Performance of RUC13 and WRFRUC13 forecasts for the AIRS-2 11 November 2003 icing case
Current plans call for the RUC to be replaced in late 2007 by a new "Rapid Refresh" system now under development at the Forecast Systems Lab. Two major changes from the present RUC will be 1) expansion of the domain to cover all of North America and adjacent ocean areas, and 2) use of some version of WRF as the forecast model in place of the current hydrostatic RUC model. We are now testing a candidate version of WRF (the "Advanced Research WRF) at FSL and expect to be running this test version with the Thompson et al microphysics later this year. This version, known as the WRFRUC13, uses RUC initial and lateral boundary conditions on a horizontal grid and domain identical to the RUC13. Its performance is being evaluated against the RUC13 on a continuing basis. One of the systematic differences we note is that the WRFRUC produces substantially more grid-scale precipitation than does the RUC, a difference we expect will continue when we run the 2 models with identical microphysics.
At the conference we will discuss results of the 11 November 2003 AIRS-2 case from both RUC13 and our pre-Rapid Refresh test version of WRF, with emphasis on the mixed-phase microphysics as it relates to icing. Comparisons will be made with observations as well as between comparable runs using the 2 models. Although the boundary layer and radiation physics differ between the 2 models, this does afford an opportunity to see how WRF (at least the ARW) and RUC compare at identical horizontal and similar vertical resolutions, and with identical initial and lateral boundary conditions.