1. Physics Implementation Three_level Structure What you might need to do
WRF Model:
Physics Implementation
Shu-hua Chen
NCAR/AFWA
(UC Davis, Sep.)
OUTLINE F S C I Y H P R W
Physics Schemes
Three_level Structure
Rules for WRF physics
WRF Physics Features
WRF Language
What you might need to do

2. Scheme Selection W F R Simple schemes for operationY H P R W
Simple schemes for operation
Complicated schemes for research

3. Physics Schemes W F R P I H C Y S Physical Process Available
Microphysics Kessler, Lin et al. ,
Ncloud3, Ncloud5
Cumulus KF, BMJ
Subgrid scale turbulence TKE, Smagrinsky,
Constant K
Radiation RRTM(L), Dudhia(S),
Goddard(S)
PBL MRF
Surface layer Similarity theory
Land-surface layer layer soil temperature

4. • Physics Interface Design W F R Simple User friendly
Different dynamics cores
Three-level structure
=>

5. Three-level StructureF S C I Y H P R W
Solver
Physics_driver
SELECT CASE (CHOICE)
CASE ( NOPHY )
CASE ( SCHEME1 )
CALL XXX
CASE ( SCHEME2 )
CALL YYY .
CASE DEFAULT
END SELECT
Individual physics scheme
( XXX )

6. W F R . . . P I H C Y S phy_prep phy_init Radiation_driver pbl_driver…
microphysics_driver
Radiation_driver
Cumulus_driver
pbl_driver
INIT .
WRF
solve_rk …
moist_physics_prep
ADV TENDENCIES .
ADVANCE VARS .

7. phy_prep & moist_physics_prepF S C I Y H P R W
• Decouple variables
• Convert variables from C grid
to A grid

8. Three-level StructureF S C I Y H P R W
Solver
Physics_driver
SELECT CASE (CHOICE)
CASE ( NOPHY )
CASE ( SCHEME1 )
CALL XXX
CASE ( SCHEME2 )
CALL YYY .
CASE DEFAULT
END SELECT
Individual physics scheme
( XXX )

9. Physics Standard InterfaceW
SELECT CASE (CHOICE)
CASE ( NOPHY )
CASE ( SCHEME1 )
CALL XXX(…)
CASE ( SCHEME2 )
CALL YYY(…) .
CASE DEFAULT
END SELECT
Physics_driver

10. Three-level StructureF S C I Y H P R W
Solver
Physics_driver
SELECT CASE (CHOICE)
CASE ( NOPHY )
CASE ( SCHEME1 )
CALL XXX
CASE ( SCHEME2 )
CALL YYY .
CASE DEFAULT
END SELECT
Individual physics scheme
( XXX )

11. Three Sets of DimensionsC I Y H P R W
Domain size:
ids, ide, jds, jde, kds, kde
Memory size:
ims, ime, jms, jme, kms, kme
Tile size:
its, ite, jts, jte, kts, kte

12. Logical Domain (ids,kds,jds)F S C I Y H P R W
(ids,ide)

13. Memory size (ims,kms,jms)F S C I Y H P R W
patch
(ids,ide)
halo
(ims,ime)

14. Tile size (its,kts,jds) W F R P I H C Y S tile (its,ite) (ims,ime)
halo
(ims,ime)
tile
(its,ite)

15. W F R . . . P I H C Y S phy_prep phy_init Radiation_driver pbl_driver…
microphysics_driver
Radiation_driver
Cumulus_driver
pbl_driver
INIT .
WRF
solve_rk …
moist_physics_prep
ADV TENDENCIES .
ADVANCE VARS .

16. Rules for WRF Physics F S C I Y H P R W
Coding rules

17. Coding Rules W F R P I H C Y S 1. F90
Replace continuation characters in the 6th column with f90 continuation `&‘ at end of previous line
Subroutine kessler(QV, T,
& its,ite,jts,jte,kts,kte,
& ims,ime,jms,jme,kms,kme,
& ids,ide,jds,jde,kds,kde)
F77
Subroutine kessler(QV, T, &
its,ite,jts,jte,kts,kte,&
ims,ime,jms,jme,kms,kme,&
ids,ide,jds,jde,kds,kde )
F90

18. Coding Rules W F R P I H C Y S 1. F90
Replace continuation characters in the 6th column with f90 continuation `&‘ at end of previous line
b)Replace the 1st column `C` for comment with `!`
c This is a test
F77
! This is a test
F90

19. Coding Rules W F R P I H C Y S 1. F90 2. No common block
Replace continuation characters in the 6th column with f90 continuation `&‘ at end of previous line
b)Replace the 1st column `C` for comment with `!`
2. No common block
3. Use “ implicit none ”
4. Use “ intent ”
5. Variable dimensions and do loops

20. Rules for WRF Physics W F R Coding rules One scheme one module P I H C
Naming rules

21. Naming Rules W ex, module_cu_kf.F F R cu is for cumulusY H P R W
module_yy_xxx.F (module)
yy = ra is for radiation bl is for PBL
cu is for cumulus
mp is for microphysics.
xxx = individual scheme
ex, module_cu_kf.F

22. Naming Rules W F R ex, RTHBLTEN P I H C Y S cu is for cumulus
RXXYYTEN (tendencies)
XX = variable (th, u, v, qv, qc, … )
YY = ra is for radiation bl is for PBL
cu is for cumulus
ex, RTHBLTEN

23. Rules for WRF Physics W F R One scheme one module Naming rules P I H C
Coding rules
One scheme one module
Naming rules
Vectorized code preferred
( might depend on which
physics component )

24. WRF Physics Features W F R • Unified global constatnts P I H C Y S
(module_model_constants.F)
REAL , PARAMETER :: r_d = 287.
REAL , PARAMETER :: r_v = 461.6
REAL , PARAMETER :: cp = 7.*r_d/2.
REAL , PARAMETER :: cv = cp-r_d .

25. WRF Physics Features W F R • Unified global constatnts
(module_model_constants.F)
• Unified common calculations
(saturation mixing ratio)
• Vertical index (kms is at the bottom)

26. Three-level StructureF S C I Y H P R W
Solver
Physics_driver
SELECT CASE (CHOICE)
CASE ( NOPHY )
CASE ( SCHEME1 )
CALL XXX
CASE ( SCHEME2 )
CALL YYY .
CASE DEFAULT
END SELECT
Individual physics scheme
( XXX )

27. WRF Physics Features W F R • Unified global constatnts
(module_model_constants.F)
• Unified common calculations
(saturation mixing ratio)
• Vertical index (kms is at bottom)
• kme = kte + 1 (physics)
kme = kte (dynamics)

28. WRF Language W F R • Patch, tile, ….S C I Y H P R W
• Patch, tile, ….
• Moisture field, moist(i,k,j,?), is 4D
• ? = P_QV, P_QC, P_QR, P_QI,P_QS,
P_QG (module_state_description.F)
• PARAM_FIRST_SCALAR
IF ( P_QI .ge. PARAM_FIRST_SCALAR )
. . .

29. W P_QV, P_QC, P_QR, … F R Registry P I H C Y S
package kesslerscheme mp_physics==1 - moist:qv,qc,qr
package linscheme mp_physics== moist:qv,qc,qr,qi,qs,qg
package ncepcloud mp_physics==3 - moist:qv,qc,qr
package ncepcloud mp_physics==4 - moist:qv,qc,

30. What you might need to do ?F S C I Y H P R W
Run existing codes
(namelist.input)
Physics Buffet
mp_physics = 2,
ra_lw_physics = 1,
ra_sw_physics = 1,
bl_sfclay_physics = 1,
bl_surface_physics = 1,
bl_pbl_physics = 1,
cu_physics = 1,

31. What you might need to do ?F S C I Y H P R W
Run existing codes
Modify existing codes
Plug in your own codes

32. WRF Development Team F S C I Y H P R W