Quality Analysis of the 2016 Quantitative Precipitation Estimates in the French Alps

The French Alps region has a specific character, with very various sub-regions from the Mediterranean Sea shore to the top of Europe, including several mountain massifs with summits close to or above 4000 m. In this region, the quality of radar Quantitative Precipitation Estimation (QPE) can be locally limited due to radar beam blockages, the distance to the radars, and the altitude. In recent years, Météo-France has made important investments to improve this quality. In December 2015, the French national QPE mosaic (1-km/5min resolution) started assimilating several new local radar QPEs, estimated from the Swiss instantaneous rainfall rate mosaic (Faure et al. 2015) and from measurements of 3 X-band radars installed by Météo-France at altitudes 1740m, 1770m, and 1910m (Kabeche et al. 2011), and recently qualified for operational use. An other local QPE estimated from measurements of an Alpine X-band radar operated by a private company is also assimilated since March 2017.

This presentation highlights the results of a study realised at the beginning of 2017, to evaluate the impact of these new data assimilations, and to characterise the current radar QPE mosaic quality in the French Alps, in order to identify the needs for new improvements which could necessitate future investments.
Daily measurements of around 450 rain gauges, and hourly measurements for more than 220 of them, have been compared to corresponding radar QPE for the entire year 2016. The results have been analysed at the scale of the entire mountain chain, as at the scale of each mountain massif or large valley of major interest (high population, industry, tourism, natural hazards vulnerability). The analysis results describe the improvement of the QPE quality from 2015 to 2016 thanks to the new local QPEs assimilated, show and explain the spatial variability of the current radar QPE quality in the French Alps, and allow to define the parts of the territory where this quality is still too weak and where complementary solutions would be required.

References:
Faure Dominique, Gaussiat Nicolas, Tabary Pierre, Urban Bernard, Real time integration of foreign radar quantitative precipitation estimations (QPEs) in the French National QPE mosaic, 37th Conference on radar meteorology, AMS, September 14-18, 2015, Norman, OK, USA.

Fadela Kabeche, Jordi Figueras i Ventura, Béatrice Fradon, Abdel-Amin Boumahmoud, Pascale Dupuy, Samuel Westrelin, and Pierre Tabary, Quantitative precipitation estimation (QPE) in the French Alps with a dense network of polarimetric X-band radars, 35th Conference on Radar Meteorology, AMS, September 25-30, 2011, Pittsburgh, PA, USA.