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Special Feature
Radars Detecting Hazards Caused by Precipitation in Mountains

http://www.bulletins-electroniques.com/actualites/63932.htm

In the mountains, small catchment areas on steep, often barren terrain channel rainwater directly into torrents and rivers causing erosion, overflows and devastating floods. This is an alarming issue as local operators in charge of hazard prevention do not have the means to predict the sudden phenomena and assess their seriousness. Of course, Météo-France (French Weather Bureau) uses hydrometeorological radars operating on C or S bands with ranges of about 120 kilometers in low-lying regions to measure precipitation in real-time and predict dangerous situations, such as flash floods. However, the screen of high terrain prevents the radar network (called ARAMIS, Application Radar Infra-Synoptic Meteorology) from seeing the Alpine and Pyrenees mountain ranges. Ground-based rain-gauge networks cannot accurately measure precipitation because it varies substantially from one place to the next in the mountains.

So, in 2008, RHYTMME (Risques Hydrométéorologique en Territoires de Montagnes et Méditerranéens, hydrometeorological hazards in mountain and Mediterranean regions) was deployed. The CEMAGREF and Météo-France managed project developed under the 2007-2013 State-Region contract is co-funded by the European Union, the Ministry in charge of Ecology (General Directorate for Risk Prevention) and the Provence-Alpes-Côte d'Azur Region. RHYTMME relies on the deployment of a network of new generation radars operating on the X band, which are more compact, easier to install and less expensive. They provide precipitation measurements every five minutes with a resolution to the square kilometer, but with a shorter range of 30 to 60 kilometers. The radar characteristics make them ideally suited for mountain deployment. They are also capable of identifying the type of precipitation (e.g., rain, snow, hail) and measuring wind speed during rainstorms.

For the project, Météo-France teams have been briefed to exploit fully the innovative properties of the new radars. CEMAGREF scientists specialized in mountain and Mediterranean region hazards are working with CETE experts (specialized in landslides) on the dynamics of the hazards that precipitation may cause in catchment areas. The goal is to provide local authorities with a full-service platform of forecasting techniques of natural hazards and dangerous events to improve risk management in mountain regions. The Project also includes local partners specialized in natural hazards, who will be the users of the platform warning services (RTM, mountain terrain restoration agency and ONF, National Forestry Agency).

One X-band radar is operational on Mont Vial (Alpes-Maritimes département) as part of an earlier research project while the first RHYTMME funded radar will be installed on Mont Maurel (Alpes-de-Haute-Provence département) this autumn. By 2013, two other X-band radars will later installed in the Provence-Alpes-Côte-d'Azur Region. In the long-term, the project may be broadened to include other mountain regions in France or abroad, which are faced with the same natural hazards.

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- Cemagref - Patrice Mériaux - Phone: +33 (0)4 42 66 99 51 - email: patrice.meriaux@cemagref.fr
- Météo-France - Samuel Westrelin - Phone: +33 (4) 42 95 90 71 - email: samuel.westrelin@meteo.fr

Code brève
ADIT : 63932

ADIT - Jean-François Desessard - email: jfd@adit.fr

eTech France numéro 243 (5/07/2010) - ADIT / ADIT - http://www.bulletins-electroniques.com/actualites/63932.htm