ISOTOPIC VARIABILITY IN SOME INTRA-STORMS IN THE REGION OF NIAMEY, NIGER

During the 1992 rainy season, in the sahelian region (Niger), some imp ortant convective systems were sampled at a scale smaller than the eve nt, to measure the variability of stable isotopes of water (oxygen-18 and deuterium). The evolution of the the isotopic content of rainfall shows a good agreement with the processes described by the physical me teorological model of the sahelian convective system. With the knowled ge of the main mechanisms governing the min system, isotopes point out the contribution of the the different sources of vapour during the st orm. (C) Academie des sciences/Elsevier, Paris.