Ozone signatures of climate patterns over the Euro-Atlantic sector in the spring

The influence of low-frequency tropospheric dynamics upon column ozone interannual variability is estimated in the spring season over the Euro-Atlantic sector. This dynamical variability of tropospheric origin is examined in terms of leading climate patterns, derived from an empirical orthogonal function analysis of the National Center for Environmental Prediction 500 mb geopotential height analyses. In order to fingerprint the spatial and temporal ozone signatures of these patterns, the Total Ozone Mapping Spectrometer satellite observations of column ozone during the last two decades are used. The geographical ozone signatures of these climate patterns are extracted by linear regression and their time evolution reconstructed. Geopotential anomalies associated with four leading patterns of variability (the North Atlantic Oscillation (NAO), the Scandinavian pattern, the east Atlantic pattern and the European blocking pattern) induce column ozone anomalies in the range of 5-15 Dobson Units per standard deviation of the pattern index. The impact of these combined Euro-Atlantic climate patterns upon the regional ozone trends and interannual variability is also estimated. In order to reconstruct the regional ozone trend and variability, it proved important to incorporate several patterns, in addition to the dominant NAO. A hitherto little-known lifting of the Arctic tropopause by the polar night jet is also shown to imprint upon the ozone signatures of some patterns.