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 A751 for the Atmospheric Chemistry and Transport of Ozone in the upper troposphere-lower stratosphere (UTLS) (ACTO) campaign. The flight was a transit from Boscombe to Prestwick.

The main purpose was to investigate a filament of air (with UTLS origins), which had been apparent on the PV forecasts from ECMWF (interpretation by John Methven). The flight was very successful. In particular, the filament of air was located with relative ease. The filament was initially traversed during the ascent to the first level run. The filament position was then confirmed from the water vapour image, details of which were sent to the aircraft via satcom. A rectangular flight plan was carried out at FL230, with legs approximately along the axis of the filament, across the filament and along the outside of the filament. A triangular pattern was flown at the subsequent level, with the final leg running at a slight angle across the filament, such that the edge of the filament was crossed slowly.

The filament was apparent in many of the measurements: low humidity, low CN, high ozone (up to around 100ppb), higher PCASP aerosol and high NOy. Other features were apparent near the filament region including air parcels having some evidence of more recent pollution (higher NO and NO2). Hence, further investigation will be required to understand the origins of these parcels. A number of flask samples (37) were also collected for subsequent analysis,

There were a few instrument errors prior to flight. The CO and the HCHO were both unserviceable and the FWVS was not fitted. It is hoped that some of the other parameters may be used as tropospheric tracers instead of CO (aerosols, Leeds GC hydrocarbons, bottle sample-hydrocarbons (including methane), bottle sample GC-MS analysis and possible bottle sample CO).

Meteorology

The meteorological situation was dominated by a large ridge of high pressure, stretching from the Azores to Scandinavia. A weak warm front was analysed on the midday Met. Office Chart, oriented from SW to NE, stretching from 50N, 15W to Scandinavia. There was little cloud associated with the front: mainly a line of stratocumulus with some embedded cumulus (the largest having tops at 25,000ft). The main features appeared to be marked by a gradient in humidity, which was apparent on the water vapour satellite image. "