Raimundas Vidunas School of Mathematics and Statistics, University of Sydney Detecting persistent regimes in the North Atlantic Oscillation time series Wednesday 26th July 14:05-14:55pm, Carslaw Building Room 373. The North Atlantic Oscillation (NAO) is a dominant factor of atmospheric variability in the Northern hemishpere. It is characterized by the (anti)correlation of winter weather patterns in the Nothern Europe and subtropical Atlantic, noticed already by seafaring Scandinavians. The NAO indexes are calculated(by James Hurrell) from recorded sea level pressures for the last 140 years. In this talk, we consider the most variable winter seasonal NAO index, which is just a time series of length 142. Rather straightforwardly, we look at the distribution of the NAO values, thus disregarding their temporal order. It appears that this distribution differs drastically from the Gaussian normal distribution, with about 10 peaks. This suggests that some NAO index values appear persistently often, and that there must be persistent regimes of European winter weather patterns. We check whether the NAO value distribution varies with time, and check other climatic time series for occurence of persistent regimes.