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cnrs I international 16 On Location | Live from the Labs magazine Hydrometeorology HyMeX program scientists have launched a campaign to improve understanding of the Mediterranean region’s violent and devastating storms. BY vahé ter minassian From September 5 to November 6, 2012, some 300 scientists were mobilized across 8 regions of France, Spain, and Italy, along with three research aircraft, two ships, and a host of radars, lidars, and balloons. This extensive campaign, part of the Hydrological Cycle in the Mediterranean Experiment (HyMeX) program coordinated by CNRS and the French Met Office Météo-France, is expected to last ten years (2010-2020). HyMeX has already been funded for four years to the tune of €8 million. The program was initiated by GAME laboratory1 senior scientist Véronique Ducrocq and LMD2 senior researcher Philippe Drobinski, who coordinate it at the international level. This colossal operation brings together nine countries to address a crucial issue, that of “deciphering the water cycle in the Mediterranean to improve forecasting of hydrometeorological hazards such as heavy rainfall, flash floods, strong winds, and droughts.” Mediterranean Storm Chasers Indeed, a number of highly-localized weather events remain poorly understood by forecasters. Known as “Mediterranean episodes” or “Cévenol events,” they can have dramatic consequences, such as the floods that killed 800 people in Algeria in 2001, or the 1992 Vaison-la-Romaine disaster in France, which claimed 47 lives. The main causes of these phenomena, which mostly occur in late summer and early winter, are well known. At that time of year, when the first cold air arrives from the north, the sea is still warm and acts as a source of water vapor and energy. When marine air flows reach land, they are forced to lift above the coastal mountains, triggering thunderstorms. As long as masses of humid, unstable air blow in from the sea, storms are repeatedly generated at the same spot, leading to heavy precipitation, up to 500 mm (i.e., 500 l per square meter) in just a few hours. This can result in a rapid rise in river water levels, causing flooding, mudslides, and landslides. “However, we still lack information about the microphysics of the clouds that cause these storms, the ice crystals they contain, and the atmospheric conditions in which they form,” Ducrocq explains. And there are numerous other issues. How will Mediterranean events evolve in the future? Is it possible to forecast precisely when and where these events will occur? The researchers hope that the HyMeX campaign will provide answers to these questions. And that it will enable them to improve and test experimental climate and weather models, such as Météo-France’s AROME system, which should be able to calculate the probability of a hazard in France with a grid size of 2.5 km. 01. Groupe d’étude de l’atmosphère météorologique (CNRS / Météo-France). 02. Laboratoire de météorologie dynamique (CNRS / ENS / UPMC / École polytechnique). Contact information: LM D, Palaiseau. Philippe Drobinski > philippe.drobinski@lmd.polytechnique.fr GAME , Toulouse. Véronique Ducrocq > veronique.ducrocq@meteo.fr 01 Téthys II, CNRS - INS U’s coastal oceanographic research vessel, is also taking part in the measuring campaign. 02 View of a glider, an underwater measuring device. 03 The instrumented Falcon 20 (CNRS - INS U / Météo-France / CNES ), ready to take off to probe the atmosphere. 04 Interior of the ATR 42 aircraft, loaded with instruments to analyze airborne particles. 02 03 01 04 © A. Lieu vin/CNRS © J. PUSCEDDU/CNRS Pho tothèqeu © A. Lieu vin/CNRS © T. CARIOU/SBR/CNRS Pho tothèque ONLINE. Follow the HyMex campaign's daily operations: > www.ipsl.fr/Actualites/Evenements/Carnet-de-campagne-HyMeX


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