Re: rho_un output

[Ansley Manke <ansley@xxxxxxxxxxxxx>]

Hello Retish (and others on the thread),
Thank you for pointing out the error on rho_un in the Ferret Users
Guide.
It's been corrected in the latest version of the on-line manual.  
I'd  like to
take the opportunity to point everyone to the newest Users Guide, Version
5.22,
which we're making every effort to keep up to date.

http://ferret.wrc.noaa.gov/Ferret/Documentation/Users_Guide/v52/fer_html.htm

Ansley Manke
 

--Ansley Manke  Pacific Marine Environmental Laboratory  Seattle WA  (206)526-6246
 
 

Mr Retish Senan wrote:

Hi Karen!

        The correct usage of the rho_un function is
                        rho_un(sal,temp,Z[G=temp]).

So, the strange values you are getting is due to the fact that the
function is interpreting your temperature as salinity and vice versa..

        The confusion must have arised because the user's guide V4.91 has
given the wrong usage in an example on page 40. The correct usage is as
given in the list of functions on page 42.

Regards
Retish

On Wed, 18 Oct 2000, Karen Bice wrote:

> I have a netcdf file that contains temperature and salinity on an XYZ
> grid. I am trying to use the rho_un function to calculate density.
>
> When I say
> let density = rho_un(temp, sal, Z[G=temp])
> I get density values that can't be right.
>
> For example, for a specific X,Y location, values look like this (the
> first column is depth in cm):
>                 TEMP    SAL   DENS
> 1250     /  1:  27.61  36.76  1019.
> 3750     /  2:  27.62  36.78  1029.
> 6250     /  3:  27.64  36.80  1039.
> 11250    /  4:  27.64  36.82  1057.
> 18750    /  5:  27.58  36.84  1081.
> 41250    /  6:  24.83  36.10  1139.
> 68750    /  7:  20.58  35.46  1192.
> 111250   /  8:  16.30  35.11  1261.
> 151250   /  9:  14.24  34.97  1323.
> 188750   / 10:  13.30  34.90  1384.
> 238750   / 11:  12.60  34.85  1481.
> 301250   / 12:  12.17  34.83  1648.
>
> But, more reasonable UNESCO values for in situ densities (in kg/m^3) for
> these T,S values would be:
>  1250     /  1:  1023.93
>  3750     /  2:  1024.04
>  6250     /  3:  1024.15
>  11250    /  4:  1024.38
>  18750    /  5:  1024.73
>  41250    /  6:  1025.99
>  68750    /  7:  1027.92
>  111250   /  8:  1030.60
>  151250   /  9:  1032.71
>  188750   / 10:  1034.48
>  238750   / 11:  1036.73
>  301250   / 12:  1039.44
>
> I know that rho_un expects Z in decibars (according to the user's
> guide), so I figured that it was using the actual depth values. But even
> if that were the case, those depths, interpreted as pressures in
> decibars shouldn't yield densities like those in my first list above.
>
> Is the output of rho_un actually something other than kg/m^3?
> Can anyone tell me what I am doing wrong here and how I can get good
> density values out of rho_un?
>
> Thanks very much.
>
> --
> Karen L. Bice, Assistant Scientist            Mail Stop #23
> Dept. of Geology and Geophysics                       phone: (508) 289-3320
> Woods Hole Oceanographic Institution          FAX:   (508) 457-2187
> Woods Hole, MA                USA 02543-1541
>

<>*<>*<>*<>*<>*<>*<>*<>*<>*<>*<>*<>*<>*<>*<>*<>*<>*<>*<>*<>*<>*<>*<>*<>*<>
RETISH SENAN
Research Student
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