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<p style="margin-top:0;margin-bottom:0">Hi Edward,</p>
<p style="margin-top:0;margin-bottom:0"> Thanks for your comments. For the constant-wind simulation, I am using free slip boundary conditions on the sides as well as the bottom. The default value of the bottom drag coefficient was zero, I
increased it and the velocities grow at a less rapid rate. I don't get NaN values, at least for the duration of this simulation. I will do some more tests on a larger domain to see if the modified bottom drag is enough to equilibriate the system or whether
I just end up getting NaN values at later times.</p>
<p style="margin-top:0;margin-bottom:0"><br>
</p>
<p style="margin-top:0;margin-bottom:0">I still need to figure out what is wrong with the "constant stress" simulation. To generate the 'zonalwindFile' that goes into 'data', I am following the steps in the gendata.m file in the 'input' folder for the baroclinic
wind gyre tutorial case. <br>
</p>
<p style="margin-top:0;margin-bottom:0"><br>
</p>
<p style="margin-top:0;margin-bottom:0">Thanks for helping!<br>
</p>
<p style="margin-top:0;margin-bottom:0">Sanjiv<br>
</p>
<br>
<br>
<div style="color: rgb(0, 0, 0);">
<hr style="display:inline-block;width:98%" tabindex="-1">
<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>From:</b> MITgcm-support <mitgcm-support-bounces@mitgcm.org> on behalf of Edward W Doddridge <ewd@mit.edu><br>
<b>Sent:</b> Thursday, January 10, 2019 10:19 AM<br>
<b>To:</b> mitgcm-support@mitgcm.org<br>
<b>Subject:</b> Re: [MITgcm-support] Prescribing winds using stress versus bulk formulae</font>
<div> </div>
</div>
<div class="" style="word-wrap:break-word; line-break:after-white-space">Hi Sanjiv,
<div class=""><br class="">
</div>
<div class="">Those plots look an awful lot like your “constant stress” simulation isn’t receiving any wind stress. In comparison the “constant wind” simulation shows a clear imprint of the wind forcing.</div>
<div class=""><br class="">
</div>
<div class="">I suspect that there is something wrong with your setup for the constant stress simulation.</div>
<div class=""><br class="">
</div>
<div class="">You mention that during the constant wind simulation, the jet continues to accelerate until you get NaNs - this can happen if there isn’t enough friction in the model to remove the momentum from the surface forcing. Are you specifying a bottom
drag? Are the sids no-slip? Do you have bathymetry that can support zonal pressure gradients and slow the flow?</div>
<div class=""><br class="">
</div>
<div class="">Regards,</div>
<div class="">Ed<br class="">
<div class=""><br class="x_webkit-block-placeholder">
</div>
<div class="">
<div class="" style="color:rgb(0,0,0); font-family:Palatino; font-size:16px; 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">
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<span class="x_Apple-style-span" style="font-family:Tahoma; font-size:13px"><font class="" size="2" face="Tahoma"><span dir="ltr" class="" style="font-size:10pt"><font class="" size="1"><span class="" style="font-size:13px"><font class="" size="2"><b class="">Edward
Doddridge</b><br class="">
<i class="">Postdoctoral researcher</i></font></span></font></span></font></span></span></div>
<div class="" style="color:rgb(0,0,0); font-family:Palatino; font-size:16px; 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">
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Atmospheric and Planetary Sciences</i></font></span></font></span></font></span></span></div>
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Institute of Technology</i></font></span></font></span></font></span></span></div>
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</i></font></span></font></span></font></span></span></div>
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<blockquote type="cite" class="">
<div class="">On 9 Jan 2019, at 15:13, Sanjiv Ramachandran <<a href="mailto:sramachandran@umassd.edu" class="">sramachandran@umassd.edu</a>> wrote:</div>
<br class="x_Apple-interchange-newline">
<div class="">
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<div class="" style="margin-top:0px; margin-bottom:0px">Hi Martin,</div>
<div class="" style="margin-top:0px; margin-bottom:0px"> I turned off the bulk forcing formulae in EXF_options.h as you had suggested:</div>
<div class="" style="margin-top:0px; margin-bottom:0px"><br class="">
</div>
<div class="" style="margin-top:0px; margin-bottom:0px">#undef ALLOW_ATM_TEMP<br class="">
</div>
<div class="">#define ALLOW_ATM_WIND<br class="">
#undef ALLOW_DOWNWARD_RADIATION<br class="">
<br class="">
The data.exf file now reads (showing only the relevant bits):<br class="">
<div class=""> &EXF_NML_03<br class="">
# uwindconst = -1.0,<br class="">
# atempconst = 298.0,<br class="">
# aqhconst = 0.007,<br class="">
swfluxconst= 0.0,<br class="">
hfluxconst = 0.0,<br class="">
sfluxconst = 0.0, <br class="">
&</div>
<br class="">
I am still having the same problems, which is that the jet keeps accelerating in the simulation with constant winds until I get NaN values.<span class="x_Apple-converted-space"> </span><br class="">
<br class="">
(i) After the changes listed above, my EXF diagnostics file shows zero values for 'EXFswnet' and 'EXFqnet'. The variables 'EXFhs', 'EXFhl' and 'EXFlwnet' are not zero but presumably that is okay because I am using option 1 (Sec.B, EXF_options.h) to specify
the fluxes in data.exf.<span class="x_Apple-converted-space"> </span><br class="">
<br class="">
(ii) I am attaching a few plots at the link below from the two simulations, one with constant \tau and the other with constant winds that uses the 'exf' package to compute \tau using exchange coefficients. The topmost plot on the first page shows the effective
wind stress is much smaller than the value I am using in the constant-tau simulations. This is true at all times for the constant-wind simulation, based on the values in the EXF diagnostics file. Yet, the zonal velocity ('U' in my plots) is very different
in the two simulations.<br class="">
(<u class="">Note</u>: I have modified the exf_init_varia.F file to specify an initial 'uwind' profile that is zero towards the walls. Specifying a constant 'uwind' value in data.exf yields undesirable upwelling and downwelling at the south and north walls).<span class="x_Apple-converted-space"> </span><br class="">
Here is the link for the plots:<br class="">
<br class="">
<a disabled="true" tabindex="-1" href="https://www.dropbox.com/s/ut9fqhy826a0hys/tau_vs_wind_check.pdf?dl=0" class="x_OWAAutoLink">https://www.dropbox.com/s/ut9fqhy826a0hys/tau_vs_wind_check.pdf?dl=0</a><br class="">
</div>
<p class="" style="margin-top:0px; margin-bottom:0px"></p>
<div class="" style="margin-top:0px; margin-bottom:0px"><br class="">
</div>
<div class="" style="margin-top:0px; margin-bottom:0px">Does 'exf' need to know whether I am using non-periodic BCs in the meridional direction? <br class="">
</div>
<div class="" style="margin-top:0px; margin-bottom:0px"><br class="">
</div>
<div class="" style="margin-top:0px; margin-bottom:0px">Thanks!<br class="">
</div>
Sanjiv<br class="">
<br class="">
<br class="">
<div class="" style="">
<hr disabled="true" tabindex="-1" class="" style="display:inline-block; width:1259.296875px">
<div id="x_divRplyFwdMsg" dir="ltr" class=""><font class="" style="font-size:11pt" face="Calibri, sans-serif"><b class="">From:</b><span class="x_Apple-converted-space"> </span>MITgcm-support <<a href="mailto:mitgcm-support-bounces@mitgcm.org" class="">mitgcm-support-bounces@mitgcm.org</a>>
on behalf of Martin Losch <<a href="mailto:Martin.Losch@awi.de" class="">Martin.Losch@awi.de</a>><br class="">
<b class="">Sent:</b><span class="x_Apple-converted-space"> </span>Friday, January 4, 2019 4:40 AM<br class="">
<b class="">To:</b><span class="x_Apple-converted-space"> </span>MITgcm Support<br class="">
<b class="">Subject:</b><span class="x_Apple-converted-space"> </span>Re: [MITgcm-support] Prescribing winds using stress versus bulk formulae</font>
<div class=""> </div>
</div>
<div class="" style="word-wrap:break-word; line-break:after-white-space">Hi Sanjiv,
<div class=""><br class="">
</div>
<div class="">I think that with your settings, you’ll have some unbalanced thermal forcing (that has nothing to do with the wind).</div>
<div class=""><br class="">
</div>
<div class="">You can check with the diagnostics package what the individual fluxes are:</div>
<div class=""><br class="">
</div>
<font class="" face="Courier New">------------------------------------------------------------------------------------<br class="">
Num |<-Name->|Levs| mate |<- code ->|<-- Units -->|<- Tile (max=80c) <br class="">
------------------------------------------------------------------------------------<br class="">
</font>
<div class=""><font class="" face="Courier New"> 187 |EXFhs | 1 | |SM U1|W/m^2 |Sensible heat flux into ocean, >0 increases theta<br class="">
188 |EXFhl | 1 | |SM U1|W/m^2 |Latent heat flux into ocean, >0 increases theta<br class="">
189 |EXFlwnet| 1 | |SM U1|W/m^2 |Net upward longwave radiation, >0 decreases theta<br class="">
190 |EXFswnet| 1 | |SM U1|W/m^2 |Net upward shortwave radiation, >0 decreases theta<br class="">
191 |EXFlwdn | 1 | |SM U1|W/m^2 |Downward longwave radiation, >0 increases theta<br class="">
192 |EXFswdn | 1 | |SM U1|W/m^2 |Downward shortwave radiation, >0 increases theta<br class="">
193 |EXFqnet | 1 | |SM U1|W/m^2 |Net upward heat flux (turb+rad), >0 decreases theta<br class="">
194 |EXFtaux | 1 | |UM U1|N/m^2 |zonal surface wind stress, >0 increases uVel<br class="">
195 |EXFtauy | 1 | |VM U1|N/m^2 |meridional surface wind stress, >0 increases vVel<br class="">
196 |EXFuwind| 1 | |UM U1|m/s |zonal 10-m wind speed, >0 eastward<br class="">
197 |EXFvwind| 1 | |VM U1|m/s |meridional 10-m wind speed, >0 northward<br class="">
198 |EXFwspee| 1 | |SM U1|m/s |10-m wind speed modulus ( >= 0 )<br class="">
199 |EXFatemp| 1 | |SM U1|degK |surface (2-m) air temperature<br class="">
200 |EXFaqh | 1 | |SM U1|kg/kg |surface (2-m) specific humidity<br class="">
201 |EXFevap | 1 | |SM U1|m/s |evaporation, > 0 increases salinity<br class="">
202 |EXFpreci| 1 | |SM U1|m/s |precipitation, > 0 decreases salinity<br class="">
203 |EXFsnow | 1 | |SM U1|m/s |snow precipitation, > 0 decreases salinity<br class="">
204 |EXFempmr| 1 | |SM U1|m/s |net upward freshwater flux, > 0 increases salinity<br class="">
205 |EXFpress| 1 | |SM U1|N/m^2 |atmospheric pressure field<br class="">
206 |EXFroff | 1 | |SM U1|m/s |river runoff, > 0 decreases salinity<br class="">
</font><br class="">
You’ll probably find that EXFhs, EXFhl, EXFlwnet will be non-zero. I order to avoid that, you’d have to turn off the bulk formulae and radiation code:</div>
<div class="">#undef ALLOW_DOWNWARD_RADIATION</div>
<div class="">#undef ALLOW_BULKFORMULAE</div>
<div class="">See the default pkg/exf/EXF_OPTIONS.h Section (B) Surface buoyance flux. You want option (1), that would be similar to not using exf, except for the wind fields.</div>
<div class=""><br class="">
</div>
<div class="">Martin<br class="">
<br class="">
<blockquote type="cite" class="">On 3. Jan 2019, at 22:53, Sanjiv Ramachandran <<a disabled="true" tabindex="-1" href="mailto:sramachandran@umassd.edu" class="">sramachandran@umassd.edu</a>> wrote:<br class="">
<br class="">
Hi all,<br class="">
I am some questions about prescribing winds through the 'exf' package. My initial condition is a shallow mixed layer in geostrophic balance (based on the 'MLAdjust' test case) with a zonal jet whose peak value at the surface is initially 0.24 m/s. <br class="">
<br class="">
When I turn off the 'exf' package, and prescribe a wind stress = 0.05 N/m2 through the 'zonalWindFile' variable in 'data', the model runs without problems for 50 days.<br class="">
<br class="">
When I turn on the 'exf' package with a constant wind of 3 m/ the zonal velocities in the domain keep increasing with time until I get NaN values around day 30. I am not sure why this is happening as the wind stress in the second case is much weaker. Winds
of 3 m/s, assuming an exchange coefficient (Cd) of 1.2e-3, and rho_air=1.22 kg/m3, correspond to a wind stress of 0.013 N/m2. <br class="">
<br class="">
For the simulation with 'exf' turned on, I have enabled the following three options in EXF_OPTIONS.h:<br class="">
#define ALLOW_ATM_TEMP<br class="">
#define ALLOW_ATM_WIND<br class="">
#define ALLOW_DOWNWARD_RADIATION<br class="">
<br class="">
I am pasting below the relevant parameters from some of the data files for the simulation with 'exf' turned on. Any pointers on where I might be erring would be greatly appreciated. <br class="">
<br class="">
--------------------------data.pkg---------------------------------------------<br class="">
# Packages<br class="">
&PACKAGES<br class="">
useEXF = .TRUE.,<br class="">
useCAL = .TRUE.,<br class="">
useMNC = .TRUE.,<br class="">
useKPP = .TRUE.,<br class="">
useDiagnostics=.TRUE.,<br class="">
&<br class="">
----------------------------data.kpp---------------------------------------------<br class="">
# KPP parameters<br class="">
&KPP_PARM01<br class="">
KPPmixingMaps = .FALSE.,<br class="">
KPPwriteState = .TRUE.,<br class="">
KPP_ghatUseTotalDiffus=.TRUE.,<br class="">
kpp_dumpFreq = 2160000., <br class="">
&<br class="">
---------------------------data.exf------------------------------------------------<br class="">
&EXF_NML_01<br class="">
# useExfCheckRange = .TRUE.,<br class="">
useAtmWind=.TRUE.,<br class="">
readStressOnCgrid=.TRUE.,<br class="">
# repeatPeriod = 2678400.0,<br class="">
# exf_iprec = 32,<br class="">
#<br class="">
&<br class="">
<br class="">
&EXF_NML_02<br class="">
hfluxfile = ' ',<br class="">
sfluxfile = ' ',<br class="">
ustressfile = ' ',<br class="">
vstressfile = ' ',<br class="">
atempfile = ' ',<br class="">
aqhfile = ' ',<br class="">
uwindfile = ' ',<br class="">
vwindfile = ' ',<br class="">
evapfile = ' ',<br class="">
precipfile = ' ',<br class="">
lwfluxfile = ' ',<br class="">
swfluxfile = ' ',<br class="">
lwdownfile = ' ',<br class="">
swdownfile = ' ',<br class="">
runoffFile = ' ',<br class="">
climsstfile = ' ',<br class="">
climsssfile = ' ',<br class="">
&<br class="">
<br class="">
&EXF_NML_03<br class="">
uwindconst = -3.0,<br class="">
atempconst = 298.0, # approx. 0.5 degree cooler than the SST<br class="">
swfluxconst= 0.0, # zeroed out for debugging<br class="">
lwdownconst = 0.0, # zeroed out for debugging<br class="">
&<br class="">
<br class="">
----------------------------------------data-------------------------------------<br class="">
&PARM01<br class="">
viscAr=1.E-5,<br class="">
viscC4leith = 1.85,<br class="">
viscC4leithD = 1.85, <br class="">
viscC4smag = 1.,<br class="">
viscA4GridMax = 1.,<br class="">
useFullLeith=.TRUE.,<br class="">
no_slip_sides=.FALSE.,<br class="">
no_slip_bottom=.FALSE.,<br class="">
vectorInvariantMomentum=.TRUE.,<br class="">
ivdc_kappa=0.,<br class="">
implicitDiffusion=.TRUE.,<br class="">
implicitViscosity=.TRUE.,<br class="">
f0=4.E-5, # corresponds to lat. = 16 N<br class="">
beta=1.E-11,<br class="">
useJamartWetPoints=.TRUE.,<br class="">
eosType='LINEAR',<br class="">
# Temperature <br class="">
tAlpha=3.16E-4,<br class="">
# Salinity <br class="">
sBeta =6.32E-4,<br class="">
gravity=9.81,<br class="">
rhoNil=1027.,<br class="">
rigidLid=.FALSE.,<br class="">
implicitFreeSurface=.TRUE.,<br class="">
staggerTimeStep=.TRUE.,<br class="">
tempAdvScheme=33,<br class="">
saltAdvScheme=33,<br class="">
readBinaryPrec=64,<br class="">
writeBinaryPrec=64,<br class="">
nonHydrostatic=.FALSE.,<br class="">
&<br class="">
<br class="">
&PARM02<br class="">
cg2dMaxIters=1000,<br class="">
cg2dTargetResidual=1.E-11,<br class="">
cg3dMaxIters=40,<br class="">
cg3dTargetResidual=1.E-9,<br class="">
&<br class="">
<br class="">
&PARM03 <br class="">
cAdjFreq=0.,<br class="">
&<br class="">
<br class="">
---------------------------------------------------------<br class="">
<br class="">
Thanks,<br class="">
Sanjiv<br class="">
<br class="">
<br class="">
<br class="">
<br class="">
<br class="">
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