How to compute residual transport of volume in a bay

[Rafael_Santana]

Dear users,

I am running a seasonal ROMS simulation with tides and wind for the Todos os Santos bay, located northeastern Brazil. At the beginning, I started calculating the residual transport by multiplying the monthly (average of 29 tidal cycles) residual velocity and the area. The area is equal to distance between grid points times the depth added to the residual sea level, [dx*(dz+zeta residual)]. After one year, the residual transport is equal to -1984 m^3/s or 60x10^9 m^3 going out of the bay, which would dry the bay 5 times. I also have tried to compute the residual transport of volume using the hourly outputs, the results were different, but the magnitudes were still the same.

If you have an idea of what is happening, please let me know.

Kind regards,

Rafael

[kate]

Are you using residual u or ubar? If u, then the sum should be over u*dz*dx, with this dz being a residual too. The model dz terms contain the zeta contribution already. You might be better using ubar*(h+zeta)*dx if you don't have the residual dz.

[Rafael_Santana]

Thanks Kate,

Actually, at the beginning I used residual (or monthly averages) of vbar_northward (at rho points)*dx*(h+zeta residual). Then I summed the residual transport through the section, positive transport plus negative transport to obtain the residual transport.

I was wondering if the eulerian residual circulation do not represent well the residual transport of volume. Because I calculated the residual transport in five different sections (Fig 1 and 2) of the bay using averaged vbar and it showed contrasting values (Fig 3). However, when I interpolated the hourly outputs to six minutes I got better results (~2000 m3/s of inflow and outflow in both bay entrance) (Fig 4) (five minutes ago) . I am starting to believe that with more discretized outputs to calculate the transport (approaching an integral) I can achieve more reliable results. Although, there are some questions to answer, as: Why residual transport is constrasting at the same entrance?