Pacific Northwest Mesoscale Model Weather Forecasts: Information

For a description of the MM5-NAM forecasts click here

For a description of our older, experimental WRF forecasts click here

For a description of our older, real-time MM5 forecasts click here

General Information: The Department of Atmospheric Sciences at the University of Washington is now running the Advanced Research WRF (WRF-ARW) core of the Weather Research and Forecasting Model (WRF) version 3.7.1 (WRF-ARW v3.7.1). Forecasts are run twice a day in order to produce high resolution meteorological guidance for the Pacific Northwest. This effort, supported by a consortium of local, state, and federal agencies, has several goals:

• To provide high resolution meteorological fields for air quality applications, weather forecasting, and other needs.
• To test the viability of local numerical weather forecasting completed on relatively low-cost workstations.
• To provide a large number of mesoscale model forecasts to determine model strengths, weaknesses, and biases.
• To improve mesoscale model physics and data assimilation approaches.
• To test the potential of directly coupling an atmospheric forecast model to air quality and hydrological numerical models.

Change Log: For the latest information on our setup, please consult the Change Log for Pacific Northwest WRF/MM5 Numerical Forecasts

Model Configuration: The WRF numerical forecasts currently feature an outer grid of 36 km horizontal resolution that covers much of western North America and the northeastern Pacific; a nested grid of 12 km resolution that covers Washington, Oregon, Idaho, Utah, much of Montana and Nevada, southern British Columbia, and northern California; and an inner 4 km resolution grid encompassing all of Washington, Oregon, and Idaho plus the western third of Montana and the extreme northern sections of California, Nevada, and Utah, and the western third of Wyoming. A high-resolution 4/3-km domain is also run which covers Washington, Oregon, the western portion of Idaho, and the extreme southern 40-50 km of British Columbia. The regions covered by each domain, showing topography and land use categories are shown in these plots:

New version Compatible with WRF		Old version from TERRAIN
Terrain	Land Use	Terrain	Land Use
36-km terrain	36-km land use	36-km terrain	36-km land use
12 km terrain	12 km land use	12 km terrain	12 km land use
4 km terrain	4 km land use	4 km terrain	4 km land use
1.33 km terrain	1.33 km land use	1.33 km terrain	1.33 km land use

A land use category color key is included in the links above, you may view it alone here. And, the USGS landuse color key is here.

A detailed description of the domain boundaries can be found in the actual geogrid.exe namelist.wps file or in the MM5 terrain.deck. Detailed land use information for each domain was derived from the 1-km MODIS digital database.

The model utilizes 38 vertical full-eta levels see below, and is run in non-hydrostatic mode in order to limit pressure gradient force errors over the complex terrain. An upper-radiative boundary condition is used to allow gravity waves to radiate through the model top without being reflected. The following table describes the phyics options we are currently using:

Phyics and Other Options:

Physics	Comments
Radiation	RRTMG shortwave and longwave radiation schemes.
Thompson Microphysics	Includes graupel.
Grell-Freitas ensemble scheme for Cumulus Convection	Begain using Grell-Freitas with the 2015110312 run. Prior to that, the Simplified Arakawa-Schubert scheme was used from 2012122100-2015110300. The old Kain-Fritsch scheme was used through 2012122012, but non-physical lines of accumulated precipitation (see here) forced us to drop it.
YSU PBL	Yonsei University scheme (new MRF). Non-local-K scheme with explicit entrainment layer and parabolic K profile in unstable mixed layer. NOTE: the module_bl_ysu.F from version 3.0 of the WRF was backported into the version 2.2.1 WRF that was run up to and including the 2009010900 case.
Noah-MP Land Surface Model	Beginning with the 2015012900 case, we have switched to the Noah-MP which uses multiple options for key land-atmosphere interactions. As noted in the documentaion: Noah-MP contains a separate vegetation canopy defined by a canopy top and bottom with leaf physical and radiometric properties used in a two-stream canopy radiation transfer scheme that includes shading effects. Noah-MP contains a multi-layer snow pack with liquid water storage and melt/refreeze capability and a snow-interception model describing loading/unloading, melt/refreeze, and sublimation of the canopy-intercepted snow. Multiple options are available for surface water infiltration and runoff, and groundwater transfer and storage including water table depth to an unconfined aquifer. Horizontal and vertical vegetation density can be prescribed or predicted using prognostic photosynthesis and dynamic vegetation models that allocate carbon to vegetation (leaf, stem, wood and root) and soil carbon pools (fast and slow).
aer_opt = 2 (summer months only)	Running from the 2018081600 run to the 2018100312 forecast, we used the aer_opt = 2 settings, adding the predicted 2-d aerosol optical depth (AOD) at 550 nm (AOD5502D in WRF) and the predicted 2-d aerosol Angstrom exponent (ANGEXP2D in WRF) from NASA's GEOS-5 system. WRF's aerosol single-scattering albedo (AERSSA2D) and aerosol asymmetry factor (AERASY2D) are set to the recommended fixed values of 0.85 and 0.9, respectively. See the latest 36/12/4 km namelist.input and 4/3 km namelist.input for a complete list of the aerosol settings.

Here are the exact namelist.input files that are used to run the model: 36/12/4 km namelist.input and 4/3 km namelist.input (these two links are updated with each model run.). For more information on any of these options, see the WRF model chapter of the WRF User's Guide.

1. MM5-NAM: 4-processor Intex Xeon Linux box.
2. WRF-GFS: Eight 20-processor Intel Xeon cluster running Debian Linux .

 October 11, 2012 and after Eta levels:
        1.000,  0.995,  0.990,  0.9841, 0.9772, 
	0.9702, 0.9620, 0.9525, 0.9414, 0.9284, 
	0.9134, 0.8960, 0.8759, 0.8527, 0.8260, 
	0.7955, 0.7608, 0.7218, 0.6785, 0.6309, 
	0.5785, 0.5213, 0.4594, 0.3953, 0.3360, 
	0.2832, 0.2363, 0.1951, 0.1595, 0.1291, 
	0.1031, 0.0806, 0.0612, 0.0449, 0.0312, 
	0.0194, 0.0091, 0.000

 pre-October 11, 2012 Eta levels:
         1.00, 0.995*, 0.99, 0.985*, 0.98, 0.97, 0.96, 0.95*, 
         0.94, 0.93*, 0.92, 0.91*, 0.90,
         0.88, 0.86, 0.83, 0.80, 0.77, 0.74, 0.71,
         0.68, 0.64, 0.60, 0.56, 0.52, 0.48, 0.44, 0.40, 
         0.36, 0.32, 0.28, 0.24, 0.20, 0.16, 0.12, 0.08, 0.04, 0.
	 * = added 7/9/2001