Icelandic climate and North Atlantic cyclones in ERA-40 reanalyses

Abstract

The frequency of winter cyclones in the North Atlantic is determined for 1957-2002 in the ERA-40 European Center for Medium-Range Weather Forecasts (ECMWF) reanalysis data set. The cyclone frequency shows distinct maxima for the intensity and the variability between southeastern Greenland and Iceland. The numbers of cyclones near Iceland (50 - 60N, 30 - 10W) and their intensity show an increase consistent with the North Atlantic Oscillation (NAO) and decreasing surface pressure in Iceland during 1961-2001 (station Reykjavík). Noteworthy is the decrease in near surface temperature (previously found) and 10m wind speed. Positive correlations are observed for the numbers of Icelandic cyclones with the NAO-index, the Icelandic surface pressure, and wind speed, while near surface temperature is not correlated. For precipitation the correlation with the cyclones is higher than with the NAO-index.