Résumé
The isotopic composition of precipitation is widely used to provide insights into hydrologic cycle, ecological processes and paleoclimate and to evaluate atmospheric models processes. However, in tropical regions, the need of a robust isotopic calibration is needed for further investigations. For this purpose, simultaneous measurements of the isotopic composition of both precipitation and water vapor is crucial. In this framework, we present here for the first time a 1-year long continuous water vapor isotopic record obtained in Niamey (Niger) (2010-2011) using the new laser spectroscopy technology. We will discuss this data-set, which is unique in the Tropics, with an emphasis over three timescales: (1) the diurnal cycle and its seasonal evolution, focusing on new information dealing with convective onset, organization, intensity and propagation and the role of cold wake during the monsoon season; (2) the intra-seasonal variability and the link with well-known African climate modes and (3) the seasonal scale dominated by both convective activity during the monsoon period and large scale subsidence during the dry season. We will also show that AGCM (LMDZ-iso) has important biases in simulating both diurnal, intra-seasonal and seasonal isotopic composition of water vapor, strongly suggesting a misrepresentation of convective parametrization and/or large-scale processes.