Atmospheric Chemistry and Transport of Ozone in the upper troposphere-lower stratosphere (UTLS) (ACTO) campaign. This dataset contains model output potential vorticity and C-130 flight track plots.

The Atmospheric Chemistry and Transport of Ozone (ACTO) in the UTLS was a round 2 UTLS (Upper Troposphere and Lower Stratosphere) project led by Stuart Penkett, University of East Anglia. This dataset collection contains airborne atmospheric chemistry data collected by the Met Research Flight (MRF) C-130 Hercules aircraft and atmospheric chemistry output. Data were already collected on the composition and structure of the troposphere as part of OCTA, ACSOE, and TACIA programmes, UTLS-DCFZ and EU-MAXOX during campaigns in the first half of 1999. There was an obvious progression from the objectives of the previous experiments and those of this project. Therefore analysis of the data from these programmes were valuable for the planning of the new measurement campaign, which were collected in the UTLS using the UKMO C-130 during 40 hours flying time, in the spring/summer period of the 2000. Flights were 3-6 hours and did take place in the North Atlantic off northern Britain and were predominantly in the upper troposphere (4 to 11km) with only occasional sorties into the lower stratosphere. Flights were designed to examine the chemical composition and reactivity of different air masses: boundary layer air (marine and (polluted) continental); tropical and subtropical air; upper tropospheric and lower stratospheric air; and polar air. Detailed meteorological and chemical forecast data were obtained from ECMWF, UKMO and NILU. Domain filling trajectory calculations, with forecast wind fields, were used to locate layers and to determine their orientation, whilst the NILU chemical forecast model provided information on the expected chemical composition of the different air masses. To determine the origin, composition and chemical activity of the different air masses found in the UTLS, measurements were made from a large number of tracers, ozone precursors, reactive species and photochemical products.

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 A750 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 reposition the aircraft at Prestwick for the ACTO detachment. The instruments were operated as an additional test. The data was also monitored for evidence of filaments of upper tropospheric / lower stratospheric air that had been forecast on the 3/5/2000. However, the forecast from 4/5/2000 had suggested that the air would have moved too far North. Thus as expected, there was no evidence of very dry, ozone-rich air, during the flight. There were several instrument errors prior to flight and these were not resolved during the flight. The peroxide instrument was not operated. The carbon monoxide was switched on but did not perform sufficiently to give any useful data. The PERCA operator was not happy with the performance of the instrument (low chain length). The PAN GC was operated on one channel only. The ozone instrument worked OK but it was not displayed correctly on HORACE. The instrument operator therefore made investigations towards the end of the flight in order to understand the problem. The remaining chemistry instrumentation (UEA NOxy, MRF NOx box and the UEA formaldehyde, Leeds hydrocarbon GC) all worked well. Meteorology The meteorological situation was dominated by a high pressure system that was centred to the North West of Scotland. A weak warm front was shown on the midnight analysis over the south of England: no rain was forecast on the PGM. Areas of stratocumulus and altocumulus cloud marked the front. No other notable cloud features were found during the flight.

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.

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 A753 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 further the various filaments of air that were sampled in flight A752. That is polluted air, having origins in the Mediterranean region; clean marine boundary layer air; ozone-rich, dry upper tropospheric air (from upper tropospheric jet) and also polluted boundary layer air, which has been uplifted from N. America. The region should be very structured having many different characteristics. The filaments of air were expected to be aligned zonally, sloping downwards to the North. The flight was successful in that some of the filaments were found. However, the filaments were not found in the expected area. During a level hold at FL160 (for air traffic) and at the beginning of the first run at FL170 (NOxy calibrations), a dry ozone-rich filament was sampled. Later during the same run, air with moderately high ozone (around 70 ppb), high relative humidity and elevated peroxide was observed. At the subsequent level (FL240) ozone mixing ratios were generally lower (around 45-50 ppb) and the CN count was elevated (2500). However, during the turn at ca. 12:10 on FL240 (SE corner of the flight), another dry, ozone-rich filament was found. A further filament was expected to the North but this was not found. Towards the end of the flight further investigations were made at FL170, in order to try to find the first area of high ozone air (i.e. the air that was sampled during the first NOxy cal run). This air was found but interestingly, the ozone-rich dry air also correlated with high PAN and black carbon. The instruments generally worked well. The FWVS was adjusted in flight and then found to maintain a good correlation with the GE. Neither the CO nor the HCHO were flown due to previously existing faults. There was a problem with the peroxide pump but this was not until the end of the flight. Meteorology The meteorological situation was dominated by high pressure, centred to the north of Scotland. The south of the country was in a more showery regime. However, not much cloud was observed during flight: small cumulus, broken stratocumulus and some cirrus, were observed at times.

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 A749 for the Atmospheric Chemistry and Transport of Ozone in the upper troposphere-lower stratosphere (UTLS) (ACTO) campaign.

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. "

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 A756 for the Atmospheric Chemistry and Transport of Ozone in the upper troposphere-lower stratosphere (UTLS) (ACTO) campaign. The flight was located over the North Atlantic. "Stratospheric Studies, with a low tropopause The tropopause was crossed in this experiment in order to study true stratospheric air with the available instrumentation. Ozone mixing ratios of up to 400ppb were measured and the corresponding CO mixing ratios were around 30 ppb. The discrimination between the two NOy channels was quite apparent: indicating a clear presence of HNO3. PAN was just detectable in this air. On descending back below the tropopause, at around 22,000ft, it was noted that the NOy channel, with the Rosemount inlet, was suddenly found to measure more NOy than the other NOy channel. This correlated better with a change in humidity than with the change in temperature. It has been suggested that the change in conditions causes nitrogen compounds (HNO3?) to be 'flushed off' the inlet. Suggestions have been made to change the inlet to the make it identical to the other inlet (backward facing PFA). The instruments generally worked well. There were some problems with the peroxide, as the flows were very poor, at FL270 and above, and the formaldehyde was measuring high values, thought to be due to a leak in the inlet line. The carbon monoxide instrument showed good anti-correlation with the ozone, after the first run at FL250 (when there were problems due to blockages affecting the flow to the optical filter). It was observed that the HORACE reading is high by about 15 ppb relative to the PC reading. Meteorology The situation was dominated by a low pressure system centred over Ireland (centre pressure 1000mb). The associated low tropopause made the situation ideal for studying stratospheric chemistry with the C-130.

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 A757 for the Atmospheric Chemistry and Transport of Ozone in the upper troposphere-lower stratosphere (UTLS) (ACTO) campaign. The flight was located over the North Atlantic.

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 A754 for the Atmospheric Chemistry and Transport of Ozone in the upper troposphere-lower stratosphere (UTLS) (ACTO) campaign. The flight was located over the North Atlantic. The objective of this flight was to investigate the chemistry and physics of uplifted air, contrasting air masses in the upper troposphere and lower stratosphere. The flight was just under six hours in duration. Most instrumentation ran well throughout the flight, in particular the carbon monoxide instrument was operational for the first time during the campaign. Three hours and 30 minutes into the flight a PFC fire extinguisher was discharged in the rear van. After investigation, by the load master and the flight leader, a decision was made not to evacuate the van or initiate a smoke and fumes incident. There is some concern that bottle samples taken during the flight may be contaminated. The mission scientists were pleased with the flight: we intercepted a northerly conveyor belt with uplifted Mediterranean air. We were able to do runs parallel with the filaments both to the north and south of the gradient. Throughout the flight the clouds and haze were exactly as expected from the satellite pictures and met. forecasts.