<div class="gmail_quote">On Thu, Feb 28, 2008 at 6:33 PM, Remi Meynadier <<a href="mailto:remi.meynadier@aero.jussieu.fr">remi.meynadier@aero.jussieu.fr</a>> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Hi folks<br>
I am using the vint fonction to integrate specific humidity to obtain<br>
precipitable water.<br>
<br>
This is what I ve done : vint(ps,q,100) with ps surface pressure.<br></blockquote><div><br class="webkit-block-placeholder"></div><div>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.)</div>
<div><br class="webkit-block-placeholder"></div><div>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. </div>
<div><br class="webkit-block-placeholder"></div><div> Arlindo</div><div><br class="webkit-block-placeholder"></div><div>-- <br></div></div>Arlindo da Silva<br><a href="mailto:dasilva@alum.mit.edu">dasilva@alum.mit.edu</a>