inverse barometer effect on a costal lagoon

[flcastej]

Hi !!

I am trying to model the sea level fluctuations on a coastal lagoon,after getting good result forcing the model with winds, I want to simulate the inverse barometer effect.

I have use the preprocessor option ATM_PRESS with PJ_GRADP, but I don´t get any fluctuation on the sea level. As I understand, the option ATM_PRESS is usefull working with gradients of atmospheric pressure, but in my case I have the same value for the entire domain, could it be the problem?. The grid I am using get only the lagoon, the interconection channels between open sea and lagoon, and a little area of open sea, so should I :

1:) Change the code and force ZETA to change with the atmospheric pressure, variation of 1mb -> 1 cm (zeta).

2.) Impose the sea level variation as a boundary condition.

3.) Use a bigger grid that allow to represent the fluctuations on the sea level.

4.) Use two nesting model.

5.) Use an option of ROMs that I don´t know ( I am a begginer on ROMs)

6.) Other suggestion or comments.

Thanks a lot !!

[wilkin]

If you have the same atmospheric pressure everywhere, its gradient is zero and it has no impact on the dynamics.

[flcastej]

So, if I want to model the inverse barometer effect, should I use a grid big enough to have an atmospheric pressure gradient? Use a bigger grid will have a higher computational time cost, so I should use a nesting model, isn´t it?

Thanks a lot for your answer.

[m.hadfield]

I should think that in a coastal lagoon, the only way atmospheric pressure variations will affect the interior is by causing the sea level at the lagoon entrance(s) to vary, causing water to surge in and out. So what you need is a time series of sea level at the entrance(s), bearing in mind that if there is more than one entrance, differences between them will be important.

So you need either good measurements or a model to create some virtual measurements. If you're using a model, you probably need it to cover quite a large area of continental shelf, and to include the effects of surface pressure and wind-generate surface stress, remembering that trapped waves will propagate along the shelf & coast from areas of remote forcing. (John Wilkin knows much more about this than I do.) To me that indicates a lagoon model nested (1-way, off-line nesting should do) inside a shelf model.

Just my $0.02.

[flcastej]

Thank´s a lot for your help, finally I will try to use a lagoon model nested (1-way, off-line nesting should do) inside a shelf model (2D) to model correctly the sea level fluctuations.

Happy new year !!!