The Meteorological Research Flight (MRF) was a Met Office facility, which flew a well-instrumented C-130 Hercules aircraft for atmospheric research purposes.

This dataset contains airborne atmospheric and chemistry measurements taken on board the Met Office C-130 Hercules aircraft flight A752 for the Atmospheric Chemistry and Transport of Ozone in the upper troposphere-lower stratosphere (UTLS) (ACTO) campaign. The flight was located over the Irish sea.

The purpose of the flight was to investigate various filaments of air in the upper troposphere. These were to include uplifted, polluted air from Europe; dry ozone-rich air of stratospheric / upper tropospheric origins and high relative humidity air from the marine boundary layer.

The different filaments did appear to be found but further post-flight analysis will be required to confirm the origins. Polluted air was noted with higher NOx mixing ratios. A filament of dry ozone-rich air was also found but at a more southerly position than forecast: it was not investigated in detail but flown through on an approximately Northward leg (i.e. an across-filament run). High relative humidity air was observed at the northern end of the flight track, as forecast. This air had ozone mixing ratios, which were lower than those observed on any of the earlier flights (down to a minimum of around 35 ppb), quite consistent with air of clean marine origins.

One interesting feature that was observed, between the high-ozone/low relative humidity air and the low ozone/high relative humidity air, was an area of high relative humidity and relatively high ozone (around 65 ppb). This was clearly correlated with a small but notable increase in peroxide and a good peroxy radical signal: i.e. a region indicating notable ozone loss. This was not one of the regions forecast to be of particular interest but nevertheless it may be very interesting.