<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">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 face="Courier New" class="">------------------------------------------------------------------------------------<br class=""> Num |<-Name->|Levs| mate |<- code ->|<-- Units -->|<- Tile (max=80c) <br class="">------------------------------------------------------------------------------------<br class=""></font><div class=""><font face="Courier New" class=""> 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 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="">_______________________________________________<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=""></div></body></html>