Análisis de los extremos pluviométricos en las Islas Canarias y su relación con el índice NAO

Abstract

This work studies the trends of extreme precipitation events in winter, spring and autumn for the period 1970-2010 in the Canary Islands. The existence of trends in extremes indices has been analysed applying the Mann-kendall statistic. Taking into account that mean precipitation generally shows a decrease in most of the islands, the study of trends found in the pxcdd and pxcwd indices in the west of the region, along with those found in the intensity indices (px3d, px5d and pint), shows a tendency towards a concentration of precipitation events in less days, resulting in the existence of more severe episodes. Furthermore, the behaviour of the analyzed indices (except for pxcdd) is very similar during winter and autumn but it differs in spring. On the other hand, we have addressed the possible influence of the North Atlantic Oscillation (NAO) in heavy rainfall episodes recorded in the Canary Islands. Results show that in the western half of the region, the relationship between days with heavy precipitation and negative NAO is clear, while for the eastern, there is a higher frequency of these events with positive NAO. For the relationship between rainy days exceeding the 95th percentile and extreme positive NAO (NAO ≥ +1) and extreme negative NAO (NAO ≤ -1), we can see few differences between eastern and western half of the Islands. However, most of these very rainy days are present for neutral NAO situations.