1. GEMDM: SOFTWARE/PERFORMANCE
Michel Desgagné
Recherche en Prévision Numérique
Environment Canada - MSC/RPN
Environment Canada

2. OUTLINE Grid configurations LAM implementation
Distributed Memory implementation: GEMDM

3. Gem_settings.nml
&grid Grd_typ_S = 'LU' , Grd_ni = , Grd_nj = 60 , Grd_xlon = , Grd_xlat = 45., Grd_xlon = , Grd_xlat = 45., Grd_iref = , Grd_jref = 40 , Grd_lonr = , Grd_latr = 20., Grd_dx = , Grd_dy = 1.9, / &ptopo PtOPo_Npex = , PtoPo_npey = 1 , Ptopo_nblocx = , Ptopo_nblocy = 1 , / &gement / &gem_cfgs / &physics_cfgs phy_pck_version = 'RPN-CMC_4.5', /

4. Grd_xlon1 = 180. Grd_xlat1 = 0. Grd_xlon2 = 270. Grd_xlat2 = 0.,
270.0, 0.0
180.0, 0.0 0.
360.
-90.
90.
Grd_typ_S = ‘GU' , Grd_ni = , Grd_nj = 30 , Grd_xlon = , Grd_xlat = 45., Grd_xlon = , Grd_xlat = 45.,
Grd_typ_S = ‘GV' , Grd_ni = , Grd_nj = 30 ,
Grd_nila = , Grd_njla = 6 ,
Grd_dx = , Grd_dy = 0.9,
Grd_xlon = , Grd_xlat = 45., Grd_xlon = , Grd_xlat = 45.,
270.0, 0.0
270.0, 90.0
Lat` != Lat
Lon` != Lon
270.0, 0.0
0.0, 0.0 0.
360.
-90.
90.
Lat` = Lat
Lon` != Lon
270.0, 45.0
0.0, 45.0
Grd_xlon1 = Grd_xlat1 = 0. Grd_xlon2 = Grd_xlat2 = 0.,

5. Software: grille -xrec
360.0,90.0
Grd_ni = 30 , Grd_nj = 30
Grd_iref= 15 , Grd_jref= 15 Grd_lonr= 180., Grd_latr= 0.
Grd_ni = 30 , Grd_nj = 20
Grd_iref= 1 , Grd_jref= 20 Grd_lonr= 40. , Grd_latr= 0.
Grd_ni = 10 , Grd_nj = 30
Grd_iref= 1 , Grd_jref= 1 Grd_lonr= 300., Grd_latr= 20.
0.0,-90.0
Grd_typ_S = 'LU' , Grd_xlon1 = , Grd_xlat = 45., Grd_xlon2 = , Grd_xlat = 45., Grd_dx = , Grd_dy = 1.9,

6. GEM: A short description
Finite-differences on Arakawa C lat-lon horizontal grid
Hydrostatic pressure s-type vertical coordinate with hybrid formulation
high-order horizontal diffusion
Full CMC/RPN physics package
Global or LAM lat-lon grid point model
Primitive equations Non-Hydrostatic
2-time-level fully implicit Semi-Lag discretization
Elliptic problem: direct solver (data transpose in DM configurations)

7. An Acid Test for LAM Regional Modelling: A Theoretical Discussion A
An Acid Test for LAM Regional Modelling: A Theoretical Discussion A. Staniforth, 1995 (Meteor. Atmos. Phys.)
At same horizontal and temporal resolution, how well can
a LAM reproduce the solution of a large domain on
any smaller subdomain
6 timesteps GU
6 timesteps LU
Is it that important?
Our current Acid test includes:
The whole diabatic kernel + horizontal diffusion

8. Layout (2) Free Domain Computational zone Never Used
Forced Boundary Conditions (7 points)
Not Used
if LAM
BCs for Elliptic Problem V
OB-SLT
Blending Zone:
s= p*ext + (1-p)int
p= cos**2 ( ) U
0.0
1.0
Free Domain
Free Domain
OB-SLT
Computational zone 1
L_ni
Halo xchg with neighboring PEs