WRF Model:

Physics Implementation

OUTLINE

Physics schemesThree_level StructureRules for WRF physicsWRF Physics FeaturesWRF LanguageWhat you might need to do

Shu-hua Chen

Physics Schemes

Physical Process Available

Microphysics Kessler, Lin et al. , Ncloud3, Nloud5

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 5-layer soil temperature

Physics Interface Design

User friendly •• Simple

Different dynamics cores •Three-level structure =>

Solver

Physics_driverSELECT CASE (CHOICE) CASE ( NOPHY ) CASE ( SCHEME1 ) CALL XXX CASE ( SCHEME2 ) CALL YYY CASE DEFAULTEND SELECT

Individual physics scheme ( XXX )

Three-level Structure

WRF … solve_rk ADV TENDENCIES

phy_init

ADVANCE VARS

…

INIT

.

.

.

microphysics_driver

Radiation_driver

Cumulus_driver

pbl_driver

phy_prep

moist_physics_prep

phy_prep & moist_physics_prep

• Decouple variables

• Convert variables from C grid

to A grid

Domain size: ids, ide, jds, jde, kds, kde

Memory size: ims, ime, jms, jme, kms, kme

Tile size: its, ite, jts, jte, kts, kte

Three Sets of Dimensions

Tile size (its,kts,jds)

halo

halo

haloh

alo

(ims,ime)

tile

tile

tile

tile

tile

tile

(its,ite)

Coding rules

Vectorized code preferred

( might depend on which physics component )

Rules for WRF Physics

Naming rules

One scheme one module

a) Replace continuation characters in the 6th column with f90 continuation `&‘ at end of previous line

1. F90

b)Replace the 1st column `C` for comment with `!`

2. No common block

3. Use “ implicit none ”

5. Variable dimensions and do loops

Coding Rules

4. Use “ intent ”

xxx = individual scheme

ex, module_cu_kf.F

Naming Rules

module_yy_xxx.F (module)

yy = ra is for radiation bl is for PBL cu is for cumulus mp is for microphysics.

YY = ra is for radiation bl is for PBL cu is for cumulus

Naming Rules

RXXYYTEN (tendencies)

XX = variable (th, u, v, qv, qc, … )

ex, RTHBLTEN

• Unified global constatnts

(module_model_constants.F)

WRF Physics Features

• Unified some calculations

(saturation mixing ratio)

• Vertical index (kms is at bottom)

• kme = kte + 1 (physics)

kme = kte (dynamics)

WRF Language

• 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 )

. . .

namelist.input

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,