VINT

[Arlindo da Silva]

On Thu, Feb 28, 2008 at 6:33 PM, Remi Meynadier <
remi.meynadier at aero.jussieu.fr> wrote:

> Hi folks
> I am using the vint fonction to integrate specific humidity to obtain
> precipitable water.
>
> This is what I ve done : vint(ps,q,100) with ps surface pressure.
>

Just a small comment. Computing total precipitable water or any other mass
weighted vertical integral from constant pressure data is a rather
innacurate proposition.  Very often the interpolation from model native
vertical coordinates to pressure levels is not conservative, and the
mismatch between the surface pressure and lowest pressure level (usually
1000hPa) introduces non-negligible errors. (The largest contributions to the
integral come from the lowest layers.)

For this reason, most models provide separate 2D diagnostics with the
vertical integrals computed from native model coordinates. If you have a
choice, stick with these, or else use profiles in native vertical
coordinates. If pressure level data is all you have, keep in mind that it
only provides a rough estimate of the vertical integral.

  Arlindo

--
Arlindo da Silva
dasilva at alum.mit.edu
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://gradsusr.org/pipermail/gradsusr/attachments/20080303/db04ac3f/attachment.html