ARSC/IARC Report DOD/RACM Workshop, December Juanxiong He 1,2 Greg Newby 1 1. Arctic Region Supercomputing Center 2. International Arctic Research Center

The regional WRF coupling with regional POP2, regional CICE and dlnd Setting: WRF(wr50a, 276x206x35, 50km, dt=150s, CAM/Monin- Obukhov/YSU/Kain-Fritsch, Specified boundary condition) POP2/CICE (ar9v2, 1380x1080x45, ~9km, dt=6min) coupling every 30 minutes Cold start at _00:00:00 Length > 5 months

Cold feedback Parallel bug Import climatology SST into the extended grid Solve the cold feedback

initial status – first test seaice at _00:00:00 surface skin temperature at _00:00:00 Constant SST

severe cold feedback sea ice at _00:00:00 surface skin temperature at _00:00:00

Fix the parallel bug The bug: mpi_cart_create in the WRF returns two new communicators. According the MPI standard, shall only one new communicator be generated. Test the program on the pingo and with the other MPI libraries such as openmpi and mpich , the error still exists. It confirms the error lies in the WRF. The bug distorts the simulation especially over the boundary. Move the processors division function from module_dm.F to seq_comm_mct.F90

Parallel - Distort the simulation discontinuity

After the correction Coupling Standard WRF

Unreasonable latent heat near the lateral boundary

T

u

v

Solve the severe cold feedback problem The integration order of the physical schemes contributes it. Readjust the integration order of the physical schemes Replace constant SST in the extended grid with the climatology SST

The integration order of the physical schemes Surface layer Radiation Pbl The previouseThe adjustment Surface layer Pbl Radiatio n

initial status – second test seaice at _00:00:00 surface skin temperature at _00:00:00 discontinuity

Seaice – after one month integration seaice of the coupling at _00:00:00 Seaice from reanalysis and interpolated by pure WRF initialization at _00:00:00 excess

Seaice – after two months integration seaice at _00:00:00 Seaice from reanalysis and interpolated by pure WRF initialization at _00:00:00 growth

Seaice – after three months integration seaice at _00:00:00 Seaice from reanalysis and interpolated by pure WRF initialization at _00:00:00 decrease

Seaice – after four months integration seaice at _00:00:00 Seaice from reanalysis and interpolated by pure WRF initialization at _00:00:00 Shrink

Surface skin temperature - second test surface skin temperature at _00:00:00 surface skin temperature at _00:00:00 discontinuity dlnd seems unchanged

Sea level pressure - snapshot slp at _00:00:00 slp at _00:00:00

Parallel computation Very slow in a very small cpu resources WRF - 1d/24m/64p, 1d/12m/128p, 1d/7m/256p POP2 - 1d/17m/64p, 1d/10m/128p, 1d/7m/256p CICE - 1d/8m/64p, 1d/5m/128p, 1d/3m/256p CPL - 1d/3m/64p, 1d/1m/128p, 1d/<1m/256p RACM - 1d/52m/64p, 1d/28m/128p, 1d/17m/256p Concurrency/fully sequential The fully sequential – 1d/28m/128p concurrency – 1d/33m/128p competitions among the communication, the acceleration and the concurrency A very small cpu resources, need to scale up more than 1024 processors

Next WRF, VIC, POP2 and CICE fully regional coupling, well tune and plan productive run carefully Optimization and Scale up to more than 1024 processors

Thank you!