Hailfall in southwest France: Relationship with precipitation, trends and wavelet analysis

- Hailfall characterization, relationship with total precipitation, southwest France
- Variables analyzed: precipitation; hail day number; hailfall frequency; and intensity
- Mann-Kendall test used to study trends and wavelet analysis to study periodicities.
- Wavelet coherence used to analyze the influence of NAO on the variables.

Precipitation in southwestern France was analyzed. Monthly rainfall data from the Global Precipitation Climatology Centre (GPCC) were used to obtain three clusters of average precipitation from May through September for the period 1901-2010. We attempt to understand the role of hailfalls in total precipitation using three different variables related to hail, the number of hail days, hail frequency, and intensity. We examine trends via the Mann-Kendall test and periodicities by wavelet analysis. The results show cluster classification of precipitation to be somewhat consistent with hailpad networks in the study area. In the Pyrenees, there was a non-significant negative trend of precipitation and a substantial increase of hail days and intensity of hail, which were close to the limit of significance. Finally, a wavelet coherence analysis shows a strong influence of the North Atlantic Oscillation (NAO) in the Atlantic region.