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Re: minor corrections, a plea for consistency


Does it make sense to include air pressure variation for some tracers and
not for others? Why not be consistent: decide what factors to consider, and
then consider those factors for all tracers. If I am going to put something
in my code to computer surface pressures using total atmospheric pressure,
why should I add a branch that says "don't do this for cfc's"?



P.S.  I know  this won't make any real difference, so don't let me block a

>I would agree that sea level atmospheric pressure need not be included in
>the CFC protocols, but for additional reasons.
>Your arguments seem appropriate for the vertical perspective for "natural"
>tracers.  Supplemental reasons can be given when considering horizontal
>variability. Horizontal temperature variation has a much larger effect on
>the gas transfer coefficient for CFC's than for CO2.  For CO2, the
>temperature variation in the gas transfer coefficient's solubility and
>Schmidt number terms almost cancel one another out; such is not so for
>CFC's.  Variability in CFC concentrations is much larger due to changes in
>temperature T than due to changes in atmospheric pressure P at sea level.
>For CFC's, modelers need to take into account temperature driven
>variability but can live with a 3% error due to changes in P.
>Furthermore, one must consider anthropogenic tracers.  In a 1-D vertical
>sense, the dynamic range for CFC's is much larger than for anthropogenic
>CO2 and post-nuclear C-14 simply because measurements can be made with
>much greater precision, not because of a relatively greater recent
>increase in the atmosphere.  So vertical reasoning won't work here;
>however, horizontal arguments given above still seem appropriate.
>-- Jim
>   James Orr                       Laboratoire des Sciences du Climat
>   LSCE, CEA Saclay                             et de l'Environnement
>   Bat. 709 - Orme                 Unite Mixte de Recherche CEA-CNRS
>   F-91191 Gif-sur-Yvette Cedex    Phone:   (33) (0)1 69 08 77 23
>   FRANCE                          Fax:     (33) (0)1 69 08 77 16
>                                             |    |
>   mailto:  orr@cea.fr            (country code)  (when in France)

Ken Caldeira
Climate System Modeling Group
Lawrence Livermore National Laboratory
7000 East Ave., L-103
Livermore CA 94550 USA

tel: (925)  423-4191 (new area code!)
fax: (925)  422-6388
e-mail:  kenc@LLNL.gov