1. Add a Physics Scheme into WRF Model
Shu-hua Chen
UC Davis/AFWA
Physics implementation features
Adding a physics scheme

2. Three Sets of Dimensions
Domain size:
ids, ide, jds, jde, kds, kde
Memory size:
ims, ime, jms, jme, kms, kme
Tile size:
its, ite, jts, jte, kts, kte

3. Rules for WRF Physics
Naming rules

4. Naming Rules ex, module_cu_kf.F cu is for cumulus
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

5. Naming Rules ex, RTHBLTEN 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

6. Rules for WRF Physics Naming rules One scheme one module
Coding rules (later)

7. WRF Physics Features • Unified global constatnts
(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 .

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

9. WRF Language • 4D Moisture field, moist(i,k,j,?)
? = P_QV (water vapor)
P_QC (cloud water)
P_QI (cloud ice)
P_QR (rain)
P_QS (snow)
P_QG (graupel)
(module_state_description.F)

10. WRF Language • 4D Moisture field, moist(i,k,j,?) • PARAM_FIRST_SCALAR
IF ( P_QI .ge. PARAM_FIRST_SCALAR )
(the memory of cloud ice is allocated)
. . .

11. Implement a new physics scheme
Prepare your code
Create a new module
Declare new variables and
a new package in Registry
Modify namelist
Do initialization
Modify solve_em.F (solve_eh.F)
Modify phy_prep (module_em.F)

12. Implement a new physics scheme
Modify cumulus_driver.F
Modify physics_drive.int
Modify calculate_phy_ten
(module_em.F)
Modify phy_cu_ten
(module_physics_addtendc.F)
Modify Makefile
Compile and test

13. Prepare your code
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

14. Prepare your code
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

15. Prepare your code 1.F90 2.No common block F77 common/var1/T,q,p, … F90
Subroutine sub(T,q,p, ….)
real,intent(out), &
dimension(ims:ime,kms:kme,jms:jme):: T,q,p
F90

16. Prepare your code 1.F90 2.No common block 3.Use “ implicit none ”
4.Use “ intent ”
Subroutine sub(T,q,p, ….)
real,intent(out), &
dimension(ims:ime,kms:kme,jms:jme):: T real,intent( in), &
dimension(ims:ime,kms:kme,jms:jme):: q
real,intent(inout), &
dimension(ims:ime,kms:kme,jms:jme):: p

17. Prepare your code 1.F90 2.No common block 3.Use “ implicit none ”
4.Use “ intent ”
5.Variable dimensions
Subroutine sub(glo,….)
real,intent(out), &
dimension(ims:ime,kms:kme,jms:jme):: glo real,dimension(its:ite,kts:kte,jts:jte):: loc

18. Prepare your code 1.F90 2.No common block 3.Use “ implicit none ”
do j = jts, jte
do k = kts, kte
do i = its, ite
...
enddo
3.Use “ implicit none ”
4.Use “ intent ”
5.Variable dimensions
6.Do loops

19. Implement a new physics scheme
Create a new module
ex, module_cu_chen.F (put all your codes in)
Go Registry and declare a new package
(and new variables) (WRFV1/Registry)
package kfscheme cu_physics==1 - -
package bmjscheme cu_physics==2 - -
package chenscheme cu_physics==3 - -

20. Implement a new physics scheme
Create a new module
ex, module_cu_chen.F (put all your codes in)
Go Registry and declare a new package
(and new variables) (WRFV1/Registry)
Cloud microphysics
package kesslerscheme mp_physics==1 - moist:qv,qc,qr
package linscheme mp_physics==2 - moist:qv,qc,qr,qi,qs,qg
package ncepcloud mp_physics==3 - moist:qv,qc,qr
package ncepcloud mp_physics==4 - moist:qv,qc,

21. Implement a new physics scheme
Create a new module
ex, module_cu_chen.F (put all your codes in)
Go Registry and declare a new package
(and new variables) (WRFV1/Registry)
Modify namelist.input and assign
cu_physics = 3

22. (module_physics_init.F)
(dyn_em)
(start_em.F)
(phys)
(module_physics_init.F)
phy_init
cu_init *
start_domain_em
INIT
(dyn_em)
WRF
solve_em
…….

23. phys/module_physics_init.F
Pass new variables down to cu_init

24. (module_physics_init.F)
(dyn_em)
(start_em.F)
(phys)
(module_physics_init.F)
phy_init
cu_init *
start_domain_em
INIT
(dyn_em)
WRF
solve_em
…….

25. phys/module_physics_init.F
Pass new variables down to cu_init
Go subroutine cu_init
Include the new module and create
a new SELECT case

26. phys/module_physics_init.F
Subroutine cu_init(…) .
USE module_cu_kf USE module_cu_bmj
USE module_cu_chen
cps_select: SELECT CASE(config_flags%cu_physics)
CASE (KFSCHEME) CALL kfinit(...) CASE (BMJSCHEME)
CALL bmjinit(...)
CASE DEFAULT
END SELECT cps_select
Match the package name in Registry
CASE (CHENSCHEME)
CALL cheninit(...)
Put into
module_cu_chen.F

27. . . phy_prep phy_init solve_em INIT DYNAMICS moist_physics_prep … WRF

28. phy_prep/moist_physics_prep
• Calculate required variables
• Convert variables from C grid
to A grid

29. . . phy_prep phy_init radiation_driver pbl_driver cumulus_driver…
radiation_driver
INIT
pbl_driver
cumulus_driver
chencps
WRF
solve_em . …
DYNAMICS .
moist_physics_prep
microphysics_driver

30. Three-level structure
solve_em
Physics_driver
SELECT CASE (CHOICE)
CASE ( NOPHY )
CASE ( SCHEME1 )
CALL XXX
CASE ( SCHEME2 )
CALL YYY .
CASE DEFAULT
END SELECT
Individual physics scheme
( XXX )

31. cumulus_driver.F Go physics driver (cumulus_driver.F)
Include the new module
and create a new SELECT CASE in driver
Check available variables in drivers
(variables are explained inside drivers)

32. cumulus_driver.F . USE module_cu_kf USE module_bmj_kf
Subroutine cumulus_driver .
USE module_cu_kf USE module_bmj_kf
USE module_cu_chen
cps_select: SELECT CASE(config_flags%cu_physics)
CASE (KFSCHEME) CALL KFCPS(...) CASE (BMJSCHEME) CALL BMJCPS(...)
CASE DEFAULT
END SELECT cps_select
Match the package name in Registry
CASE (CHENSCHEME) CALL CHENCPS(...)
Put in
module_cu_chen.F

33. Physics_drive.int SUBROUTINE cumulus_driver(arg1, arg2, … &
newvar1, newvar2,… &
its,ite,jts,jte,kts,kte, &
ims,ime,jms,jme,kms,kme, &
ids,ide,jds,jde,kds,kde )
INTEGER, INTENT(IN) :: its,ite,jts,jte,kts,kte, &
ids,ide,jds,jde,kds,kde
REAL, INTENT(IN) :: arg1, arg2
REAL, INTENT(OUT), DIMENSION(kms:kme) :: &
newvar1,newvar2,….

34. . phy_prep chencps cumulus_driver solve_em calculate_phy_tend Might
update_phy_ten
phy_cu_ten
Might
need to
call MPP
DYNAMICS .

35. phys/module_physics_addtendc.F
Subroutine phy_cu_ten (… ) .
CASE(BMJSCHEME)
CASE (CHENSCHEME)
CALL add_a2a (rt_tendf, RTHCUTEN,… )
CALL add_a2c_u(ru_tendf,RUBLTEN,… )
CALL add_a2c_v(rv_tendf,RVBLTEN,… )
if (P_QS .ge. PARAM_FIRST_SCALAR) &
CALL add_a2a(moist_tendf(ims,kms,jms,P_QS),RQSCUTEN, .. &
ids,ide, jds, jde, kds, kde, &
ims, ime, jms, jme, kms, kme, &
its, ite, jts, jte, kts, kte )

36. module_cu_chen.F MODULE_CU_CHEN CONTRAINS!
SUBROUTINE cheninit (arg1, arg2, … ) .
ENDSUBROUTINE cheninit
SUBROUTINE chencps (arg3, arg4, … )
END SUBROUTINE chencps
END MODULE_CU_CHEN