Impacts of the solar eclipse of 11 August 1999 on routinely recorded meteorological and air quality data in south-west Germany

The total solar eclipse of 11 August 1999 over Central Europe was also visible in Baden-Wuerttemberg, a state in south-west Germany. To investigate the impact of the total solar eclipse on the lower planetary boundary layer, meteorological and air quality data extracted from routine measurements at six sites in Baden-Wuerttemberg were examined. The meteorological data were recorded at the Plittersdorf meteorological station (in the path of totality of the total solar eclipse) and at the Forestmeteorological Site Hartheim (outside the path of totality of the total solar eclipse). The air quality data were obtained from four official air quality monitoring stations located at Freudenstadt, Karlsruhe-West, Rastatt and Welzheimer Wald, all of which lie within the path of totality of the total solar eclipse. Due to cloudiness, weather conditions on 11 August 1999 were not optimal in south-west Germany. However, the transient reduction (followed by a rise) induced by the total solar eclipse on meteorological variables including global solar radiation, upward longwave radiation, net radiation, air temperature, horizontal wind speed, elevation angle of the three-dimensional wind vector as well as turbulent sensible and latent heat fluxes was quite obvious. Despite unfavourable weather conditions, half-hourly mean values of ozone routinely measured at the above-mentioned standard official air quality monitoring stations showed a varying decline up to 27% at the urban station Rastatt and 37% at the background station Welzheimer Wald. This decline was owing mainly to the fall in global radiation during the total solar eclipse. However, additional influences by advection and deposition can not be precluded.