Lagrangian floats

General scientific issues regarding ROMS

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onken
Posts: 13
Joined: Thu Feb 15, 2007 12:19 pm
Location: Helmholtz Zentrum Geesthacht

Lagrangian floats

#1 Unread post by onken »

I have inserted 67 Lagrangian floats in a ROMS model in shallow water
(max water depth around 40 m). I expected the floats to move along
(potential) density surfaces in order to conserve isopycnal potential
vorticity, but several floats penetrate the density surfaces.
Here are my questions:
(1) The vertical position of the density surfaces has been computed from the
variable "rho" in the ROMS output. Is "rho" in-situ density or
potential density?
(2) How is the vertical displacement of the floats
computed? Along density surfaces or s-surfaces? Or don't the floats
know anything about density or vertical coordinates?

Thanks,
Reiner

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kate
Posts: 4088
Joined: Wed Jul 02, 2003 5:29 pm
Location: CFOS/UAF, USA

Re: Lagrangian floats

#2 Unread post by kate »

rho is in situ density which is what we need for horizontal pressure gradients.

From a floats.in file:
T Float trajectory type (1: Lagrangian, 2: isobaric, 3: Geopotential)
The Lagrangian ones move with the local velocity. The others behave differently.

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