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The North Atlantic Oscillation and Extreme Precipitation Indices Over Europe

The purpose of this study is to present results about the variability of some extreme precipitation indices in winter (DJF) over Europe and to find causes for the occurrence of extreme indices by considering the influence of the North Atlantic Oscillation (NAO) pattern. We will present results on the following climate indices: the ratio of precipitation greater than the 90th percentile to the total precipitation (R90ptot); wet days index (RR1) or the number of days where precipitation is at least 1mm; heavy precipitation days (R10mm) or the number of days with precipitation is at least 10 mm. We use the daily gridded dataset derived through interpolation of station data (E-OBS) version 2.0 (Hofstra et al. 2009). The variability of the indices would be analyzed by means of Empirical Orthogonal Function to reduce the dimensionality and regionalize the climate indices, we also use regression analysis to find association between the extreme indices and the NAO. Some discussions about the trend of the climate indices and results derived of the comparisons between extreme and mean precipitation will be shown. The motivations to perform this study are the greater vulnerability of ecosystems to climate extremes and the interest to derive statistical models to characterize how warmer climate would affect the occurrence of the climate extremes.

Hofstra, N; Haylock, M; New, M; Jones, PD (2009) Testing E-OBS European high-resolution gridded data set of daily precipitation and surface temperature. Journal of Geophysical Research- Atmospheres, 114, D21101, 21101-