X band polarimetric and Doppler radar observations of precipitation variability over the mediterranean region (France)
Résumé
The Mediterranean region is known to be characterized by a high spatial and temporal variability of precipitations. Precipitations fluctuations in time and space are due to a large spectrum of processes from climate dynamics to droplet formation. Because of its latitude (between 36° and 44° N) the Mediterranean region is affected by sub-tropical storm as well as mid-latitude synoptic disturbances. Hence the summer is warm and dry while being persistently affected by the Azores anticyclone and the winter is temperate and moderately humid because of the mid-latitude westerlies. Moreover since the Mediterranean is surrounded by mountain barriers, and strong contrasts between sea and continent exist, local forcing is also important. Our work aims at examining the environmental conditions and precipitation structures of storms observed in these regions and at improving our knowledge about the life-cycle of the more intense events and processes that govern their evolution. It uses observations gathered by the X band polarimetric & Doppler weather Radar HYDRIX. This radar, owned by the LATMOS/CNRS, developed and operated by NOVIMET, collects in an operational way since 2008 reflectivity, Doppler and polarimetric data with a time step and a spatial resolution of 5 minutes and 1 km respectively. In addition to these data, derived products such as instantaneous rainfall, cumulated rain, cell displacement and hydrometeor classification are obtained in real time. It also provides Doppler information in clear air region. All these data can be used to document the low level environment and the internal dynamics, microphysics and the interaction-mechanisms (wind shear, ...) leading to high-accumulated surface rainfall. The presentation will be devoted to the temporal and spatial characterisation of the precipitation that affects the 100 km radius region around Nice in a range from annual to daily scale and to the analysis of the universal scaling behavior of the rain. To document those two topics, we analysed the data with the help of various tools such as rain frequency and mean, cumulative distribution function, fourier and wavelet transform.