Baroclinic simulation with sigma layersBaroclinic simulation with sigma layershttps://oss.deltares.nl/c/message_boards/find_thread?p_l_id=1806765&threadId=11351522021-01-26T06:41:52Z2021-01-26T06:41:52ZRE: Baroclinic simulation with sigma layersFernando Barretohttps://oss.deltares.nl/c/message_boards/find_message?p_l_id=1806765&messageId=11433732017-02-13T15:01:22Z2017-02-13T15:01:22ZThanks for your reply Qinghua ,<br /><br />After some tests I realized that, for the sigma case, bottom slope is the key when stabilizing the model (for my specific case). After I removed the bottom slope, velocity magnitudes got much more "tamed", ranging around the input velocity (what is a very good thing). In this case, the stability seems to be controlled by vertical layers configuration. I'm still working on this but I think that few layers, as well as many layers, are both bad for the model stability (there is an ''inbetween''). After finding the best configuration for the number of layers and bottom slope I will play with the physical and numerical parameters.<br />In relation to initial conditions I will check my input and output data, and also smoothing time (I hope might help with this). Thanks, even a small perturbation can spoil the simulation, so we need to pay attention in every detail<br /><br />Regarding Z baroclinic case, I found out that the best results were achieved when refining both the surface and the bottom.<br /><br />For whom may concern, I will update any information in this thread so It can help others in the future <br /><br /><br />Regards, <br /><br /><br />Fernando TĂșlio Camilo BarretoFernando Barreto2017-02-13T15:01:22ZRE: Baroclinic simulation with sigma layersQinghua Yehttps://oss.deltares.nl/c/message_boards/find_message?p_l_id=1806765&messageId=11428492017-02-12T22:13:04Z2017-02-12T22:13:04ZHi Fernando,<br /><br />In general, Delft3D sigma layer have baroclinic mode simulation, which has been proved by several validation cases, such as lock exchange, salt intrusion in an estuary (3d sigma) etc. For your question, I guess it might be related to the improper combination of initial condition and boundary condition. Most probably it is because of the salinity/temperature data in the initial condition. <br /><br />One possible walk around might be using nesting. Not sure how difficult to get a good initial condition from a nested model. <br /><br />Hope this is helpful,<br /><br />Greetings,<br /><br />QinghuaQinghua Ye2017-02-12T22:13:04ZBaroclinic simulation with sigma layersFernando Barretohttps://oss.deltares.nl/c/message_boards/find_message?p_l_id=1806765&messageId=11351512017-02-02T23:36:19Z2017-02-02T23:36:19ZHi all, <br /><br />I am performing a 3D baroclinic simulation using 37 vertical sigma layers, in which the boundary and initial conditions were build from a<br />3D gaussian feature model representing the Brazil Current with a maximum core velocity of 0.2 m/s. Therefore, the boundary conditions are stationary.<br />The jet is in thermal-wind balanced. <br />The problem is, right after the simulation begins the velocity field gets completely destabilized, with peak velocities of 3 m/s, mainly <br />along continental slope. <br />Therefore my question is: is there any optimum set up for boundary and initial conditions and parameters when establishing a 3D baroclinic simulation with sigma layers?<br />I'm using Current boundary condition, with alpha=10000, nudge=#y#, and a sponge layers along boundaries. Attached is a figure with the initial condition for the surface velocity field, and the velocity field after 14 ts.<br />When simulating with uniform temperature and salinity (barotropic) the simulation runs much smoother. Time step is not the issue, I've run some tests.<br /><br />Thank you in advance a lot in advance.<br /><br />Fernando Tulio Camilo BarretoFernando Barreto2017-02-02T23:36:19Z