boundary condition not absorb

[Dan_chan]

Hi,
I am having an issue with the temperature output from my ROMS model. The temperature seems to be bad at the open boundary, as shown in Figure 1. I have compared the ROMS output with the sst data from ERA5 and avhrr-oisst datasets. I also checked the boundary netcdf compared to the ROMS output and found that the boundary condition isn't being absorbed well.The temperature profile at the boundary is very different between the ROMS output and the boundary condition, as shown in Figure 2 for the month of September.
My Lateral Boundary Conditions (LBC) are set as follows:

Code: Select all

   LBC(isFsur) ==   Clo     Cha     Cha     Clo         ! free-surface
   LBC(isUbar) ==   Clo     Fla     Fla     Clo         ! 2D U-momentum
   LBC(isVbar) ==   Clo     Fla     Fla     Clo         ! 2D V-momentum
   LBC(isUvel) ==   Clo     RadNud  RadNud  Clo         ! 3D U-momentum
   LBC(isVvel) ==   Clo     RadNud  RadNud  Clo         ! 3D V-momentum
   LBC(isMtke) ==   Clo     Gra     Gra     Clo         ! mixing TKE

   LBC(isTvar) ==   Gra     RadNud  RadNud  Gra \       ! temperature
                    Gra     RadNud  RadNud  Gra         ! salinity

I I am not sure what is causing this issue and how to fix it. Can anyone help me with this?

Thank you very much in advance.

sst of ROMS output compared to obs

temperature profile of ROMS output and boundary

[Dan_chan]

Hi, I change my configure of TNU2, TNUDG and OBCFAC, and the boundary condition becomes better. Before, I use similiar configure of upwelling which set them as zero. But, it seems not suitable in my case. Hope to learn more of how to configure my roms.in later.

[chenzhixing]

Hi, I change my configure of TNU2, TNUDG and OBCFAC, and the boundary condition becomes better. Before, I use similiar configure of upwelling which set them as zero. But, it seems not suitable in my case. Hope to learn more of how to configure my roms.in later.

Hello, I have meet the same question for salinity in the boundary. In the roms.bry, salinty in east boundry is about the 31, while the salinty in the modeling of the east boundry is about 23 in the same time. So I suspected salinity of the boundary was not input into the model. How did you solve the problem?
In my roms.in, the Lateral Boundary Conditions (LBC) are the same as you chose, and the TNU2, TNUDG and OBCFAC are 0 m2/s, 240 days and 60.

[Dan_chan]

Hi, Chen
I think I may not explain clear before, I changed TNU2 from 0 to 10, which help diffusion of TS, It looked better. However, actually, I find I not solve the problem at all. There is still strong error at southern boundary, it appears only in May, June, July and Aug at surface. I am try to find another cause to this error.

[Dan_chan]

I apologize for my earlier premature enthusiasm. While the large-scale anomaly at the eastern boundary has indeed disappeared, a narrow anomaly remains at the southern boundary. Even after moving south boundary northward, contracting the simulation area, this anomaly persists. Moreover, it is particularly prominent in the surface layers during the months of May, June, July, and August. The anomaly in June, in particular, stands out the most. The figure illustrate the results of sea surface temperature and current fields for June, captured at both the surface and a depth of 50m. These results were obtained from the model simulations and Mercator reanalysis, respectively.

[Dan_chan]

I change my ''bry.nc'', the results become better, though the figure of two "bry.nc" seem nearly same. I will continue to check is there any invisible requirements when make boundary file.