<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">I wonder if you considered the Coriolis term exactly as in the code, which involves averaging the four neighboring U points around the grid point where P_y falls. To be balanced, the forcing would have to be averaged in the same way. <br class=""><div class="">
<div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 20px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;"><br class="">Paola<br class=""></div>
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<br class=""><div><blockquote type="cite" class=""><div class="">On Feb 4, 2019, at 1:30 AM, Martin Losch <<a href="mailto:Martin.Losch@awi.de" class="">Martin.Losch@awi.de</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">Hi Bertrand,<br class=""><br class="">I am not sure if I understand what you want to do: You intialize u with a jet, which you want to make steady, but you add a body force that will change v (dv/dt = …). What is the balance, that you are looking for? <br class=""><br class="">Naively, I would think, it is the geostrophic balance. But in geostrophic balance dv/dt and du/dt = 0 and you have rho*f*u = -dp/dy and and rho*f*v = + dp/dx. If the jet is along x, then v = 0, so dp/dx = 0, and you just have to make sure that in your intial conditions dp0/dy = -rho*f*u0. For a barotropic case that would mean d\eta/dy = f*u0/g in your intial conditions. <br class=""><br class="">Without any extra forcing this jet would decay due to friction in the system (and some v will appear). Depending on your question, you could restore u to the inital conditions (you can use the rbcs package for that), but that will always damp the system<br class=""><br class="">Martin<br class=""><br class="">On 2. Feb 2019, at 23:38, Bertrand Louis Rene Delorme <<a href="mailto:bdelorme@stanford.edu" class="">bdelorme@stanford.edu</a>> wrote:<br class=""><blockquote type="cite" class=""><br class="">Hi everyone,<br class=""><br class="">I am trying to set up a configuration with just a steady, deep, zonal jet in the water column balanced by the Coriolis force. To do that, I prescribed the jet as initial condition (u0) and I added a body force (BF) in the v-momentum equation such that dv/dt = -f*u + BF with BF=f*u0. I used apply_forcing.F to incorporate the body force by adding the following lines in APPLY_FORCING_V:<br class=""><br class="">DO j=1,sNy+1<br class=""> DO i=0,sNx+1<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>yv = 0.5*(yC(i,j,bi,bj)+yC(i,j-1,bi,bj))<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>gV_arr(i,j) = gV_arr(i,j) + 1E-7 * exp(-(rC(k)-mZ)**2/sigZ**2) * exp(-(yv-mY)**2/sigY**2)<br class=""> ENDDO<br class="">ENDDO<br class=""><br class="">where (mY, mZ) are the coordinates of the center of the jet in the meridional plane, sigZ and sigY the e-folding scale in each direction, and yv is the y-coordinate on the V-grid. Concerning the initial condition for U, I was careful to define it on the U-grid. <br class=""><br class="">However, for some reasons, the jet is not perfectly balanced and low amplitude waves emanate from its center. I feel like I might be doing something inconsistent in apply_forcing.F, like not using the appropriate grid, but couldn't figure out what it is. If anyone has an idea on what might go wrong please let me know.<br class=""><br class="">Thank you,<br class=""><br class="">Bertrand <br class=""><br class=""><br class=""><br class="">_______________________________________________<br class="">MITgcm-support mailing list<br class=""><a href="mailto:MITgcm-support@mitgcm.org" class="">MITgcm-support@mitgcm.org</a><br class="">http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support<br class=""></blockquote><br class="">_______________________________________________<br class="">MITgcm-support mailing list<br class=""><a href="mailto:MITgcm-support@mitgcm.org" class="">MITgcm-support@mitgcm.org</a><br class="">http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support<br class=""></div></div></blockquote></div><br class=""></body></html>