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An automated contrail detection algorithm has been applied to AVHRR data to obtain the position of contrails. Nearly simultaneous data from the Europe Model of the Deutscher Wetterdienst have been used to find typical weather conditions associated with 742 persistent contrails. Further, a flow pattern analysis identifies typical regions where the occurrence of contrails was above average. These regions are in the upper atmosphere: (a) ahead of a surface warm front either in moist warm layers before the cirrus clouds arrive or more likely with the cirrus in a warm conveyor belt and (b) ahead of a surface cold front in rapidly moving cold air in the turbulent regions near a band of strong wind (though the speed is not necessarily as high as in a jet). Usually, the atmosphere is baroclinic in the contrail region. Most of the detected contrails occur in divergent flow patterns in the upper troposphere in slowly rising warm or locally turbulent cold air masses. Copyright © 1999 Royal Meteorological Society

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An iridescent aerodynamic contrail (AerC) of a 2-engine aircraft f ying from Amsterdam to Copenhagen was observed and photographed at Norderney on 27 June 2008, 14:06 UTC. In order to see whether this event was caused by an unusual weather situation we investigate the meteorological situation. It turns out that the situation allows AerC to become visible because it was warm enough and suff ciently moist. The dynamical situation is studied, and it seems that the stable stratif cation at the f ight level of 350 hPa supports the appearance of an AerC. Additionally we investigate the ambient cloudiness where interesting halo features have been displayed in cirrus clouds. We examine the special colours of the Norderney aerodynamic contrail which allows to conclude that the width of the ice crystal size distribution is the factor directly relevant for iridescence, in this case representing a mixture from different growth histories. Finally we present an argumentation that AerC can be differentiated from jet contrails as soon as they display iridescence which requires an angular distance from the sun of less than about 30 • .

An analysis of the severe weather event in November 2001 over the western Mediterranean is presented focusing on satellite-based trace gas measurements from the Global Ozone Monitoring Experiment (GOME) on board the European Remote Sensing Satellite (ERS-2). This study is supplemented by a synoptic analysis and simulations of the three-dimensional stratospheric chemical transport model ROSE. Arctic air masses moved rapidly from Scandinavia to the Iberian peninsula and were mixed with subtropical air over the still warm Mediterranean Sea. This caused severe thunderstorms and extreme rainfall along the coasts of Morocco and Algeria and later on the Balearic Islands. Associated with the meridional transport an intrusion of stratospheric air below 3 km above sea level was observed. The maximum potential vorticity (PV) derived from UK Meteorological Office analysis data was about 9.3 potential vorticity units (pvu) at 330 K at the equatorward position of 35 • N. These very high values went along with remarkably enhanced total ozone levels obtained from GOME backscatter measurements of collocated GOME/ERS-2 overpasses. Further investigation of GOME data showed unusually high levels of nitrogen dioxide (NO 2 ) above the western Mediterranean. We present a new method to derive the tropospheric content of nitrogen dioxide (NO 2 ) from a combination of satellite measurements and results of a chemical transport model. We show that about two-third of the total atmospheric content of nitrogen dioxide in the observed plume is found in the troposphere, due to lightning activity, advection and vertical transport in the thunderstorms from the planetary boundary layer (PBL) to atmospheric levels above clouds.