WRF-RR Vertical Level Sensitivity Test

WRF-RR Vertical Level Sensitivity Test

  • Code
  • Domain
  • Model
  • Initialization
  • Cases
  • Verification

Codes Employed

The components of the end-to-end forecast system used in the WRFRR-VL Test included:

    • WRF Preprocessing System (WPS) (v3.0)

    • WRF-ARW model (v3.0)

    • WRF Post Processor (WPP) (v3.0)

    • NCEP Verification System

    • NCAR Command Language (NCL) for graphics generation

    • Statistical programming language, R, to compute 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.

    • 400 x 304 gridpoints, for a total of 121,600 horizontal gridpoints

    • 50 vertical levels (51 sigma entries) - The two configurations are        identical except for the for the distribution of the nine lowest sigma        levels.

    • Lambert-Conformal map projection

Sample Namelists


     namelist.input for the high vertical resolution at low levels (ARW1)

     namelist.input for the default vertical resolution (ARW2)

Physics Suite

Microphysics: Thompson
Radiation (LW/SW): RRTM/Dudhia
Surface Layer: Janic
Land Surface: RUC
PBL: Mellor-Yamada-Janjic
Convection: Grell-Devenyi Ensemble

Other run-time settings

    • Long timestep = 72 s; Acoustic timestep = 18 s

    • Calls to the boundary layer, microphysics and cumulus        parameterization were made every time step

    • Calls to radiation were made every 30 minutes

    • Sample namelist.input for ARW1 and ARW2

While the end-to-end system for this test did not include a data assimilation component, the RUC13 cloud fields were included in the initial conditions, so the runs were not truly cold start forecasts in the sense of starting with no clouds; there was, however, no attempt to create an initial divergent wind component that is consistent with the initial clouds.

Initial and Boundary Conditions

    • Initial conditions (ICs): Rapid Update Cycle (RUC13) model

    • 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

    • Forecast Dates: 25 March - 25 April 2006

    • Initializations: 00 and 12 UTC every day

    • Forecast Length: 24 hours; output files generated every 3        hours

The following cases did not successfully complete the entire end-to-end process due to the reason stated:
    • 20060329 12 UTC - missing RFC analysis
    • 20060402 00 UTC - corrupt RUC input
    • 20060413 00 UTC - missing NAM input
    • 20060417 12 UTC - missing RUC input
    • 20060418 00 UTC - missing RUC input
    • 20060423 00 UTC - missing RFC analysis
    • 20060423 12 UTC - missing RFC analysis and RUC prepbufr


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

From these, model verification partial sums (aggregated by geographical region using the mean) were generated and objective model verification statistics were then computed using the statistical programming language, R. Confidence intervals (CIs), at the 99% level, were applied to each of the variables using the appropriate statistical method.

Objective verification statistics generated included:
    • Bias-corrected Root Mean Square Error (BCRMSE) and Mean
(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

Since verification statistics were only computed for cases that ran to completion for both configurations of the model, pair-wise differences between the verification statistics of the two configurations are computed. 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.

Descriptions of the verification metrics computed can be found in Appendix B of the WRF-RR Vertical Levels Final Report.