Funding to maintain WRF-NMM at the DTC has ended and support will no longer be provided. To download HWRF, please see: www.dtcenter.org/HurrWRF/users. To download WRF-ARW, please see: www2.mmm.ucar.edu/wrf/users . To download NEMS-NMMB, please see: www.dtcenter.org/nems_nmmb/users.To download UPP, please see: www.dtcenter.org/upp/users.

NMM Dynamical Solver

The WRF-NMM is a fully compressible, non-hydrostatic mesoscale model with a hydrostatic option (Janjic et al. 2001, Janjic 2003a,b). The model uses a terrain following hybrid sigma-pressure vertical coordinate. The grid staggering is the Arakawa E-grid. The same time step is used for all terms. The dynamics conserve a number of first and second order quantities including energy and enstrophy (Janjic 1984).

The WRF-NMM model code contains an initialization program (real_nmm.exe; see Chapter 4 of the WRF-NMM User's Guide) and a numerical integration program (wrf.exe; see Chapter 5 of the WRF-NMM User's Guide). The WRF-NMM model Version 3 supports a variety of capabilities. The key features include:

• Real-data simulations for applications ranging from meters to thousands of kilometers.
• Fully compressible, non-hydrostatic model with a hydrostatic (runtime) option (Janjic, 2003a).
• Hybrid (sigma-pressure) vertical coordinate.
• Arakawa E-grid.
• Forward-backward scheme for horizontally propagating fast waves, implicit scheme for vertically propagating sound waves, Adams-Bashforth Scheme for horizontal advection, and Crank-Nicholson scheme for vertical advection. The same time step is used for all terms.
• Conservation of a number of first and second order quantities, including energy and enstrophy (Janjic 1984).
• Full physics options for land-surface, planetary boundary layer, atmospheric and surface radiation, microphysics, and cumulus convection.
• One-way and two-way nesting with multiple nests and nest levels.

WRF-NMM Dynamics

Time stepping

Horizontally propagating fast-waves: Forward-backward scheme
Vertically propagating sound waves: Implicit scheme
Horizontal: Adams-Bashforth scheme
Vertical: Crank-Nicholson scheme
TKE, water species: Explicit, iterative, flux-corrected (called every two time steps).

Advection (space) for T, U, V

Horizontal: Energy and enstrophy conserving, quadratic conservative, second order
Vertical: Quadratic conservative, second order
TKE, Water species: Upstream, flux-corrected, positive definite, conservative

Diffusion

Diffusion in the WRF-NMM is categorized as lateral diffusion and vertical diffusion. The vertical diffusion in the PBL and in the free atmosphere is handled by the surface layer scheme and by the boundary layer parameterization scheme (Janjic 1996a, 1996b, 2002a, 2002b). The lateral diffusion is formulated following the Smagorinsky non-linear approach (Janjic 1990). The control parameter for the lateral diffusion is the square of Smagorinsky constant.

Divergence damping

The horizontal component of divergence is damped (Sadourny 1975). In addition, if applied, the technique for coupling the elementary subgrids of the E grid (Janjic 1979) damps the divergent part of flow.

Physics

Below is a summary of physics options that are well-tested for WRF-NMM and used operationally at NCEP:

&physics	Identifying Number	Physics options
mp_physics (max_dom)	5	Microphysics-Ferrier
ra_lw_physics	99	Long-wave radiation - GFDL (Fels-Schwarzkopf)
ra_sw_physics	99	Short-wave radiation - GFDL (Lacis-Hansen)
sf_sfclay_physics	2	Surface-layer- Janjic scheme
sf_surface_physics	2	Land-surface - Noah LSM
bl_pbl_physics	2	Boundary-layer - Mellor-Yamada-Janjic TKE
cu_physics	2	Cumulus - Betts-Miller-Janjic scheme
num_soil_layers	4	Number of soil layers in land surface model

Below is a summary of physics options that have been tested for the WRF-NMM and whether they run or fail:

Physics Options	Runs (option)	Fails (option)
Microphysics	WSM5 (4) Ferrier (5)* WSM6 (6) Thompson (8)	Lin (2) WSM3 (3)
Radiation (lw/sw)	GFDL/GFDL (99)* RRTM/Dudhia (1)	Goddard (2)
Sfc Layer/PBL	M-O/YSU (1) Janjic/MYJ (2)* GFS/GFS (3) QNSE (4) GFDL (88)
LSM	Unified Noah (2)* RUC (3) GFDL (88)
Cummulus	None (0) KF (1) BMJ (2)* GD (3) AS (4)*

* indcates well-tested for WRF-NMM

(For more details and references, see the Physics Options section in Chapter 5 of the WRF-NMM User's Guide.)

Inputs for WRF initialization

Real-data using WRF Preprocessing System (WPS) conversion from Grib files

I/O options

netCDF, most common. Works with all supported graphics.

Platforms it runs on

Below is a summary of platforms that are tested for WRF-NMM:

Vendor	Hardware	O.S.	Compiler
Cray	X1	UniCOS	vendor
Cray	AMD	Linux	PGI/PathScale
IBM	Power Series	AIX	vendor
SGI	IA64/Opteron	Linux	Intel
COTS*	IA32	Linux	Intel/PGI/gfortran/g95/PathScale
COTS*	IA64/Opteron	Linux	Intel/PGI/gfortran/PathScale
Mac	Power Series	Darwin	xlf/g95/PGI/Intel
Mac	Intel	Darwin	g95/PGI/Intel

*Commercial off the shelf systems.

(For more details and references, see Chapter 2 of the WRF-NMM User's Guide.)

Software Architecture

Hierarchical software architecture that insulates scientific code (Model Layer) from computer architecture (Driver Layer).

Multi-level parallelism supporting shared-memory (OpenMP), distributed-memory (MPI), and hybrid share/distributed modes of execution.

Active data registry: defines and manages model state fields, I/O, nesting, configuration, and numerous other aspects of WRF through a single file, called the Registry.

ESMF Time Management, including exact arithmetic for fractional time steps (no drift).

Software architecture documentation, both on-line (web based browsing tools) and in-line are available.