Re: [ferret_users] Ferret's definition of the earth radius

To: Olivier Marti <olivier.marti@xxxxxxxxxxxx>

Subject: Re: [ferret_users] Ferret's definition of the earth radius

From: Andrew Wittenberg - NOAA Federal <andrew.wittenberg@xxxxxxxx>

Date: Mon, 29 Feb 2016 13:14:57 -0500

Cc: Andy Jacobson - NOAA Affiliate <andy.jacobson@xxxxxxxx>, Ferret Users <ferret_users@xxxxxxxx>

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Andy, Olivier,

Note that Ferret's "area model" is a true sphere -- not a faceted "disco ball" like some old GCMs may have used (and Ferret had used, prior to version 5.90). Not sure if this is related to your regridding issue.

Andrew

On Mon, Feb 29, 2016 at 11:59 AM, Olivier Marti <olivier.marti@xxxxxxxxxxxx> wrote:

> Le 29 févr. 2016 à 16:18, Andy Jacobson - NOAA Affiliate <andy.jacobson@xxxxxxxx> a écrit :
>
> Hi,
>
> I'm trying to track down a problem conserving tracer mass in the GEOS-Chem model, using an emissions module called HEMCO. It has been suggested that differences may be due to conflicting definitions of the radius of the earth. As it turns out, I used Ferret to do my regridding, so I'm trying to discover what value Ferret is using. I found one definition in FERRET/fmt/cmn/gt_lib.parm (6371.e5 cm). Is there anywhere else that a value for the radius of the earth is defined in the ferret source code?
>
> Thanks,
>
> Andy
>
> --
> Andy Jacobson
> andy.jacobson@xxxxxxxx
>
> NOAA Earth System Research Lab
> Global Monitoring Division
> 325 Broadway R/GMD1
> Boulder, Colorado 80305
>
> 303/578-2237

Andy,

you can also ask to Ferret !

i.e :

!
! What is the Earth radius in Ferret

DEFINE SYMBOL MyPrec $1"360"

DEFINE AXIS/X=0:360/NPOINTS=($MyPrec)/EDGES/UNITS=degrees_east xax
DEFINE AXIS/Y=-90:90/NPOINTS=($MyPrec)/EDGES/UNITS=degrees_north yax

LET aire = 1.0 + 0*(X[GX=xax]+Y[GY=yax])
LET/UNITS="m^2" aire_sum = `aire[X=@DIN,Y=@DIN]`
LET pi = `ACOS (-1.0)`
LET/UNITS="m" ra = `(aire_sum/ 4.0 / pi)^0.5`

LIST/NOHEAD/QUIET/FORMAT=("Earth Radius in Ferret :", 1F20.6, " m") ra

Earth Radius in Ferret : 6370499.317638 m

--
Dr. Olivier Marti - mailto:olivier.marti@xxxxxxxxxxxx
Laboratoire des Sciences du Climat et de l'Environnement
Institut Pierre Simon Laplace
Laboratoire CEA-CNRS-UVSQ - UMR 8212
Tel : +33 1 69 08 77 27 - Mob : +33 6 45 36 43 74
Fax : +33 1 69 08 30 73
<http://www.lsce.ipsl.fr/Pisp/olivier.marti>