problem in plotting

[nageswararao]

Dear all,
I am implementing ROMS-2.2 for indian ocean region. After 5years run with climatology I had forced my model with quickscat winds. When I am ploting the surface temperature for my domain in ferret I am getting some squares in the vicinity of coast. Why these squares are coming into picture? Here is the link to see the image " http://www.incois.gov.in/Images/sst.gif " . Any help is appreciated.

Thanks in advance.

[kate]

If you get a checkerboard of alternating values, that is one way to contour it. It is called two delta-x noise. Can you plot a vertical slice through it? Are you doing any kind of horizontal smoothing on temperature? We often don't need to when using the third-order upwind advection scheme since it has some smoothing built in. One way to get this sort of noise is through noise in the vertical mxing scheme - which one are you using? Have you plotted its fields? For LMD, the boundary layer depth often has this sort of noise in it. Have you looked at the vertical velocity fields? They are often noisy like this too, especially at mid-depth.

[nageswararao]

Thanks Kate for ur reply.
I am not doing any horizontal smoothing of temperature. I had used LMD mixing only. I had used splines vertical advection scheme for u,v and 4th-order Akima vertical advection for temperature,salinity.
When I had plotted vertical slice in that region I am not getting proper thermocline i.e., there is no sudden decrease of temperature with depth between some 50 to 500m. I am getting temperature nearly about 20C at 500m depth. Not only here allover the domain I am getting.
Did u mean vertical velocity fields means w(vertical momentum component)? I am getting zero values upto some 2000m or so and then some +/- 0.5m/s to extreme depth.
Where I can get the mixing fields to plot? Can u please tell me.
So how can I overcome from this noise appearence in my surface temperature plot ?Please guide to get noise free plot of my variables.
Thanks in advance.

[kate]

The ascii input file ocean.in has switches for turning on and off the writing of a long list of variables. First of all, since you have LMD_MIXING, do you have LMD_SKPP? You probably want it. If so, you want to output and plot Hsbl, the depth of the surface boundary layer. Hsbl will affect the veritcal mixing coefficients Akv, Akt, Aks and is often noisy with 2 dx junk.

I believe the word on vertical splines advection is don't do it unless you have a lot of vertical resolution. You might try other advection options.

You can always apply a horizontal diffusivity explicitly. Make sure it is along level z surfaces or along isopycnals, not along the s-coordinates.

[nageswararao]

I switched on the SKPP only. When I plotted the mixing fields hsbl,akv,akt,aks, I got the same noise(squares) but not near the coast in different region. I had used the horizontal mixing along z-surfaces(geopontential) only. Why this noise is coming? how can I rectify it? please do reply.
Thanks in advance.

[yjtack1234]

Hello, nageswararao.
Do you resolve this problem?

Recently, I faced the same problem using Akima advection schemes.
I tried to change diffusion, viscosity coefficients for removing temperature noise but, I couldn't get good results.

If you resolve this problem, please give me some tips.

Thank you.