Karl Taylor wrote:
> John, et al.,
>
> I agree with Jonathan that the metadata in files should not include
> detailed model documentation, but should instead point to that
> documentation. That is what can be done with the CF global
> "references" attribute. Examples of the kind of information that
> would be usefully included in the the actual model documentation can
> be found at:
> http://www-pcmdi.llnl.gov/ipcc/model_documentation/ipcc_model_documentation.php
>
I agree that this is an excellent use of the references attribute.
What im after, though, is the ability for software to read netcdf files
and "do the right thing", in this case serve the data out, eg in a WCS
server. For that, I do need to know the Earth shape. It seems reasonable
to decide where to add these modest amounts of information into the file
itself, if the data provider wants to.
>
> With respect to the shape of the Earth in global models, it is
> invariably taken to be spherical. This approximation works well (and
> allows g, the acceleration due to gravity, to be taken as a constant)
> because to good accuracy "effective gravity" (i.e., Newtonian gravity
> + centrifugal "force" due to the Earth's rotation) is very nearly
> perpendicular to the Earth's surface. (The Earth has effectively
> deformed from sphericity so that this is true.)
>
> Larry Gates has recently examined again this approximation in J.
> Atmos. Science, 61, 2478-2487, 2004. Here is part of his abstract:
>
> With the exception of two terms in the meridional and vertical
> equations of motion that are unique to the spheroidal system, all of
> the metric and rotational terms in the spheroidal system correspond to
> those found in the familiar spherical formulation, but now have
> coefficients that are functions of both the spheroidal latitude and
> elevation. The unique spheroidal terms arise from the resolution of
> the difference between the directions of apparent gravity and
> Newtonian gravitation, which is neglected in the spherical formulation.
thanks very much, this is very useful to know.
Received on Wed Apr 06 2005 - 12:55:12 BST
