HYMEX-SOP1 the Field Campaign Dedicated to Heavy Precipitation and Flash Flooding in the Northwestern Mediterranean
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HYMEX-SOP1 The Field Campaign Dedicated to Heavy Precipitation and Flash Flooding in the Northwestern Mediterranean BY VÉRONIQUE DUCROCQ, ISABELLE BRAUD, SILVIO DAVOLIO, ROSSELLA FERRETTI, CYRILLE FLAMANT, AGUSTIN JANSA, NORBERT KALTHOff, EVELYNE RICHARD, ISABELLE TAUPIER-LETAGE, PIERRE-ALAIN AYRAL, SOPHIE BELAMARI, ALEXIS BERNE, MARCO BORGA, BRICE BOUDEVILLAIN, OLIVIER BOCK, JEAN-LUC BOICHARD, MARIE-NOËLLE BOUIN, OLIVIER BOUSQUET, CHRISTOPHE BOUVIER, JACOPO CHIGGIATO, DOMENICO CIMINI, ULRICH CORSMEIER, LAURENT COPPOLA, PHILIPPE COCQUEREZ, ERIC DEFER, JULIEN DELANOË, PAOLO DI GIROLAMO, ALEXIS DOERENBECHER, PHILIPPE DROBINSKI, YANN DUFOURNET, NADIA FOURRIÉ, JONATHAN J. GOURLEY, LAURENT LABATUT, DOMINIQUE LAMBERT, JÉRÔME LE COZ, FRANK S. MARZANO, GILLES MOLINIÉ, ANDREA MONTANI, GUILLAUME NORD, MATHIEU NURET, KARIM RAMAGE, WILLIAM RISON, ODILE ROUSSOT, FRÉDÉRIQUE SAID, ALFONS SCHWARZENBOECK, PIERRE TESTOR, JOËL VAN BAELEN, BÉATRICE VINCENDON, MONTSERRAT ARAN, AND JORGE TAMAYO HyMeX-SOP1 collected unprecedented observations of atmosphere, ocean, land, and rivers to improve the knowledge and prediction of the most damaging natural hazards in the Mediterranean. he distinctive topography and geographical location of the T Mediterranean basin (Fig. 1) make the region prone to heavy precipitation and flash floods. Most of these events occur in autumn (September–November) over the western Mediterranean. The Mediterranean Sea acts as a vast heat and moisture source from which convective and baroclinic atmo- spheric systems derive their energy. The steep orography surrounding the Mediterranean Sea aids in lifting the low-level, conditionally unstable FIG. 1. The western Mediterranean region together with the HyMeX air, thus initiating condensation and sites: the Balearic Islands (BA), Catalonia (CA), and Valencia (VA) convection processes. Daily surface regions in Spain; Cévennes-Vivarais (CV) and Corsica (CO) in France; rainfall greater than 100 mm is not and central Italy (CI), Liguria-Tuscany (LT), and northeastern Italy uncommon for Mediterranean pre- (NEI) in Italy. Only sites delineated with red lines hosted research cipitation events. The coincidence of ground instruments. Note that the CV site includes not only the these heavy precipitation amounts Cévennes-Vivarais mountain range (Massif Central) but also the superimposed on small and steep French southern Alps. AMERICAN METEOROLOGICAL SOCIETY JULY 2014 | 1083 Unauthenticated | Downloaded 10/08/21 04:44 AM UTC river catchments characteristic of the Mediterra- the water cycle in the Mediterranean with a strong nean basin often induces devastating flash floods emphasis on high-impact weather events (Drobinski and flooding events. Each year, these events result et al. 2014). A key component of this program is its in up to hundreds of millions of euros in damages first field experiment, also called the special observa- and often casualties (e.g., Llasat et al. 2013; Munich tion period (SOP1), dedicated to heavy precipitation RE 2011, 2012). Considerable efforts to improve the and flash floods in northwestern Mediterranean. skill of the forecasts for such severe events have been This article provides the rationale for developing made in recent years and significant progress has this field experiment and general information on the been realized through the development of convection- design and operations of this field campaign. Three permitting numerical weather prediction (NWP) intensive observation periods (IOPs) are highlighted systems. However, the accuracy of forecasts is still here to demonstrate the value of the SOP1 observation insufficient to satisfy the societal demands in terms strategy for process understanding, model improve- of amount, timing, and basin-specific locations of ment, and data assimilation. rainfall and flash flooding. Our ability to predict such high-impact events remains limited because of SCIENCE ISSUES. Heavy precipitation events the influence of finescale processes (e.g., convection, (HPEs) in the Mediterranean are characterized by turbulence, microphysics) and their nonlinear inter- rainfall accumulations generally greater than 100 mm actions with larger-scale processes. Advances in the recorded in less than a day and often within just a few identification of the predominant mechanisms, and hours. These intense rainfall amounts typically come particularly of their interactions across scales, are from quasi-stationary mesoscale convective systems mandatory in order to better forecast these events. (MCSs). For instance, MCSs were responsible for the The Hydrological Cycle in the Mediterranean rainfall that led to the dramatic flash-flood events Experiment (HyMeX) offers a unique opportunity in Vaison-la-Romaine in September 1992 (300 mm to improve our capabilities to predict these high- in 4 h; Sénési et al. 1996), Liguria in October and impact weather events. Major goals of the program November 2011 (450–500 mm in 6–12 h; Silvestro include better quantification and understanding of et al. 2012; Rebora et al. 2013), Gard in September AFFILIATIONS: DUCROCQ, BELAMARI, BOUSQUET, DOERENBECHER, de Villefranche-sur-mer, France; COCQUEREZ—Centre National FOURRIÉ, LABATUT, NURET, ROUSSOT, AND VINCENDON—CNRM-GAME, d’Etudes Spatiales, Toulouse, France; DEFER—LERMA, Observatoire Météo-France/CNRS, Toulouse, France; BRAUD AND LE COZ— de Paris, Paris, France; DI GIROLAMO—Scuola di Ingegneria, IRSTEA, UR HHLY Unité de Recherche Hydrologie-Hydraulique, Università degli Studi della Basilicata, Potenza, Italy; DROBINSKI— Lyon, France; DAVOLIO—Institute of Atmospheric Sciences LMD/IPSL, CNRS/Ecole Polytechnique, Palaiseau, France; and Climate, CNR-ISAC, Bologna, Italy; FERRETTI—CETEMPS, DUFOURNET—Delft University of Technology–Climate Institute, The Department of Physical Science and Chemistry, Università Netherlands; GOURLEY—NOAA/National Severe Storms Labora- dell’Aquila, L’Aquila, Italy; FLAMANT AND DELANOË—LATMOS, tory, Norman, Oklahoma; MARZANO—DIET, Sapienza, University UMR 8190 CNRS-UVSQ-UPMC, Guyancourt, France; JANSA AND of Rome, Rome, and CETEMPS, Department of Physical Science TAMAYO—Agencia Estatal de Meteorología, Madrid, Spain; KALTHOff and Chemistry, Università dell’Aquila, L’Aquila, Italy; MONTANI— AND CORSMEIER—Karlsruhe Institute of Technology, IMK-TRO, ARPA-SIMC, Bologna, Italy; RAMAGE—IPSL, Palaiseau, France; Karlsruhe, Germany; RICHARD, LAMBERT, AND SAID—Laboratoire RISON—New Mexico Tech, Socorro, New Mexico; SCHWARZENBOECK d’Aérologie, Université de Toulouse/CNRS 5560, Toulouse, France; AND VAN BAELEN—Laboratoire de Météorologie Physique (LaMP), TAUPIER-LETAGE—MIO, AMU UM110, CNRS UMR 7294, IRD UMR UMR6016, UBP and CNRS, Clermont-Ferrand, France; TESTOR— 235, USTV, Marseille, France; AYRAL—Ecole des Mines d’Ales and LOCEAN/IPSL, Paris, France; ARAN—Servei Meteorològic de UMR 7300 ESPACE CNRS, Université de Nice-Sophia-Antipolis, Catalunya (SMC), Spain France; BERNE—Environmental Remote Sensing Laboratory, CORRESPONDING AUTHOR: Véronique Ducrocq, CNRM- École Polytechnique Fédérale de Lausanne, Switzerland; BORGA— GAME, UMR3589, Météo-France/CNRS,42 Av. Coriolis, 31 057 Department of Land, Environment, Agriculture and Forestry, Toulouse CEDEX, France University of Padova, Italy; BOUDEVILLAIN, MOLINIÉ, AND NORD— LTHE E-mail: [email protected] (UMR 5564 CNRS/IRD/Université de Grenoble), Grenoble, France; The abstract for this article can be found in this issue, following the table BOCK—Laboratoire de Recherche en Géodésie (LAREG), IGN, of contents. Marne la Vallée, France; BOICHARD—Observatoire Midi-Pyrénées, DOI:10.1175/BAMS-D-12-00244.1 Toulouse, France; BOUIN—CNRM/CMM, Météo-France, Brest, France; BOUVIER—Hydrosciences Montpellier, Montpellier, France; A supplement to this article is available online (10.1175/BAMS-D-12-00244.2) CHIGGIATO—CNR-ISMAR, Venezia, Italy; CIMINI—CNR-IMAA, In final form 5 September 2013 Tito Scalo, Potenza, Italy; COPPOLA—Observatoire Océanologique ©2014 American Meteorological Society 1084 | JULY 2014 Unauthenticated | Downloaded 10/08/21 04:44 AM UTC 2002 (about 700 mm in 24 h; Delrieu et al. 2005), location as long as the flux of low-level moisture and Valencia in November 1987 (more than 800 mm remains intact. However, orographic precipitation in 24 h; Romero et al. 2000). These storm systems associated with conditional convective instability is are generally back-building quasi-stationary MCSs very sensitive to a number of factors related to cloud (Bluestein and Jain 1985), with a V-shaped anvil microphysical processes and to the complexity of (or plume) identified in the infrared satellite im- the orography itself (Miglietta and Rotunno 2009, ages. Back-building results from renewed convective 2010). Furthermore, coastal mountains are not the development at the vertex of the V, which faces the only sources of lifting. Mountains and islands in the low-level marine flow. Mediterranean alter the low-level circulation over the The synoptic-scale patterns associated with sea (e.g., lee cyclones, channeling, and wake effects), HPEs are characteristic of Rossby wave breaking at frequently generating low-level convergence responsi- the eastern end of the North Atlantic storm track. ble for convective initiation (Buzzi and Foschini 2000; An upper-level low northwest of the impacted area, Jansa et al. 2001; Davolio et al. 2009). Frontal lifting possibly associated with a warm conveyor belt, helps associated with quasi-stationary frontal systems to generate low-level marine flow directed northward may also help the