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New to the group are; Jim Sussler who is a PDRA working with Rod Jones, Kate Searle who is a Ph.D. student of John Pyle, Samantha Pullen a Ph.D. student of Rod Jones and Owen Garrett. Owen takes over Uplot, Uedit and local support from John Stringer. John left us in September to work for UNIRAS in Denmark. If you need to contact John, his new email address is johns@avs.uniras.dk. I gather that John is jet-setting away the world most of the time doing demos of the UNIRAS software and is currently porting the new version of the package onto the Cray. We wish John and his girlfriend Jan all the best for the future.
Owen proved his worth when I was away in New Zealand by managing to keep the local network up and running with just a day's crash course in system management! All questions and bug reports about Uplot or Uedit should be mailed Owen who's Email address is: owen@atm.ch.cam.ac.uk.
Glenn Carver
Satellites make measurements of atmospheric constituents by a range of methods, and at a range of times and locations. They do not make measurements on a regular spatial grid. This makes analysis of satellites measurements rather complex.
The analysis of chemical trace species has received little attention in comparison with the analysis of meteorological variables. Current methods tend to treat species independently, ignoring the complex balances which exist between species. Moreover, the large diurnal variations in the concentrations of many species are either accounted for in very simple ways, or avoided by analysing concentrations at fixed local time.
For the first time the very powerful technique of four-dimensional variational data assimilation has recently been applied to the analysis of chemically active trace species (Fisher & Lary 1994). The technique can combine observations with a numerical model to analyse simultaneously any observations of species made over a time window of a few days, i.e. no crude time or spatial averages are made. The analysis method is able to exploit information which is not available to conventional analysis techniques, such as the shape and amplitude of the diurnal cycles in species concentrations. Moreover, effective use can be made of asynoptic observations even for species which have strong diurnal cycles. Synoptic analyses are produced. This process could be repeated to build up a climatology of atmospheric trace gases.
Reference: Fisher, M., Lary, D.J., Lagrangian Four Dimensional Variational Data Assimilation of Chemical Species, Submitted to The Quarterly Journal of The Royal Meteorological Society, 1994.
Mike Fisher and David Lary
We have examined the temperature dependence of ClO near the stratopause where atmospheric dynamical effects are relatively small. The photochemical lifetime is of the order of a few seconds, and ClO is expected to be in photochemical equilibrium. Thus, near the stratopause (1-2 hPa), the ClO concentration is expected to be controlled by temperature and not on any dynamical effects.
In this study we have used the extended UGAMP model (the EUGCM) to predict the ClO concentration near the stratopause (1.5 hPa) for the northern hemisphere winter of 1991/92. We also compared the model results with ClO data measured by the microwave limb sounder (MLS). We found very good agreement between the model results and the MLS observations. Both the EUGCM results and the MLS data show a very strong temperature dependence of the order of 1000K. The temperature dependencies obtained from the MLS data and the EUGCM corroborate well with results from a photochemical box model.
Satyajit Ghosh, John Pyle and Peter Good
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