NCAR Strategic Priority 4: Community Modeling
Highlight: Developmental Testbed Center (DTC)
The Developmental Testbed Center (DTC) is a national facility created in 2003 to facilitate the interaction of the operational and research communities in accelerating the improvement of Numerical Weather Prediction (NWP) for the U.S. The DTC effort at NCAR includes:
- A program for testing and evaluating various WRF model configurations so that the operational community can plan for changes and upgrades to the operational models and the research community has access to the latest NWP systems for testing and research.
- A visitor program that invites members from the operational and research communities to participate in the testing and evaluation of WRF.
- A user support system that provides documentation, tutorials, and helpdesk capabilities to aid users in both the research and operational communities in accessing and using WRF codes.
FY2007 Accomplishments:
3-h total precipitation (shaded), mean sea level pressure, and 1000-500 mb thickness fields for 60-h forecasts valid at 12 UTC on 3 May 2006. Right panel shows the ARW forecast and left panel shows the NMM forecast. Both WRF configurations used NAM initial and lateral boundary conditions and the same suite of physics parameterizations. For this particular forecast cycle, the ARW and NMM forecasts show rather different evolutions of the cyclone for this extended lead time.
WRF Testing and Evaluation: The current WRF Software Framework (WSF) supports two dynamic solvers: the Advanced Research WRF (ARW) developed by NCAR/MMM, and the Nonhydrostatic Mesoscale Model (NMM) developed by NCEP. In light of the results from the DTC’s 2006 Core Test, NOAA requested the DTC undertake an extended Core Test to determine whether the small differences in forecast skill between the two dynamic cores for 24 hour lead time also pertain to longer lead times (i.e., 60 hours). Preparations for this intensive testing of the NMM and ARW were completed near the end of FY07 and the actual runs are currently underway. In addition to extending the forecasts out to 60 hours, the DTC will be performing a platform comparison to test whether forecast skill is dependent on the computing platform used to generate the forecasts.
WRF Code Management: Based on extensive discussions between DTC staff, WRF developers, and the panel for the DTC Technical Review held in September 2007, the concept of a WRF Reference Code maintained by the DTC has evolved to a concept of WRF Reference Configurations. The configuration concept is much better suited to the current status of the WRF Code Repository and will likely also extend to how the DTC handles supporting the Operational Code or rather Operational Configurations to the user community.
WRF Tutorials The DTC conducted a WRF-NMM Tutorial in February 2007 and then joined efforts with MMM to conduct the first joint WRF Tutorial in July 2007 covering both the NMM and ARW dynamic cores. These tutorials include lectures on the pre-processor, model, and post-processing tools, as well as practical sessions that allow the participants to gain hands-on experience building and running each component of the end-to-end system. The tutorial participants once again represented a broad cross-section of both the national and international community.
DTC Verification System: During FY07, the DTC undertook the critical task of assembling a state-of-the-art verification toolkit, the Model Evaluation Tools (MET). This work is highlighted in a separate section of this RAL Annual Report.
DTC Visitor Program: The DTC released an “Announcement of Opportunity” for its 2007-2008 Visitor Program in March 2007. The DTC received 27 proposals and 10 of these proposals were selected for funding. These projects address much needed work in the areas of physics parameterizations, ensembles, verification techniques, and idealized capability for the NMM dynamic core.
FY2008 Plans:
WRF Testing and Evaluation: The DTC will complete the runs for its extended Core Test, analyze the results, and provide a report summarizing the results. This testing activity will likely lead to the first designations of Reference Configurations. The DTC will also undertake planning and execution of another Core Test comparing the forecast skill of the two dynamic cores for higher resolution forecasts (e.g., grid spacing on the order of 1 km). And finally, the DTC is planning to add data assimilation to its end-to-end system for testing and evaluation.
WRF Reference Code Management: The DTC will continue to develop the concept of Reference and Operational Configurations by putting together a written document describing the process for designating these configurations, the information and support that will be provided for these configurations, and how decisions will be made with respect to retiring configurations.
WRF Tutorials: Bi-annual WRF Tutorials are planned for FY08 (i.e., winter and summer offerings). The winter tutorial will cover basically the same material covered during summer 2007, whereas the summer 2008 tutorial will likely be extended from one week to two weeks in length to accommodate a wider range of information.
DTC Verification System: During FY08, the DTC plans to offer the first official release of MET to the community. Work will continue to extend the capabilities of MET to include a broader spectrum of verification capabilities, development of an online tutorial, and inclusion of MET in the WRF Tutorial in July 2008. Members of the verification community will also be invited to join DTC staff for a workshop to be held in spring 2008 to discuss new capabilities for MET and the development of a verification system in which MET could reside.
DTC Visitor Program: Another "Announcement of Opportunity" is expected to be issued in February 2008.
Data Assimilation Testbed Center
Established in August 2006, the Data Assimilation Testbed Center is collocated with the WRF Developmental Testbed Center within NCAR/RAL’s Joint Numerical Testbed (JNT). The DATC provides data assimilation resources and expertise to the NCAR and external research communities.
FY2007 Accomplishments
In its first year, the DATC has performed detailed assessments of data assimilation capabilities in a number of testbeds:
36hr WRF forecast verification against Antarctic sondes: Conventional observations only (red), conventional plus COSMIC (green), and retuned conventional plus COSMIC (blue).
Testing the Impact of COSMIC in Antarctica
Using data from the Antarctic Mesoscale Prediction System (AMPS) project, the DATC has performed a month-long evaluation of the impact of COSMIC local refractivity observations on Antarctic weather forecasts. The WRF-ARW model and WRF-Var were cycled continuously through the month of October 2006 (start of the Antarctic field season) and forecasts were integrated out to 72hrs four times a day using conventional observations with and without COSMIC data assimilated. The study found a significant positive impact of COSMIC refractivity assimilation on wind forecasts and tropospheric temperature and surface pressure. One negative result appears to be a degradation of stratospheric temperature forecasts, potentially due to excess gravity wave activity at the highest levels of the model and/or an overly simplistic representation of ozone in WRF. This study provided a rational and scientific basis for the operational implementation of COSMIC data in AMPS and also indicated areas of the WRF model that require further attention. Results from AMPS WRF-Var work were presented at the 2007 WRF Workshop and at the 2nd Antarctic Meteorological Observation, Modeling, and Forecasting Workshop in Rome, Italy, in June 2007.
24hr forecast verification (against all available conventional observations) for a) U-Wind, b) V-wind, c) Temperature, and d) Specific humidity. No data assimilation (red), update-cycling (blue), and full-cycling (green) experiments are shown.
Testing WRF-ARW cycling with WRF-Var in AFWA’s S. W. Asia Theater
To prepare for the Air Force Weather Agency’s anticipated worldwide regional implementation of WRF-ARW and WRF-Var, the DATC has established an AFWA testbed using global observations. Initial studies are focused on optimal data assimilation/forecast configurations on a South-West Asia regional domain. Currently, the data assimilation is performed every six hours, with the cycle being broken every twelve hours to blend back to NCEP’s global forecast system. The possibility of full-cycling (i.e. continuously cycling WRF-Var and WRF-ARW without reverting back to the global model data) has been tested in DATC in 2007. Figure 2 compares the 24hr forecast skill of update-cycling, full-cycling, and no data assimilation (i.e. WRF-ARW run from interpolated GFS analyses). Clearly, both cycling permutations produce superior forecasts to those run without regional data assimilation, with update-cycling producing the most accurate forecasts. These results provide a benchmark for further full-cycling experiments to be performed later in 2007 to assess the impact of AMSU and AIRS radiances, COSMIC, and tuned error covariance.
FY2008 Plans
In 2008, the DATC will continue detailed testing of data assimilation capabilities in a variety of applications. The Antarctic, Korean, and Taiwanese WRF NWPs testbeds will be supplemented by the first reanalysis testbed, a 10-year Arctic system reanalysis based on a 10-year (2000-2010) period and the WRF-ARW enhanced with polar physics.
The DATC will also begin to test and support the JCSDA’s GSI algorithm in 2008, initially to NCAR colleagues and visitors. This effort is part of the larger plan to work with the JCSDA (including NASA, the Navy, NOAA, and AFWA) in developing next-generation assimilation algorithms suitable for both research and operational communities.
Land Surface Modeling
RAL scientists work to understand, through theoretical and observational studies, the complex interactions (biophysical, hydrological, and bio-geochemical) between the land-surface and the atmosphere at micro- and mesoscales. The ultimate goal is to integrate such knowledge into numerical mesoscale weather prediction and regional climate models to improve prediction of the impacts of land-surface processes on regional weather, climate, and hydrology. Land surface modeling efforts were funded in FY07 by NSF, the Air Force Weather Agency (AFWA), NOAA, NASA, DTRA, and the CFD Research Corporation.
FY2007 Accomplishments:
(Top) The coupled Noah/urban canopy model (UCM) in the community mesoscale WRF model. (Bottom) Application of the WRF/Noah/Urban coupled modeling system over Salt Lake City and surrounding complex.
As part of a major collaborative effort among NCAR, NECP, NASA/GSFC, AFWA and several university groups, RAL scientists supported the development of the Unified Noah land surface model (LSM) for the numerical weather prediction community and its implementation in the Weather Research and Forecast (WRF) model. To meet the need for accurate weather prediction over urban areas (especially important for the air-quality modeling community), an advanced single-layer urban canopy model was coupled to Noah (Fig. 1) and released in WRF V2.2. In a new project started in FY07, supported by the Defense Threat Reduction Agency (DTRA), we are working towards improving the land-use data set in the DTRA Joint Effects Model/Hazard Prediction and Assessment Capability (JEM/HPAC) system and in WRF.
The team also applied the Noah-urban modeling system, with 1-km grid spacing, in WRF, where the resulting forecast fields were used to drive a CFD-model-based transport and dispersion model for a case study during the Joint Urban 2003 field experiment conducted in Okalahoma City. Verification results indicate that the use of the WRF forecasts by the quasi-steady CFD-Urban model has resulted in a significant improvement (by four or five times) in the accuracy of transport and dispersion calculations, compared with input from a single sounding instead of WRF.
Although the important role of soil moisture in the development of deep-convection has been recognized, it remains the most difficult variable to obtain because there is no routine high-resolution observation of soil moisture at the continental scale. Thus, a High-Resolution Land Data Assimilation System (HRLDAS) has been developed to support the WRF/Noah coupled land surface modeling system and ATEC range forecasts. It uses observed hourly precipitation, solar radiation derived from satellite, and analyzed surface wind and temperature to force a land-surface model to simulate the evolution of soil moisture. In this system, the NCEP/NOAA hourly 4-km rainfall analysis, based on NEXRAD and rain-gauge observations, is used so that errors in soil moisture caused by precipitation and radiation bias in coupled modeling systems could be avoided. Long-term HRLDAS simulations were conducted over the U.S. Southern Great Plains region to support RAL land-atmospheric interaction studies for IHOP 2002.
FY2008 Plans:
- Use MODIS vegetation products and photosynthesis-based model (GEM) to improve the representation of vegetation transpiration processes in the Noah land surface model.
- Implement a multi-layer urban canopy model in the WRF/Noah coupled modeling system and improve the representation of building morphology.
- Using Kalman filter technique to assimilate the profile of soil moisture and temperature in the high-resolution land data assimilation system.
- Investigate the coupling between surface hydrology, biogenic emission and vegetation processes using the Noah, GEM, canopy model, and MEGAN models.