Problem about tracer boundary condition

[Yomi]

I want to simulate the diffusion of initial dye concentration in the research domain, and I tested four kinds of tracer boundary conditions in the west boundary,

Test 1: WEST_TGRADIENT
Test 2: WEST_TRADIATION + WEST_TNUDGING， OBCFAC=2
Test 3: WEST_TRADIATION + WEST_TNUDGING， OBCFAC=100
Test 4: WEST_TCLAMPED

In the Test 2~4, I added much lower dye data in the west boundary than the initial dye concentration. So the simulated dye concentration after several days was supposed to decrease due to the addition of the low dye data in the west boundary

However, to my surprise, the dye concentration in the research domain after simulating 42 days in Test 1~3 were almost the same and still very high, and that in Test 4 was much lower, which means the boundary dye data that I added did not work in Test 2 & 3. I wonder why this happened, should I modify other parameters beside OBCFAC when I use WEST_TRADIATION + WEST_TNUDGING?

Thanks in advance!

[kate]

That combo boundary condition depends on the direction of the currents on the boundary. Is it flowing in from the west? If so, it should be bringing in your low values. If not, check the relevant bits of code to see. Are they being applied to all tracers or just the first NAT of them? I would look, but I'm running a newer code in which the boundary conditions are being set through the LBC variable in ocean.in - each tracer gets its own line.