Re: [ferret_users] Latitude, longitude to length conversion while calculating derivatives in Pyferret ?

To: ferret_users@xxxxxxxx

Subject: Re: [ferret_users] Latitude, longitude to length conversion while calculating derivatives in Pyferret ?

From: "Ansley C. Manke" <ansley.b.manke@xxxxxxxx>

Date: Fri, 26 Jul 2019 14:07:57 -0700

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Hi,

Ferret/PyFerret does units conversions and takes distances on the earth into account when the grid units are well defined. Please see this documentation: https://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/variables-xpressions/XPRESSIONS#GeneralInfo

It also discusses multi-directional transformations; including the cases where area-averaging is used

-Ansley

On 7/22/2019 11:46 PM, VL Srinivas wrote:

Hello,

While calculating derivatives say, dU/dx, it is written as U[X=@DDC] for central difference. But, the dimension X is in degrees(longitude) and velocity U in m/s.

Do I need to convert the degrees of X into metres during calculation? Or is it embedded in Pyferret to convert it into metres while calculating ?

Thank you.

--

Regards,
V.L.Srinivas.

--
Ansley Manke
NOAA/PMEL Science Data Integration Group
7600 Sand Point Way NE
206-526-6246