# Re: precipitable water

From: Michael Notaro <mnotaro_at_nyahnyahspammersnyahnyah>
Date: Wed Feb 23 2011 - 09:55:56 MST

Slightly better...now it has the map outline.

What's wrong with the precipitable water calculation
because it looks awful?

xlat=a->xlat
xlon=a->xlon
q=a->qv ; kg per kg
ps=a->ps ; hPa
sigma=a->sigma
A=a->sigma
A=0.0
P0=0.0
dp_sigma = dpres_hybrid_ccm(ps,P0,A,sigma)
dp_sigma=dp_sigma*100.

dp_sigma!0 = ps!0
dp_sigma!1 = "plevel"
dp_sigma!2 = ps!1
dp_sigma!3 = ps!2

pw = prcwater_dp(q(time|:,iy|:,jx|:,kz|:),dp_sigma(time|:,iy|:,jx|:,plevel|:))
copy_VarCoords(ps,pw)

pw@long_name = "total column precipitable water"
pw@units = "kg/m2"
pw@coordinates = "xlat xlon"

out->pw=pw
out->xlat=xlat
out->xlon=xlon

On Feb 22, 2011, at 6:24 PM, Dennis Shea wrote:

> One approach
>
> [1]
> http://www.ncl.ucar.edu/Document/Functions/Built-in/dpres_hybrid_ccm.shtml
>
> This uses:
> p(k) = A(k)*PO + B(k)*PS
> The B(k) are the the sigma levels.
> A = sigma
> A = 0.0
> P0 = 0.0
> dp_sigma = dpres_hybrid_ccm(ps,P0,A,sigma)
> dp_sigma!0 = ps!0 ; (say) time
> dp_sigma!1 = "plevel"
> dp_sigma!2 = ps!1 ; lat
> dp_sigma!3 = ps!2 ; lon
> printVarSummary(dp_sigma)
>
>
> [2]
> http://www.ncl.ucar.edu/Document/Functions/Built-in/prcwater_dp.shtml
> pw =
> prcwater_dp(q(time|:,lat|:,lon|:,sigma|:),dp_sigma(time|:,lat|:,lon|:,plevel|:))
>
> pw@long_name = "total column precipitable water"
> pw@units = "kg/m2"
>
>
>
>
> On 02/22/2011 02:36 PM, Michael Notaro wrote:
>> How can I compute precipitable water
>> on a lat2d x lon2d grid using sigma
>> coordinates, given water vapor mixing
>> ratio output and surface pressure?
>>
>> Thanks, Michael
>> _______________________________________________
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>
>
> --
> ======================================================
> Dennis J. Shea tel: 303-497-1361 |
> P.O. Box 3000 fax: 303-497-1333 |
> Climate Analysis Section |
> Climate & Global Dynamics Div. |
> National Center for Atmospheric Research |
> Boulder, CO 80307 |
> USA email: shea 'at' ucar.edu |
> ======================================================
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Received on Wed Feb 23 09:56:08 2011

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