Intensités des pluies en zones à relief : Premiers résultats sur un transect alpin de forte densité

Abstract

For regional estimations of floods, both rough models and station-data transfers are used. They all need local rain estimations. On relief basins, and even with only smooth hills, the rain statistical distributions present high micro-climatic variations, resulting from ''air-relief'' interactions. Generally, the rain-recorder network cannot be dense enough to allow a sufficient accurate mapping. Rain-radar seems to be a promising tool, but not yet operating. Using a set of favourable conditions (three parallel chains, increasing altitude, main rainy wind parallel, radar sustain...) , a permanent laboratory was created East of Lyon, in an ''ERB'' (European Reference Basin) spirit. Its economic feasibility was obtained by one-dimension (transect) structure, where a very high and sufficient density is possible, and surrounded by an ordinary regional rain-gauge network of medium density level. The atmosphere characteristics are obtained with the ordinary radio-sondages, eventually completed with interpolated data from meteorological forecasting models. The minimal time-path is one minute. The analysis of the first observations show, even for short time-paths, a very high level of a real structure, thus a probable possibility of a conceptual modelizing.