Assessing the accuracy of weather radar to track intense rain cells

ERAD 2012 - THE SEVENTH EUROPEAN CONFERENCE ON RADAR IN METEOROLOGY AND HYDROLOGY
Assessing the accuracy of weather radar to track intense rain cells
and to analyse the relationships with topography and land cover in
the area of Greater Lyon area, France
Florent RENARD, Jacques COMBY
Université Jean Moulin Lyon 3 - CNRS UMR 5600 Environnement Ville Société – France
[email protected]
Presenter : Florent RENARD
The Greater Lyon is a dense area located in the Rhône Valley in the south east of France. The conurbation
counts 1.3 million inhabitants and the rainfall hazard is a great concern. However, until now, studies on
rainfall over the Greater Lyon have only been based on the network of rain gauges, despite the presence of
a C-band radar located in the close vicinity (Renard et Comby, 2007). Consequently, the first aim of this
study was to investigate the hydrological quality of this radar. This assessment, based on comparison of
radar estimations and rain-gauges values concludes that the radar data has overall a good quality since
2006. Given this good accuracy, this study made a next step and investigated the characteristics of intense
rain cells that are responsible of the majority of floods in the Greater Lyon area (Renard, 2009). Improved
knowledge on these rainfall cells is important to anticipate dangerous events and to improve the
monitoring of the sewage system (Renard et al., 2012). This poster discusses the analysis of the ten most
intense rainfall events in the 2001-2011 period. Spatial statistics pointed towards straight and linear
movements of intense rainfall cells, and the speed of these cells was found nearly constant during a
rainfall event, but depend from event to ranges on average from 25 to 66 km/h. These cell characteristics
seem, in a first overview, independent on the ground surface conditions and the topography underneath.
That’s why the second aim of this study is to sharply analyse the relations between the characteristics of
the rainfall cells and the topography and the land cover underneath. To study the relationships between
rainfall cells characteristics (intensity, orientation, speed, etc.) and topography, a 25m resolution DEM is
used. Concerning the land cover, the Corine Land Cover database is used. The results tend to confirm the
first hypotheses.
- RENARD F., 2010. Le risque pluvial en milieu urbain. De la caractérisation de l’aléa à l’évaluation de la
vulnérabilité : le cas du Grand Lyon. PhD thesis, University Jean Moulin Lyon 3, 528 p.
- RENARD F., CHAPON P.-M., COMBY J., 2012. Assessing the accuracy of weather radar to track
intense rain cells in the Greater Lyon area, France. Atmospheric Research, n°103, pp. 4-19
- RENARD F., COMBY J., 2007. Caractérisation de l’aléa pluviométrique en milieu urbain: le cas du
Grand Lyon. Climatologie, vol. 4, pp. 131-144