AMPS uses WRF ARW version 3.7.1, with polar modifications to the released code to better treat the polar environment.
For recent changes, see History.
WRF uses a terrain-following vertical coordinate, defined according to
η = (Ph - Pht) / μ
|Ph||is the hydrostatic pressure|
|Pht||is the constant hydrostatic pressure at the model top|
|Phs||is the surface pressure|
|μ||= Phs - Pht|
η has a value of 1.0 at the surface and 0.0 at the model top.
WRF uses a staggered vertical grid on an η (eta) coordinate, with half-η levels defined halfway between full-η levels.
The AMPS configuration features 61 full-η levels and 60 half-η levels, specified as follows:
The AMPS configuration features five two-way interactive grids as follows (see Maps):
Terrain fields are generated from the RAMP2 data set.
Sea Ice fields are obtained from the Near Real-Time SSM/I EASE-Grid Daily Global Ice Concentration and Snow Extent data set.
SST Data are obtained from daily NCEP Global 0.5-degree analyses.
Model initial and boundary conditions are derived from NCEP 0.25-degree GFS model output (6-hourly intervals out to 120 hours).
WRFVAR 3D Variational data assimilation is used.
Hybrid option introduced 2016-05-25/12, using an ensemble of approximately 14 members in conjunction with the usual BE Stats.
Options (Physics parameterizations, mostly):
For details on these options below, see the Chapter 5 of the WRF ARW Users' Guide.
RRTMG Longwave radiation scheme (ra_lw_physics=4), updated every 15 minutes (radt=15).
Goddard shortwave radiation scheme (ra_sw_physics=2), updated every 15 minutes (radt=15).
Mellor-Yamada-Janjic (Eta) TKE scheme (bl_pbl_physics=2), updated every time step (bldt=0).
Monin-Obukhov (Janjic Eta) scheme (sf_sfclay_physics=2),
Unified Noah LSM (sf_surface_physics=2),
WSM 5-class scheme (mp_physics=4)
Kain-Fritsch (new Eta) parameterization (cu_physics=1) on 30- and 10-km grids, updated every time step (cudt=0)
No cumulus parameterizations (cu_physics=0) on 3.3- and 1.1-km grids
A fractional sea-ice implementation is used, in which the surface-layer scheme is called twice: first for completely frozen conditions, then for completely open water conditions. The results of these two calls are then weighted by the sea-ice fraction to determine surface fluxes and other terms.
Upper Boundary Condition:
Model top at 10 mb. Vertical velocity damping is applied (w_damping=1) in the top 7.5 km (zdamp = 7500.)
e-mail: Kevin Manning