| 145 | |
| 146 | == Coupled model CRUNs == |
| 147 | |
| 148 | We compare a 2day NRUN with a 2x1-day CRUN in u-ak282debug and u-ak282debugCRUN. |
| 149 | |
| 150 | Inspecting the solver.stat file, this reveals that NMEO seems to diverge on the first TS immediately after the restart i.e. TS 33! |
| 151 | Why? |
| 152 | We have other models (e.g. the stand-alone NEMO-CICE-MEDUSA which don't. |
| 153 | |
| 154 | So this could arise from the coupling fields coming from the atmos at TS0, but the atmos dumps are identical at day 1 and checking the most likely contenders (PCO2 and dust) shows they're fine at teh start of day 2. |
| 155 | |
| 156 | Comparing the ocean.output files at the start of day 2 leads us to fishy looking things related to TOP/MEDUSA since we have a message |
| 157 | ' New shortwave to sample for TOP at time kt = ' occurring at different timesteps for each run. In the NRUN case this occurs at TS 36 and in the CRUN case it occurs at TS 38! |
| 158 | This leads us to trcstp.F90 which contains a flaky looking |
| 159 | bit of code: |
| 160 | {{{ |
| 161 | iseclast = nsec_year + nsec1jan000 |
| 162 | llnew = ( iseclast - isecfst ) > INT( rdt_sampl ) ! new shortwave to store |
| 163 | |
| 164 | IF( kt /= nittrc000 .AND. llnew ) THEN |
| 165 | IF( lwp ) WRITE(numout,*) ' New shortwave to sample for TOP at time kt = ', kt, & |
| 166 | & ' time = ', (iseclast+rdt*nn_dttrc/2.)/3600.,'hours ' |
| 167 | isecfst = iseclast |
| 168 | DO jn = 1, nb_rec_per_days - 1 |
| 169 | qsr_arr(:,:,jn) = qsr_arr(:,:,jn+1) |
| 170 | ENDDO |
| 171 | qsr_arr (:,:,nb_rec_per_days) = qsr(:,:) |
| 172 | qsr_mean(:,: ) = SUM( qsr_arr(:,:,:), 3 ) / nb_rec_per_days |
| 173 | ENDIF |
| 174 | }}} |
| 175 | |
| 176 | That can never give the same results for NRUNS and CRUNS! |
| 177 | This condition arises at the 6th timestep after a restart and every 5 timesteps thereafter. |
| 178 | So in the restart case it occurs at TS=38, 43, 48, 53 etc while in the NRUN case is arises at TS=36, 41, 46, 51 etc. |
| 179 | |
| 180 | This comes from the vn3.6 NEMO_stable branch via the GO6 branch, and is not specific to the MEDUSA branch. But it looks utter garbage. |
| 181 | |
| 182 | The description says "In coupled mode, the sampling is done at every coupling frequency", which is not what happens at all because, |
| 183 | with a 45 minute TS and a coupling frequency of 3 hours which we have in our model: |
| 184 | |
| 185 | * The first sample is taken at TS 6 after a start i.e. 4.5 hours |
| 186 | * subsequent samples occur at 3.75 hours not the 3 hours it should do! |
| 187 | |
| 188 | I think this should be sampling, consistently at TS = 0, 4, 8.... 32.... (though 32 shouldn't matter in the case of day 1 of the CRUN) or something like that. |
| 189 | |
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