Codes Employed

The components of the end-to-end forecast system used in the WRF Rapid Refresh Core Test included:

    • Standard Initialization (SI) (Note: Each dynamic core has its own        approach to processing the input data and thus differences        between the initial and lateral boundary conditions, as well as the        static fields (e.g. terrain height) are possible.)

    • WRF model (Note: The WRF code used in this test does not        correspond to a public release, but is based on WRF v2.0 with        significant changes and enhancements.)

    • WRF Post Processor (WPP) (v2.0)

    • NCEP Verification System

    • NCAR Command Language (NCL) for graphics generation

    • Statistical programming language, R, to compute aggregations        and confidence intervals

Domain Configuration

    • CONUS domain with roughly 13-km grid spacing (selected such        that it fits within the RUC13 domain)
Click thumbnail for larger image.
Figure above shows the boundaries of the computational domain used for the ARW (dashed line), the NMM (dotted line) and the post-processed domain (solid line), which corresponds to the RUC13 domain.

    • Grid dimensions:
       • NMM: 280 x 435 gridpoints, for a total of 121,800 horizontal        gridpoints
       • ARW: 400 x 304 gridpoints, for a total of 121,600 horizontal        gridpoints
       • Post-processed: 451 x 337 gridpoints, for a total of 151,987        horizontal gridpoints

    • 50 vertical levels - (Note: An exact match in vertical levels is not        possible because the ARW uses a sigma-pressure vertical        coordinate, while the NMM uses a hybrid system, with sigma-        pressure levels below 300 hPa and isobaric levels aloft)

    • Projections:
       • NMM: Rotated Latitude-Longitude projection
       • ARW: Lambert-Conformal map projection

Sample Namelists

     ARW configuration:
        SI namelist
        namelist.input (for Physics Suite 1 (ph1))
        namelist.input (for Physics Suite 2 (ph2))

     NMM configuration:
         SI namelist
         namelist.input (for Physics Suite 1 (ph1))
         namelist.input (for Physics Suite 2 (ph2))

The end-to-end system for this test did not include a data assimilation component.

Initial and Boundary Conditions

    • Initial conditions (ICs): 13-km Rapid Update Cycle (RUC13)

    • Lateral Boundary Conditions (LBCs): North American        Mesoscale Model (NAM212) (Note: For the retrospective period        used, the forecast component of the NAM was the Eta model)

    • Sea Surface Temperature (SST) Initialization: NCEPs daily,        real-time SST product

Cases Run

The ARW and NMM dynamic cores were used to forecast 252 cases divided into the four seasons. The runs were initialized every 12 h, therefore alternating 00 and 12 hr cycles, and run out to 24 hours.

The table below lists the forecast cases that were not verified due to the reasons described in the table.

Missing Verification:

Verification

The NCEP Verification System is comprised of:
    • Surface and Upper Air Verification System (grid-to-point        comparison)
    • Quantitative Precipitation Forecast (QPF) Verification
       System (grid-to-grid comparison)

These packages provide model verification partial sums (aggregated by geographical region using the mean) that were used to compute objective model verification statistics. Confidence intervals (CIs), at the 99% level, were applied to each of the variables using the appropriate statistical method.

Objective verification statistics generated included:
    • Root Mean Squared Error (RMSE) and Mean Error (Bias) for:
        • Surface Temperature (2 m), Relative Humidity (2 m) and            Winds (10 m)
        • Upper Air Temperature, Relative Humidity and Winds

    • Equitable Threat Score (ETS) and Frequency Bias (FBias) for:
        • 3-hr and 24-hr Precipiation Accumulation intervals

Verification statistics were only computed for cases that ran to completion for both configurations. This set up allowed for a pair-wise difference technique, which takes advantage of the fact that both configurations faced the same forecast challenge for all cases, to be employed in the determination of statistically significant differences between the two configurations. The CIs on the pair-wise differences between statistics for the two configurations objectively determines whether the differences are statistically significant (SS).

Verification results were computed for select spatial aggregations, including the entire CONUS (G164), CONUS-West (G165), and CONUS-East (G166) domains (shown here).