Match Campaign Manual

This manual is mainly but not only addressed to the staff of ozonesonde stations, which participate in ozonesonde Match campaigns. It gives some background and advice for the day to day business of a Match campaign. After touching briefly the aims of the Match campaigns a description of the Match method is given. Important advice about the submission of data and about the contact persons is given afterwards. The history of the Match technique as well as results are mentioned briefly. An attempt to acknowledge the work of the station staff is tried at the end.

For those not familiar with the stratospheric ozone problem The Ozone Hole Tour of the University of Cambridge is recommended.

The two main aims of Match campaigns are:

1. to measure the chemical ozone loss in polar regions, and
2. to check our understanding of the underlying processes.

The idea of Match is to probe, i.e. to determine the ozone content of, a lot of air parcels twice during their way through the atmosphere. This is achieved by coordinating the soundings roughly in the following way.

1. The trajectories (transport paths) of air masses, which had been measured by ozonesondes previously, are analysed and forecasted by meteorologists at the FU Berlin.
2. These trajectories are checked for cases when such an air mass reaches the vicinity of one of the participating measuring sites (ozonesonde station) within 10 days.
3. The staff at the ozonesonde station gets informed and is asked to launch an ozonesonde in order to examine the same air mass for a second time.

A decrease in the ozone concentration within the time period of the two sonde flights can then be attributed to chemical ozone depletion. Due to the great number of sonde pairs, statistically significant ozone loss rates can be determined.

The coordination scheme is shown in detail in the Figure below. The coordination team at AWI Potsdam sends out an alert message at least 24 hours (time period B) before a launch at a particular station is predicted to produce a match. The next day until 10:00 UT these stations usually will either get a confirmation message or a non-confirmation message for the requested sounding on the same day (time period A), depending on the newest forecast data. The confirmation message contains an updated optimal launch time and a launch window.

Sondes that can be released inside the launch window but not close to the optimal launch time should make the match also, but probably with a worse match radius. (The match radius is defined as the distance between the locations of the air mass in mind and the ozonesonde at the altitude of the air mass. Shorter match radii are more valuable for the analysis, of course.) The launch window is covering the whole period where a launched sonde is expected to make a match. Sondes launched outside the window can not be expected to make that match.

Any alert messages or confirmation messages which are send out are recommendations, only! Sometimes in rare cases it will happen, that trouble in receiving the met-data for computing the trajectories will delay the emission of these messages. In these cases the coordination team will be quite busy in getting the needed data and will usually not be able to give special advice to the station staff. However, the coordination team will of course try to serve every received request. In cases when time goes on and the station staff has to make a decision about an ozonesonde launch with respect to an alert message the day before, a launch due to the informations in the alert messages is recommended if the expected match radius is less than 250 km. In all other cases no ozonesonde launch is recommended like a non-confirmation message would do.

Alert and confirmation messages are send out according to the availability windows at the particular stations. Such availability windows vary quite a lot from station to station and look in the coordination files like e.g.:

During the Arctic campaigns mainly the stations north of 60 degree north are involved. However, usually once or twice during a winter polar stratospheric air moves across mid-latitudes. During these events the participation of all mid-latitude stations is highly welcomed and needed. In these cases the mid-latitude stations will get a separate, non-specific alert mail several days before.

Please provide all ozonesonde data as soon as possible. The prefered way is to upload the data to the Nadir data base at NILU. The corresponding directory is:

/nadir/projects/vintersol/data/o3sondes/STATIONNAME

The format should be the well known NASA Ames format 2160. If possible the nasaconv software developed at the Finnish Meteorological Institute (FMI) in Sodankylä should be used.

In case an ozonesonde data file cannot be transmitted to the Nadir data base within a reasonable time, the coordination team would be happy if the station staff would be able to follow one of two options:

An ozonesonde data file does exist: Please email the file to the coordination team with the phrase "Match data" in the subject line.
An ozonesonde data file does not exist, yet: Please email or fax a short message with standardised informations about the messured ozone profile to the coordination team. In case of a email submission please use the phrase "Match notice" in the subject line. The Match notice should have the following format:

Please find the details of the description in the glossary, when needed. It would be very helpful if this format would be strictly used, in order to serve automatic processes which subsequently follow in the coordination procedure.

Please report any changes in station characteristics immediately to the coordination team, i.e.

Changes in the availability window at the station in particular with respect to the last Match campaign. Changes in the communication coordinates (email address, fax number).

The campaigns will be coordinated by Holger Deckelmann with some assistance by Markus Rex and Peter von der Gathen at AWI Potsdam.

The quality control team at the FMI will have a look at the incoming ozonesonde data in near real time in order to search for typical profile features which cover most probable sonde failures and will flag them accordingly.

The Nadir data base at NILU, where all ozonesonde data should be uploaded, will be supervised by Aasmund Fahre Vik.

Email addresses of the contact points above will be send out by separate emails to the particular stations in order to avoid spam emails.

During the north-hemispheric winter 1991/92 an concerted campaign funded by the EU and national agencies, the European Arctic Stratospheric Ozone Experiment (EASOE), took place. The activities included the launch of a large number (~1400) of ozonesondes in the Arctic and in the mid-latitudes. This data set were used afterwards to determine Arctic ozone losses for the first time with the Match method. Since the launches were not coordinated only matches were used which happened by chance. Fortunately, because of the large number of soundings enough matches had been found for a successful analysis. This way the method were established and for the Second European Stratospheric Arctic and Mid-latitude Experiment (SESAME) in the winter 1994/95 the method had been advanced to the active form with coordinated launches as described above. Since then in nearly each Arctic winter a Match campaign was performed. The only exceptions were the winters 2001/02 and 2003/04, which were relatively warm stratospheric winters with minor ozone losses. In the mean time the winters 1992/93 and 1993/94 were analysed by the passive Match approach, too. In total an analysed ozonesonde Match data exist for 12 Arctic winters and one Antarctic winter (2003).

The technique has been picked up by Sasano and co-workers for determining ozone loss rates from data of the space-borne sensor Improved Limb Atmospheric Spectrometer (ILAS) [Sasano et al., 2000; Terao et al., 2002].

The results of the Match analyses in the polar vortex have been published in several peer reviewed papers. A number of further papers which use Match results for detailed model studies or picked up the technique for own investigations have also been published. Most important outcomes and implications of the Match method are:

• It has been demonstrated that Match is able to distinguish between dynamical and chemical variations, i.e. Match is able to determine chemical ozone losses. The vertical and time resolution is one of the best reported.
• In the winter 1995/96 Match found a layer of air where nearly Antarctic conditions occurred, i.e. heavy denitrification prolonged the ozone loss long into spring.
• Match found the effect of the 'chlorine nitrate trap', cf. Rex et al. [1997].
• Match data is very well suited to be compared with model outputs in particular with box model outputs. Two successful studies revealed, that current photochemical models are not able to reproduce the observed ozone loss rates quantitatively [Becker et al. 1998; Kilbane-Dawe et al., 2001]. It has also been shown that the use of tracer data from a 3D model can improve the Match approach at higher altitudes.
• Match found a direct relationship between the minimum temperature an air parcel encountered during an resonable time period before the first sonde measurement and the ozone loss. This allowed to find treshold temperatures needed for ozone loss.

Acknowledgements

Ozonesonde station net (Arctic Match campaigns)