THE 1991 WMO INTERNATIONAL OZONESONDE INTERCOMPARISON AT VANSCOY, CANADA

An intercomparison of ozonesondes was held at Vanscoy, Saskatchewan, from 13 to 24 May 1991. The intercomparison, which was sponsored by the WMO and hosted by the Atmospheric Environment Service (AES) of Canada, was attended by scientists from six countries: Canada, Finland, Germany, India, Japan and the United States. Four different makes of ozonesondes were used: the ECC sonde, the Brewer-Mast sonde, the Indian ozonesonde and the Japanese RSII-KC79 ozonesonde. These represent most of the sonde types that are in routine operation in the Global Ozone Observing System. A balloon payload and telemetry system was developed to accommodate up to eight ozonesondes that could operate independently and transmit data simultaneously to a ground receiver. Ten flights were launched, each carrying 7 or 8 sondes, and a total of 65 successful profile measurements were made. The payloads were carried to altitudes between 35 and 40 km. The measured profiles are used to determine statistically meaningful evaluations of the different sonde types. The results compared with those from previous intercomparisons indicate that there has been a general improvement in performance for most of the types. In addition there appears to have been changes with time in the relative sensitivity to tropospheric ozone for different sonde types. This result should be considered when drawing conclusions regarding trends in tropospheric ozone.