Re: [ferret_users] Vertical velocity in Soda3.15.2 monthly mean data

[Ryo Furue <furue@xxxxxxxxxx>]

Dear Satheesh,

On Thu, Aug 3, 2023 at 8:43 PM Satheesh Shenoi <shenoi1958@xxxxxxxxx> wrote:

This is my first post to this group.

I have "soda_3.15.2_mn_ocean_reg_*.nc" data obtained from https://www2.atmos.umd.edu/~ocean/index_files/soda3.15.2_mn_download_b.htm

It has T,S,U,V, dia-surface velocity T-points, SSH, etc. 

Please advise how I can estimate vertical velocity using the available information.

A short answer is, vertically integrate the continuity equation w_z = - u_x - v_y, where the horizontal derivatives are calculated with Ferret's differentiation operators.

But, I have no idea how robust the result will be.  Vertical velocity is a noisy quantity and an ad-hoc method like this may give you an unreliable answer.

To get a robust result,

1. First, examine the SODA manual to find out what grid configuration SODA uses.  For example, let's assume that it uses the C grid.

2. Use the C-grid continuity equation to calculate vertical velocity, which should be identical to the vertical velocity within SODA.   (SODA must have vertical velocity internally. Whether it saves/outputs it or not is a separate issue.)

I don't think you can do this within Ferret.

Ryo