A lightweight balloon-borne gas chromatograph for in situ measurements of atmospheric halocarbons

A new lightweight gas chromatograph using a Carboxen microtrap to pre-conce ntrate the sample has been developed for in situ measurements of stratosphe ric chlorofluorocarbons (CFCs) from balloon platforms. The instrument has b een developed for fast analysis of a single tracer CFC-11 (CCl3F) to maximi ze the vertical resolution of ascent/descent profiles. In principle a wide range of halocarbons can be measured by changing operational parameters. Th e instrument weights < 25 kg and can easily be deployed on either the ballo on flight train or on gondolas. It has a time resolution of <2 min which co rresponds to a vertical resolution of 500-700 m for a typical balloon ascen t and better for a controlled slow descent. The precision of the CFC-11 mea surement is estimated to be 1.7% and the accuracy is currently estimated to be 2.9% with much of the uncertainty arising from the links to the absolut e calibration scale. An improved calibration procedure is being developed w hich should reduce this uncertainty. Test flights were completed in 1998 an d the instrument recently participated in the Third European Stratospheric Experiment on Ozone when a number of scientific flights were made. (C) 2000 American Institute of Physics. [S0034-6748(00)01512-4].