THE IMPACT OF A SEVERE WEATHER EVENT ON TRACE GAS DISTRIBUTIONS IN THE TROPOSPHERE AND THE STRATOSPHERE

We present an analysis of satellite-based trace gas measurements from the Global Ozone Monitoring Experiment (GOME) on board the European Remote Sensing Satellite (ERS-2). The data was recorded during the severe weather event in November 2001 over the western Mediterranean and Northern Africa. 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 North Africa and later on the Balearic Islands. Associated with the meridional transport an intrusion of stratospheric air below three km above sea level was observed. Very high values of the potential vorticity 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 (NO2) above the western Mediterranean. We could 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.