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Objectives The primary focus of the Regional Analysis and Prediction Branch is research and development of the Rapid Update Cycle (RUC) and its development version, the Mesoscale Analysis and Prediction System (MAPS), which provide high-frequency, hourly analyses of conventional and new data sources over the contiguous United States and short-range numerical forecasts in support of aviation and severe storm forecasting and other mesoscale forecast users. The RUC runs operationally at the National Centers for Environmental Prediction (NCEP) at the highest frequency among its suite of operational models. In addition to developing and testing improvements to the RUC at FSL, another key focus of the branch has been the actual transfer of improvements made in MAPS at FSL to the RUC running at NCEP. During this past year, a related major ongoing task began in which FSL runs, in real time, a backup version of the RUC in a "hardened" computer environment to assure a high level of reliability. This task involves both the RAP Branch and FSL's Facility Division, along with NCEP and other areas of the National Weather Service (NWS). The RAP Branch works closely with NCEP in implementing these improvements to the RUC. A variety of model and assimilation development, verification, and observational data investigation activities are carried out under the RUC/MAPS focus. The RUC has a unique role within the NWS in that it is the only operational system that provides updated national-scale numerical analyses and forecasts more often than once every 6 hours. It was developed in response to the needs of the aviation community and other forecast users for high-frequency, mesoscale analyses and short-range forecasts covering the conterminous United States. It is a critical part of the NWS modernization program, and has become widely used in NWS Forecast Offices and other facilities. Evaluations of the RUC have clearly demonstrated its advantage in providing high-frequency, recently initialized forecasts based on the latest observations. The RUC is a key part of the Aviation Weather Program – commercial and general aviation are both critically dependent on accurate short-range forecasts. The RUC will continue to improve over the next several years, thus perpetuating the successful collaboration between FSL and NCEP. In collaboration with other government agencies and universities, scientists develop improved data assimilation and modeling methods for use in the RUC. New datasets are assimilated as they become available, so that all potentially useful observations can be incorporated to define the current atmospheric and surface conditions, thereby producing the most accurate forecast possible. The branch also interacts with other FSL staff in implementing optimal computing methods with RUC software, making the model as efficient as possible on modern computing platforms. Accomplishments Development of the 20-km RUC
Following the implementation of the 40-kilometer RUC-2 at NCEP in April 1998,
scientists in the RAP Branch have worked on development of a new version of
the
RUC planned for implementation at NCEP in late 2000 or early 2001. The higher
horizontal resolution of the new version takes advantage of the improved
computing capability at NCEP on its IBM SP computer. There are four key
aspects
to this new version: finer (20-kilometer) horizontal resolution (requiring
about
eight times the computations of the 40-kilometer version for the forecast
model),
an improved version of the RUC forecast model, assimilation of GOES-based
cloud-
top pressure to improve the initial RUC cloud fields for each forecast, and
use
of a three-dimensional variational analysis, replacing the current optimal
interpolation analysis. The 20-kilometer RUC Forecast Model – The 20-kilometer RUC forecast model has incorporated many improvements that, even without the change in horizontal resolution, result in better RUC forecasts. The key areas of improvement are:
The new version of the RUC model has been tested on a large number of cases, including the 3 May 1999 Oklahoma tornado case for which the predicted convective precipitation from the 40-km RUC was not particularly accurate. The convective precipitation for the 9–12 hour period valid at the time of the thunderstorm outbreak associated with the tornadoes is presented in Figure 2 (next page) for the 40-kilometer RUC forecast and for a 20-km run simulation with the new RUC model. A radar summary valid in the same period is shown for comparison. The improvement in the 20-kilometer RUC simulation is a result of three factors: the improved model, higher resolution, and the use of analyzed instead of forecast boundary conditions. In addition to these changes, the RUC forecast model software was rewritten with much greater modularity and also to use a new pre-processor for message passing (part of the Scalable Modeling System (SMS) development under FSL's Aviation Division). The message-passing preprocessor (PPP/SMS) allows the RUC model to continue to use local-memory parallel computers, but now with less intrusive compiler directives. The use of SMS in the RUC allowed, for instance, a very easy transition to NCEP's IBM SP local-memory computer. An Initial Cloud Analysis for the RUC Using Assimilation of GOES Cloud-top Pressure – An explicit mixed-phase cloud microphysics scheme was introduced into operations along with the 40-kilometer RUC in 1998. This scheme includes explicit prediction of mixing ratios for five hydrometeors, cloud water, cloud ice, rain, snow, and graupel. The initial fields for these variables for each hourly cycle in the current 40-kilometer RUC is currently taken from the previous 1-hour forecast without modification. Ongoing research over the last three years has led to development of an analysis technique that modifies these RUC cloud hydrometeor fields based on information from a GOES sounder-based cloud-top product produced by NESDIS. This technique includes both building of clouds if the 1-hour forecast had incorrectly indicated clear conditions and clearing of clouds if the forecast had incorrectly predicted clouds. The technique has been shown to improve short-range cloud-top forecasts consistently (Figure 3), especially in 1-hour and 3-hour forecasts, but even out to 12-hour forecasts, to reduce errors in relative humidity forecasts, and to improve precipitation forecasts. A Three-Dimensional Variational Analysis – The current operational 40-km RUC has performed relatively well using initial fields from an optimal interpolation (OI) analysis configured in its native hybrid isentropic/terrain-following coordinates. However, a three-dimensional variational (3DVAR) analysis approach has been under development for the RUC for a few years in order to allow initial or improved assimilation of remotely sensed observations (e.g., satellite and radar) and to reduce small-scale noise associated with the OI analysis. This technique will be introduced with the 20-kilometer RUC. It has been shown to produce wind and height forecasts of better quality than those initialized by a RUC OI analysis in parallel cycle tests at a 60-kilometer resolution.
Development of Improved Atmospheric/Land-Surface Coupled Model Capability and Production of Integrated Datasets for GEWEX/GCIP - FSL continues to participate in the multiyear Global Energy and Water Cycle Experiment (GEWEX) and its GEWEX Continental-scale Intercomparison Project (GCIP) by providing data from the RUC-2/MAPS model to the GCIP archive of gridded datasets. The goal of GCIP is improved understanding of the continental-scale hydrological cycle components, and ultimately, improved climate prediction capability. Ongoing improvements to all aspects of RUC/MAPS, but especially to its land-surface component, contribute toward this goal. RUC/MAPS fields from runs at FSL integrating various data sources on a high-frequency basis are being used, along with those from the Eta model and the Canadian Regional Finite Element model, to better understand the energy and water cycles over the United States and southern Canada. The continued improvement of the soil/vegetation model in RUC/MAPS contributes strongly to the accuracy of its estimates of critical hydrological fields for GCIP, including surface fluxes and soil moisture. FSL began applying the RUC in a regional climate simulation mode, taking advantage of work in previous years toward a more robust coupled atmospheric/land-surface model capability. Runs were made for the 2-month period of June-July 1993 constrained only by lateral boundary conditions from the NOAA/NCEP Reanalysis (2-month precipitation from one of the RUC experiments shown in Figure 4). Despite the climate application of GCIP, these same improvements are often quite important for improved short-range forecasts of surface temperature, clouds, and precipitation from the RUC needed by its operational users. Verification of the RUC/MAPS Forecasts - Daily monitoring and verification of the MAPS/RUC temperature, wind, humidity, precipitation, and cloud analyses and forecasts are continuing as part of an effort to detect coding problems and physical inconsistencies in the analysis scheme and forecast model.
Use of RUC Wind Forecasts for Estimated Wind Power Potential – The RUC/MAPS group started a project with the National Renewable Energy Laboratory for using wind forecasts from RUC to produce experimental forecasts of the potential for wind power generation. The high vertical resolution of the RUC near the surface and high accuracy of surface winds makes the RUC a good source of model guidance for this problem. Backup Capability for the Operational RUC from FSL – In the first half of 1999, NCEP asked FSL if it could provide a real-time backup capability for the operational RUC at NCEP. Such a capability with dedicated computer resources and operator support was developed by FSL's Forecast Research Division and Facility Division in coordination with NCEP and other parts of NWS, and was invoked after the fire in the NCEP computer facility. FSL continues to provide this real-time backup capability on an ongoing basis. The forecast model component of the RUC backup runs successfully on FSL's new supercomputer, Jet.
Transfer of the Operational RUC to NCEP's IBM SP Computer, New Output Variables – FSL worked successfully with scientists from NCEP to complete the transfer of the entire 40-kilometer RUC system to NCEP's IBM SP computer in 1999. The transfer of the RUC forecast model to the IBM SP computer was made much easier by the previous incorporation of Scalable Modeling System (SMS) software, allowing use of message passing between processors with distributed memory. Eight new diagnostic variables were also added to RUC output, including cloud top/base, visibility, surface wind gust potential, equilibrium level, and convective cloud-top potential. Other Accomplishments The following additional accomplishments were carried out in the Regional Analysis and Prediction Branch during Fiscal Year 1999. The MAPS/RUC Web Homepage – Continued enhancements were made to the MAPS/RUC homepage, including the addition of forecasts from the backup RUC running at FSL, new products such as precipitation type, visibility, and wind gust speed, and continuation of the popular RUC user forum (http://maps.fsl.noaa.gov/), which provides the latest news on the RUC and answer user questions. Observation Sensitivity Experiments Using RUC for NAOS – Experiments using the RUC with a 1-hour cycle and forecasts out to 36 hours every 12 hours were conducted for different observation mixes. Three different experiments were carried out for an 11-day test period as part of the multiagency North American Observation System experiment. Similar experiments have been carried out with NCEP's Eta and Aviation model by NCEP. Observation Sensitivity Experiments Using RUC to Examine Impact of GPS Precipitable Water Observations – In collaboration with the Demonstration Division, 60-km RUC parallel cycle experiments with and without assimilation of GPS precipitable water observations were carried out. With the availability of 55 stations starting in late 1999, a significant positive impact on short-range precipitation and relative humidity forecasts has been shown in these experiments. Participation in Development of the Weather Research and Forecast (WRF) Model System – The overall goal of the WRF model project is to develop a next- generation mesoscale forecast model and assimilation system that will advance both the understanding and prediction of important mesoscale weather, and promote closer ties between the research and operational forecasting communities. The model and associated system are being developed as a collaborative effort among NCAR, NCEP, FSL, the Center for the Analysis and Prediction of Storms (CAPS), and other research institutions, together with the participation of a number of university scientists. Because the project aims to improve the forecast accuracy of significant weather on horizontal scales of a few kilometers, the model will be nonhydrostatic. It is anticipated that this model will be a leading candidate to replace the present hydrostatic RUC model to serve the rapid updating function at NCEP. FSL has continued its work toward a significant option for the WRF forecast model, a version using a generalized vertical coordinate that can move during the model integration. This work is being done in collaboration with scientists from the University of Miami and NCAR. This option allows the use of a smoothed hybrid isentropic/sigma-z coordinate that retains the advantages of the RUC hybrid coordinate on scales of 20 km or greater, but also accommodates local perturbations such as convective clouds or breaking mountain waves with quasi-horizontal coordinates. Development of the Well-Posed Model – Work continues on the development of a well-posed fourth order accurate limited area model. As the final step in showing how to apply the Bounded Derivative Theory to atmospheric flows evolving on the adjective timescale anywhere on the globe, a manuscript has been submitted to the open literature which shows that slowly evolving equatorial motions at any length scale satisfy the same balance between the vertical velocity and heating as in the midlatitude mesoscale case (earlier publication). Thus, any gravity waves that are generated at the equator play only a minor role in the evolution of the associated storm; i.e., Bounded Derivative Initialization (BDI) can be applied to the initial data to ensure that the fast waves will be removed from the ensuing solution without significant impact on the storm. The research shows how the projection of equatorial data onto the normal modes of the adiabatic system is misleading as to the amount of energy in equatorial gravity waves. The inappropriate projection of the dominant component of the solution onto gravity waves by this method is the source of the confusion about the relative importance of latter waves. Current research (to be published soon) also shows how BDI can be applied to multiscale flows in a global model or in an open boundary limited area model anywhere on the globe. In addition, FSL is collaborating on a project to apply these initialization techniques to the Canadian global weather forecast model. Projections The Regional Analysis and Prediction Branch will continue to work with the National Centers for Environmental Prediction to improve the Rapid Update Cycle over the next several years. The primary near-term tasks follow: Complete Development of the 20-kilometer RUC – Final testing of all 20-kilometer RUC components will be completed at FSL. Transfer of the 20-kilometer RUC to NCEP's new IBM SP Computer – Testing of a 20-kilometer RUC at NCEP will occur in a parallel cycle. The implementation will take place after this parallel cycle testing when it can be scheduled with NCEP. This higher-resolution version is expected to improve RUC accuracy in many areas, but especially for cloud, precipitation, and surface forecasts. Development of a National-Scale Cloud Analysis – Development and real-time testing will continue for further improvements to the RUC national-scale cloud analysis, with the addition of radar and surface observations to satellite cloud- top data. Experiments will be carried out testing assimilation of a GOES imager-based multilevel cloud product. Refinement and Testing of Improved Physical Parameterizations for Soil/Vegetation Processes, Turbulence, Convective Clouds, and Cloud Microphysics – Some of this work will be done in collaboration with NCAR, since the RUC model uses some MM5 parameterizations. Also, some of these same parameterizations will be options for the WRF model. Development of the Three-Dimensional Variational Analysis – Development and real-time testing will continue on the 3DVAR analysis, both for incorporation into the RUC and toward the development of the WRF 3DVAR analysis. Testing of the Nonhydrostatic Generalized Vertical Coordinate Model – Testing of this model will continue, in collaboration with the University of Miami and NCAR, as part of FSL's contribution to the overall multiagency development of the Weather Research and Forecast model. Other Activities The following activities are also planned during Fiscal Year 2000. Preparation for Experimental RUC Forecasts for the PACJET Experiment in Fiscal Year 2001 – Work will begin for setting up a configuration for the RUC in a 20-kilometer domain over the western United States and eastern Pacific to be used in the multiagency PACJET experiment in Fiscal Year 2001. RUC cycles will run with and without special observations designed to improve mesoscale forecasts of winds and precipitation along the United States West Coast in winter storms. A 10-kilometer RUC model will run in a nest inside these domains, allowing improved prediction of orographic effects. Participation in GEWEX – Collaboration will continue on the GEWEX/GCIP program, including improvement of land surface processes in RUC/MAPS, particularly with new high-resolution land-use and soil datasets. The RUC regional climate simulation capability will be improved and exercised for seasonal and multiyear periods. Contribution of RUC 60-hour Forecasts to an NCEP Short-Range Ensemble Forecast – As part of an expansion to NCEP's Short-Range Ensemble Forecast (SREF) project, FSL will set up a version of the RUC model to run out to 60 hour on a 40-kilometer grid over the North American Eta domain. Development of the Well-Posed Model – Research will continue on the Well-Posed Model's Bounded Derivative Initialization applications.
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