The primary objective of the European eXport of Precursors and Ozone by long-Range Transport (EXPORT) project is to characterise and quantify the photochemical air pollution both forming over Europe and being exported eastwards from Europe. The data held at BADC was collected during a co-ordinated 3 aircraft flying campaign in August 2000 based at Oberpfaffenhofen in Southern Germany. Measurements were made of many photochemical parameters including ozone, its precursors, other oxidants and both gas phase and particulate tracers in the air over Europe and that being transported eastwards out of Europe.

This dataset contains airborne atmospheric and chemistry measurements taken on board the Met Office C-130 Hercules aircraft flight A773 for the EXPORT project. The flight was over southern and eastern Germany.

Transport of Pollution through a Warm Conveyor Belt

From Oberpfaffenhofen the route was first to the far SW of Germany. However, in order to avoid the worst of the cloud (for the NOxy calibration) some retracing of our steps was required. Once at the south western waypoint, the plan was then to cross the front in a square wave pattern, travelling in a north eastern direction and increasing in altitude between runs. This was carried out successfully. We remained within the belt of cloud for much of the flight.

The flight appears to have been rather successful. Certainly transport of CO, HCHO, NOx and NOy (including PAN), out of the boundary layer, was very clear. The highest CO mixing ratios (ca. 150 ppb) were found at around 10:40 during a run at FL100. PAN at this time was estimated to be nearly 1 ppb. The following runs at FL120 and FL140 also showed elevated CO etc but CO maxima decreased with altitude. Whether all of the transport was due to the conveyor or if some of it was due to convection remains to be seen. The mixing ratio of ozone throughout the cloudy region was fairly constant (around 50 - 60 ppb); indicating that there had been limited photochemical processing.

Once clear of the northern edge of the cloud, the aircrew carried out a 50ft approach to an airfield in Leipzig. This allowed sampling of the boundary layer in the region and was quite a contrast to the rest of the flight. High SO2 readings (ca. 2 ppb) and high NOx readings (TECO NOx ca. 18 ppb) were observed but it should be noted that these were not concurrent: the maximum in NOx following that in SO2 by ca. 5 mins. During this time period the CN was off scale (the CO peaked at around 200 ppb and ozone was reduced to around 30ppb). The high concentrations of primary pollutants were unsurprising given the observation of large industrial chimneys etc in the area.

There were a fair number of instrument problems. The lower jNO2 and jO1D radiometers were found to go to full-scale for short periods. The HORACE TAS and TAT were clearly erroneous for a period of around half-an-hour starting at around 9:45 GMT. The flow in the PSAP instrument could not be maintained and missing 'O' rings needed replacing at the beginning of the flight. The FWVS was also found to drop down to -70.5°C fairly regularly. Early problems with the CO instrument (blown fuse) were soon rectified. All other chemistry equipment appeared to work well, despite the very wet conditions.

The Met Office midday analysis showed the surface cold front stretching from Northern France to the triple point at the Baltic Sea. The path across Germany was fairly closely matched by the flight plan.