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CFC paper


Here are some comments on the latest draft of the CFC paper.  First, I want to
commend you for pushing the analysis and documentation of the CFC simulations 
forward.  I realize it is a huge task to try to make sense of the output of 13
models.  Furthermore, it is difficult trying to satisfy the large number of
coathors.  If it were not for you, however, we certainly would not be nearly
this far along with the paper.

Overall, I think the paper is in good shape, but there are a number
of areas that need to be attended to before it can be submitted.  I've listed
all of my comments below, but I realize that time may not permit you from
addressing them all.  In other words, I think your plan of a July submission
is a good one.  Also, by the way, I think JGR would be an ideal journal to
submit to.

(1) There are a number of grammatical and spelling errors that need to be
corrected.  I carefully went through the paper and made hand-written changes
directly on the manuscript, which I will FEDEX to you today.

(2) I think the goal of the paper needs to be stated more clearly.  I suggest
inserting the following after the second sentence of the last paragraph of
the introduction

The paper has two main goals.  First, we wish to characterize the abilities of
the models to ventilate the ocean on the time scales relevant for anthropogenic
CO2 uptake.  This characterization is necessary for assessing the accuracy of
the predictions of anthropogenic CO2 uptake by the OCMIP-2 models.  The second
goal of the paper is to present to the ocean and climate modeling communities
an evaluation of the decadal scale ventilation characteristics of the major
state-of-the-art ocean general circulation models (OGCMs) used in long-term
climate modeling today.  Our evaluation is largely qualitative in that we
cannot pin down the exact causes for differences among the models and between
the models and observations.  However, we expect that our results will motivate
individual modeling groups to develop new parameterizations and conduct
sensitivity studies that will ultimately improve coarse-resolution OGCMs.

(3) I realize that a thorough description of all of the physical models is not
possible, but I think that there should be a reference for each model in the
project.  These references could be added as a row to Table 2.  I realize that
many modeling groups are using a version of their model that is not identical
to what has been described in the literature, but the closest reference should
be listed, perhaps even with a few words in the table about how the OCMIP model
is different from the published version.  Citing the physical model paper in
prep may also be a good idea (either Lindsay et al. or Doney et al., I would

(4) I like the idea of Table 3 and wonder if it should get a little more
discussion.  It might also be useful to break it down a little more regionally,
like tropics, subtropics and subpolar areas, and by basin.  You might add
inventory as well as flux, and possibly normalize to temperature.  It could get
a little long I suppose, but such a table would nicely complement the
inventory/penetration depth figures, where it is sometimes hard to distinguish
a particular model from the rest.

(5) Your statements in the third paragraph of the discussion section about
the relationship of the longitudinal uptake pattern to the surface buoyancy
flux are not substantiated.  You may be right about this, but you need to at
least cite some papers that show this relationship if you want to make this
statement.  Or else you could ask Keith to send you some of the surface flux
maps that he showed in Princeton and see how the CFC flux lines up with the
buoyancy flux.

(6) The conclusions need a bit of work.  I find that the paper ends a little
awkwardly, though I am not sure exactly how to reword things here.

(7) Figure 13 is very hard to read.  What would be ideal is to have the Orsi
figure put on the same color scale.  Is it possible to contact the author and
have him prepare such a figure, possibly in exchange for co-authorship?

Hope these comments are of some help.


Raymond G. Najjar
Department of Meteorology            Phone: 814-863-1586
522 Walker Building                  Fax: 814-865-3663
The Pennsylvania State University    Email: najjar@essc.psu.edu 
University Park, PA 16802-5013       home page: http://www.essc.psu.edu/~najjar