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-16-81-2008 http://www.adv-geosci.net/16/81/2008/ http://www.adv-geosci.net/16/81/2008/adgeo-16-81-2008.html http://www.adv-geosci.net/16/81/2008/adgeo-16-81-2008.pdf 81 88 2008-04-09 Mesoscale convective systems in Spain: instability conditions and moisture sources involved S. Queralt queralt@fis.ucm.es E. Hernandez D. Gallego P. Lorente Universidad Complutense de Madrid, Madrid, Spain Universidad Pablo de Olavide, Sevilla, Spain Source-receptor water vapor content areas are analyzed for a particular case of deep mesoscale convective system (MCS) developed over the Mediterranean margin of Spain in October 1982. The aim of this work is to study simultaneously the atmospheric instability conditions and water vapour fluxes which finally resulted in very severe precipitation rates, reaching up to 600 mm in a single day. Humidity amounts and transport are quantified along the trajectories computed from a lagrangian particle simulation model (FLEXPART6.2). To evaluate the precipitation probability, the water vapor content and both thermodynamic and dynamic atmospheric instability components were assessed. The October 1982 Iberian MCS occurred as a consequence of a deep cutoff low detected between 500 and 200 hPa levels. The dynamical instability was measured through potential vorticity anomalies and Q vector divergence, which presented their maximum and minimum centers respectively over south-eastern Iberia. Synoptic and dynamic instability conditions were obtained from the ERA-40 reanalysis dataset. It is observed that during this severe weather episode, the specific humidity increased along the lowest and easternmost trajectories, which are mainly spread over the Mediterranean Sea. Gallego, D., Ribera, P., García-Herrera, R., Hernández, E., and Gimeno, L.: A new look for the Southern Hemisphere jet stream, Clim. Dynam., 24, 607–621, 2005. García-Herrera, R., Hernández, E., Paredes, D., Barriopedro, D., Correoso, J. F., and Prieto, L.: A MASCOTTE-based characterization of MCSs over Spain, 2000–2002, Atmos. Res., 73, 261–282, 2005. García-Herrera, R., Barriopedro, D., Hernández D., Paredes, D., Correoso, J. F., and Prieto, L.: The 2001 Mesoscale Convective Systems over Iberia and Balearic Islands, Meteorol. Atmos. Phys., 90, 225–243, 2005. Hoskins, B. J., Draghici, I., and Davies, H. C.: A new look at the $\omega $ equation, Quart. J. R. Meteorol. Soc., 104, 31–38, 1978. Hoskins, B. J., McIntyre, M. E., and Robertson, A. W.: On the use and significance of isentropic potential vorticity maps, Quart. J. R. Meteorol. Soc., 111, 877–946, 1985. James, P., Stohl, A., Spichtinger, N., Eckhardt, S., and Foster, C.: Climatological aspects of the extreme European rainfall of August 2002 and a trajectory method for estimating the associated evaporative source regions. Nat. Hazards Earth Syst. Sci., 4, 733–746, 2004. Lamarque, J. F. and Hess, P. G.: Cross-Tropopause Mass Exchange and Potential Vorticity Budget in a Simulated Tropopause Folding, J. Atmos. Sci., 51(15), 2246–2269, 1994. Nieto, R., Gimeno, L., de la Torre, L., Ribera, P., Gallego, D., García-Herrera, R., García, J. A., N\'uñez, M., Redaño A., and Lorente, J.: Climatological features of Cut-off Low Systems in the Northern Hemisphere, J. Climate, 18, 3085–3103, 2005. Paredes, D., Trigo, R. M., Garcia-Herrera, R., and Franco, I.: Understanding Precipitation Changes in Iberia in Early Spring: Weather Typing and Store-Tracking Approaches, J. Hydrometeorol., 7, 101–113, 2006. Romero, R., Doswell, C. A., and Ramis, C.: Mesoscale Numerical Study of Two Cases of Long-Lived Quasi-Stationary Convective Systems over Eastern Spain, Mon. Weather Rev., 128, 3731–3750, 2000. Sprenger, M., Wernli, H., and Bourqui, M.: Stratosphere-Troposphere Exchange and its Relation to Potential Vorticity Streamers and Cutoffs near the Extratropical Tropopause, J. Atmos. Res., 64, 1587–1602, 2007. Stohl A. and James, P.: A Lagrangian Analysis of the Atmospheric Branch of the Global Water Cycle, Part I: Method Description, Validation, and Demonstration for the August 2002 Flooding in Central Europe, J. Hydrometeorol., 5(4), 656–678, 2004. Stohl A. and James, P.: A Lagrangian Analysis of the Atmospheric Branch of the Global Water Cycle, Part II: Moisture Transports between Earth's Ocean Basins and River Catchments, J. Hydrometeorol., 6(6), 961–984, 2005. Trigo, R. M. and DaCamara, C.: Circulation Weather Types and their Influence on the Precipitation Regime in Portugal, Int. J. Climatol., 20, 1559–1581, 2000.