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<div>from MITgcm/model/inc/PARAMS.h</div>
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<div>C deltaT :: Default timestep ( s )</div>
<div>C deltaTClock :: Timestep used as model "clock". This determines the</div>
<div>C IO frequencies and is used in tagging output. It can</div>
<div>C be totally different to the dynamical time. Typically</div>
<div>C it will be the deep-water timestep for accelerated runs.</div>
<div>C Frequency of checkpointing and dumping of the model state</div>
<div>C are referenced to this clock. ( s )</div>
<div>C deltaTMom :: Timestep for momemtum equations ( s )</div>
<div>C dTtracerLev :: Timestep for tracer equations ( s ), function of level k</div>
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<div>but I recommend that for your problem you just set deltaT so that you have:</div>
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<div>deltaTClock = deltaTMom = dTracelLev = deltaT</div>
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<div>D.</div>
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<blockquote type="cite">
<div>On Sep 3, 2024, at 6:05 PM, 唐鸿 <tanghong22@mails.ucas.ac.cn> wrote:</div>
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<p><span style="font-family:Times New Roman;font-size:13px;">Dear MITgcm Support Team,</span>
</p>
<p><span style="font-family:Times New Roman;"><br>
</span></p>
<p><span style="font-family:Times New Roman;font-size:13px;">I hope this message finds you well.</span><span style="font-family:Times New Roman;">
<span style="font-size:14px;"></span><br>
</span></p>
<p><span style="font-family:Times New Roman;"><br>
</span></p>
<p><span style="font-family:Times New Roman;"><span style="font-family:Times New Roman;font-size:13px;">I am currently working on a simulation project using the MITgcm to study the dynamics of a lake, including the freezing process during winter. I have encountered
some confusion regarding the behavior of the model with respect to the parameters
</span><strong><span style="font-family:Times New Roman;font-size:13px;">deltaTtracer</span></strong><span style="font-family:Times New Roman;font-size:13px;">,
</span><strong><span style="font-family:Times New Roman;font-size:13px;">deltaTmom</span></strong><span style="font-family:Times New Roman;font-size:13px;">, and
</span><strong><span style="font-family:Times New Roman;font-size:13px;">deltaT</span></strong><strong><span style="font-family:Times New Roman;font-size:13px;">Clock</span></strong><span style="font-family:Times New Roman;font-size:13px;">, and I am seeking
your guidance.</span></span> </p>
<p><span style="font-family:Times New Roman;"><br>
</span></p>
<p><span style="font-family:Times New Roman;font-size:13px;">In my understanding, the model should operate as follows when given the settings:</span>
</p>
<ul>
<li><span style="font-family:Times New Roman;font-size:13px;">deltaTClock = 3600s</span>
</li><li><span style="font-family:Times New Roman;font-size:13px;">deltaTtracer = 1800s</span>
</li><li><span style="font-family:Times New Roman;font-size:13px;">deltaTmom = 100s</span>
</li></ul>
<p><span style="font-family:Times New Roman;font-size:13px;">I believed that over one deltaTClock period, the tracer equations would be updated twice, and the momentum equations would be updated 36 times.</span>
</p>
<p><span style="font-family:Times New Roman;font-size:13px;"><br>
</span></p>
<p><span style="font-family:Times New Roman;font-size:13px;">However, I have conducted two different simulations with the following configurations and results:</span>
</p>
<ol>
<li>
<p><span style="font-family:Times New Roman;font-size:13px;">First simulation configuration:</span>
</p>
<ul>
<li><span style="font-family:Times New Roman;font-size:13px;">nIter0 = 0</span> </li><li><span style="font-family:Times New Roman;font-size:13px;">nTimeSteps = 13199</span>
</li><li><span style="font-family:Times New Roman;font-size:13px;">deltaTClock = 3600s</span>
</li><li><span style="font-family:Times New Roman;font-size:13px;">deltaTmom = 0.00001s</span>
</li><li><span style="font-family:Times New Roman;font-size:13px;">deltaTtracer = 3600s</span>
</li></ul>
<strong><span style="font-family:Times New Roman;font-size:13px;"><span style="font-size:13px;">The resu</span><span style="font-size:13px;">lting ice_iceH output seemed more reasonable, with ice formation as expected.</span></span></strong>
</li><li>
<p><span style="font-family:Times New Roman;font-size:13px;">Second simulation configuration:</span>
</p>
<ul>
<li><span style="font-family:Times New Roman;font-size:13px;">nIter0 = 0</span> </li><li><span style="font-family:Times New Roman;font-size:13px;">nTimeSteps = 13199</span>
</li><li><span style="font-family:Times New Roman;font-size:13px;">deltaTClock = 3600s</span>
</li><li><span style="font-family:Times New Roman;font-size:13px;">deltaTmom = 0.001s</span>
</li><li><span style="font-family:Times New Roman;font-size:13px;">deltaTtracer = 1s</span>
</li></ul>
<strong><span style="font-family:Times New Roman;"><span style="font-size:13px;"><span style="font-size:13px;">Surprisingly, this simulation di</span><span style="font-size:13px;">d not produce any ice formation</span></span><span style="font-size:13px;">.</span></span></strong>
</li></ol>
<p><span style="font-family:Times New Roman;"><span style="font-size:13px;">The driving data spans from 2015-06-15 to 2016-12-15 with a time resolution of 3600 seconds.
</span><span style="font-size:13px;">Intuitively, I think that the si</span><span style="font-size:13px;">mulation resul</span><span style="font-size:13px;">ts s</span><span style="font-size:13px;"><span style="font-size:13px;">hould be the same for both configurations
</span><span style="font-size:13px;">, with only a difference in runtime</span><span style="font-size:13px;">.
</span></span><span style="font-size:13px;">I am puzzled by the behavior of these parameters, particularly deltaTtracer and deltaTmom, and how they actually take effect within the model.</span></span>
</p>
<p><span style="font-family:Times New Roman;"><br>
</span></p>
<p><span style="font-family:Times New Roman;"><span style="font-size:13px;">Could you please clarify how these parameters are supposed to function within the model, and whether my understanding aligns with the model's implementation?
</span><br>
</span></p>
<p><span style="font-family:Times New Roman;"><br>
</span></p>
<div><span style="font-family:Times New Roman;"></span><br class="webkit-block-placeholder">
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<p><span style="font-family:Times New Roman;font-size:13px;">I would greatly appreciate any suggestions or guidance you could provide. I am really looking forward to your valuable insights and suggestions.</span>
</p>
<p><span style="font-family:Times New Roman;"><br>
</span></p>
<p><span style="font-family:Times New Roman;font-size:13px;">Best regards,</span>
<span style="font-family:Times New Roman;"><br>
</span></p>
<p><span style="font-family:Times New Roman;"><br>
</span></p>
<p><span style="font-family:Times New Roman;font-size:13px;">Hong Tang</span> </p>
<span style="font-family:Times New Roman;font-size:13px;">University of Chinese Academy of Chinese</span><br>
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