitation (EGU Session 2007) 2008 10.5194/adgeo-16-73-2008 http://www.adv-geosci.net/16/73/2008/ http://www.adv-geosci.net/16/73/2008/adgeo-16-73-2008.html http://www.adv-geosci.net/16/73/2008/adgeo-16-73-2008.pdf 73 80 2008-04-09 The flood event that affected Badajoz in November 1997 P. Lorente pablo_lorente@fis.ucm.es E. Hernández S. Queralt P. Ribera Dept. de Física de la Tierra II, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, Spain Dept. de Física de la Tierra, Facultad de Ciencias Ambientales, Universidad Pablo de Olavide, Sevilla, Spain The flooding episode of November 1997 in Badajoz was one of the most dramatic catastrophes in Spain: as a result, there were 21 fatalities and huge financial damages. The main purpose of this work is to assess the prevailing synoptic conditions as well as detailing the mesoscale effects by means of moisture sources and dynamic and thermodynamic instability analysis involved in the November 1997 Spanish severe weather episode. In order to achieve the above, this flood event is described in terms of moisture content evolution by means of individual particle simulation along 3-day back-trajectories. A Lagrangian model is applied in order to characterize the atmospheric particles involved in the focused case (localization, height and specific humidity) which give rise to sudden precipitation stream. Geopotential height and temperature fields were used to describe the synoptic situation. Thermodynamic indices, such as CAPE, SWEAT and KI, and dynamic parameters like potential vorticity anomaly at 330 K isentropic surface and Q vector divergence were also calculated in order to complete the analysis and to give a thorough weather frame taking into account the atmospheric instability. The results of this work suggest this flood event was due mainly to strong dynamic instability along with large amounts of moisture advected by a trough, while the thermodynamic instability played a secondary role. Finally, a new methodology based on a technique proposed by Tremblay (2005) has been developed in order to separate the precipitation into stratiform and convective components. It is evident that the event was associated with a predominant convective regime. Houze, R. A.: Cloud Dynamics, Internatonal Geophysics Series, Vol 53, Academic Press, 573 pp., 1993. Houze, R. A.: Stratiform precipitation in regions of convection: A meteorological paradox?, B. Am. Meteorol. Soc., 78, 2179–2196, 1997. Jusem, J. C. and Atlas, R.: Diagnostic evaluation of vertical motion forcing mechanisms by using Q-vector partitioning, Mon. Weather Rev., 126, 2166–2184, 1997. Lang, S., Tao, W. K., Simpson, J., and Ferrier, B.: Modeling of convective – stratiform precipitation processes: Sensivity to partitioning methods, J. Appl. Meteor., 42, 505–527, 2003. Rodríguez-Puebla, C., Encinas, A. H., Nieto, S., and Garmendia, J.: Spatial and temporal patterns of annual precipitation variability over the Iberian peninsula. Int. J. Climatol., 18, 299–316, 1998. Rodríguez-Puebla, C., Encinas, A. H. and Sáenz, J.: Winter precipitation over the Iberian peninsula and its relationship to circulation indices, Hydrol. Earth Sy. Sci., 5, 233–244, 2001. Rogers, R. R. and Yau, M. K.: A short course in cloud physics, Pergamon Press, 196–205, 1989. Stohl, A., Hittenberger, M., and Wotawa, G.: Validation of the Lagrangian particle dispersion model FLEXPART against large scale tracer experiment data, Atmos. Environ., 32, 4245–4264, 1998. Stohl, A., and Thompson, D. J.: A density correction for Lagrangian particle dispersion models, Bound.-Layer Meteor., 90, 155–167, 1999. Tremblay, A.: The stratiform and convective components of surface precipitation, J. Atmos. Sci., 62, 1513–1528, 2005. Trenberth, K. E., Dai, A., Rasmussen, R.M., and Pearson, D.: The changing character of precipitation, B. Am. Meteorol. Soc., 84, 1205–1217, 2003. Wallace, J. M. and Gutzler, D. S.: Teleconnection in the geopotential height field during the Northern Hemisphere winter, Mon. Weather Rev., 109, 784–812, 1981.