Changes in the probability of extreme daily precipitation observed from 1951 to 2002 in the Iberian Peninsula

Abstract

ABSTRACT:In this study trends in the probability of extreme rainfall in the Iberian Peninsula at a daily scale from 1951 to 2002 have been analysed. A simple statistical model of daily precipitation based on the gamma distribution is applied to data from 22 stations in the Iberian Peninsula from 1951 to 2002. The Mann-Kendall test was applied to look for trends of the distribution parameters. It is shown that the scale parameter remains stable, while the shape parameter is most variable, spatially and temporally, with significant negative trends in many stations. As a consequence, the trend of the probability of daily rainfall lesser than the 5th percentile is positive, mainly to the north and to the south of the Iberian Peninsula; meanwhile the probability of daily rainfall higher than the 95th percentile is negative. This behaviour, with slight spatial differences, is observed in the four seasons of the year. Results corresponding to the probability of heavy rainfalls are confirmed using the stretched exponential distribution. The possible influence of teleconnection patterns (North Atlantic Oscillation, East Atlantic, Mediterranean Oscillation pattern) is analysed calculating the correlation coefficients between teleconnection indices and the gamma distribution parameters. The winter NAO index shows significant relationships with the scale parameter, but not with the shape parameter. The East Atlantic pattern shows significant correlation coefficients with the shape parameter of 5 stations in winter, and 5 stations in autumn, but these results are not conclusive. These results suggest that the decrease of this parameter, and the behaviour of extreme rainfall probabilities, must be explained by other mechanisms.

Change of extreme rainfall indexes at Ebro River Basin

“…However, they also observed that the number of days with moderate, intense and very intense rainfall was diminishing, especially in spring and winter. This same result was found by Rodrigo (2010), who adjusted daily precipitation at a gamma distribution from 1951 to 2002 and showed the evolution of the scale and shape parameters.…”

“…If the rainfall distribution has changed, it is necessary to determine whether there are specific sub-periods of time with a similar distribution. This type of treatment was not carried out in certain works that studied the evolution and probability of rainfall exceeding dangerous thresholds (Gallego et al, 2006;Rodrigo, 2010;Müller et al, 2009). These authors found a lack of stationarity in rainfall during the 1951-2002 period, especially in terms of extreme values.…”

Daily precipitation concentration across Europe 1971–2010

“…across the Mediterranean basin (Norrant and Douguedroit, 2006;Moberg et al, 2006;Gallego et al, 2006;Brunet et al, 2007;Rodrigo and Trigo, 2007;Durao et al, 2010;Toreti et al, 2010). Thus, Reiser and Kutiel (2010) concluded that no generalized temporal changes have been detected in the daily rainfall regime across the Mediterranean basin, but the results depend on density of observations, study period, and area analysed; therefore, several trends in the probability of various daily rainfall categories have been suggested (Rodrigo, 2010).…”

Spatio-temporal trend and statistical distribution of extreme precipitation events in Huaihe River Basin during 1960–2009

“…Researches on extreme precipitation event especially on the spatio-temporal and statistical distribution analysis have attracted more and more attention in the past several decades (Zhang and Wei, 2009;Alexander et al, 2006;Rodrigo, 2010;Trömel and Schönwiese, 2007;Unkašević et al, 2004). For example, Alexander et al (2006) investigated global observed changes of daily climate extreme of precipitation.…”