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<p dir="auto">DeltaT needs to be set to satisfy <a href="https://en.wikipedia.org/wiki/Courant%E2%80%93Friedrichs%E2%80%93Lewy_condition">the CFL condition</a>, ie. dt < dx/c where c is the speed of the fastest signals in your model, typically the mode-1 phase speed if surface waves aren’t being used. So, the # of grid cells only matters insofar as if your domain size doesn’t change, dx will increase/decrease, but it is dx that is the fundamental parameter. </p>
<p dir="auto">In the typical ocean c<4 m/s, so 60s should be good down to something like 500-m lateral resolution.</p>
<p dir="auto">You also need to be cognizant of dz values, particularly in cells with hFac<<1. Thats why there is a hFacMin parameter - if you set this to something ridiculously small you can get w > dz/dt.</p>
<p dir="auto">Its possible that a model run started from rest will have a strong initial adjustment period where you need a small deltaT, but then can increase it substantially after a few inertial periods (by restarting from a pickup file).</p>
<p dir="auto">Cheers, Jody</p>
<p dir="auto">On 14 Aug 2017, at 10:35, rahele shafiee wrote:</p>
<p dir="auto"></p></div>
<div style="white-space:normal"><blockquote style="border-left:2px solid #5855D5; color:#5855D5; margin:0 0 5px; padding-left:5px"><p dir="auto">Hello everyone<br>
<br>
I'm running a modell with grid points 510*450*32 for 1 year. I've chosen DeltaT=60, but the runtime is too long.<br>
<br>
I selected a experimental test with grid points 10*12*2 and DeltaT=60 and I run for 1 year and lasted 11 minutes, but with DeltaT=108000 it took a second to run. The same test with DeltaT=108000 for 5 years lasted 21 minutes and with DeltaT=5*108000=540000 lasted a second.<br>
<br>
How can I reduce the runtime of the model by modifying DeltaT? Is it possible to change DeltaT unstable the model after some time?<br>
<br>
Thanks for your guidance<br>
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