Utah ADAS

The Utah ADAS is based on the Oklahoma ARPS (Advanced Regional Prediction System) Data Analysis System, developed by the Center for Analysis and Prediction of Storms (CAPS) at the University of Oklahoma. This project is being carried out by the NOAA Cooperative Institute for Regional Prediction (CIRP) at the University of Utah. The goal is to obtain real-time mesoscale analyses at high temporal and spatial resolution over the complex terrain of the western United States. The implementation of the Utah ADAS is intended to assist local forecasting by the National Weather Service (NWS) and State Agencies.

Description of the Utah ADAS:

Summer 2002- 3D Analysis is not being run

ADAS is a 3-dimensional mesoscale analysis system. The Utah ADAS is currently being run on a 220 km square domain centered near the SLC NWSFO, with 1 km horizontal resolution. The grid is stretched in the vertical, varying from 9 m at the surface to about 600 m at the domain top. There are 33 vertical levels, with a height-based, terrain-following coordinate. The domain was selected so that it includes the WSR-88D radar at Promontory Point. The terrain data are mapped onto the ADAS grid using a multi-pass Barnes analysis and exhibit elevation changes from about 1200 m to 3100 m (msl) over the domain. The analysis program interpolates local observations onto the grid using an iterative interpolation scheme, combining the observed data with a large scale background field. The analyses are currently being run in real time at one hour intervals.
The ADAS analysis system also includes a complex cloud analysis package, developed at CAPS. The cloud analysis is initialized using a 3-dimensional fractional cloud cover field derived from the ADAS relative humidity. The cloud field is then modified using a Barnes analysis of visible and infrared satellite data and radar reflectivity.

The ADAS Surface Analysis:

The ADAS surface analysis is run using 4 vertical levels spaced at 5 meter intervals. The coordinate is terrain-following but is not stretched in the vertical. The grid points at the upper and lower bounds of the domain allow for implementation of the vertical boundary conditions; while the model physical top lies at 5 m above the terrain, model output occurs at the second scalar level, about 2.5 m above ground. The benefit of running a surface-only analysis is that the analysis can be run over a much larger domain while retaining high horizontal resolution, and the resulting mesoscale detail, in the analyses. In addition, the integration time of the ADAS surface analyses is significantly faster than a fully 3-dimensional analysis due to the reduction in vertical levels used. The drawback of this approach is that the surface analysis is not coupled to the full three-dimensional structure of the atmosphere.

The surface analysis is currently run over the Western United States at 2km and 10 km resolution. This domain is similar to the area contained within the Western Region of the National Weather Service. The 2 km analysis is run hourly while the 10 km analysis is generated every 15 minutes. The surface analysis has also been configured to run at 1km resolution over northern Utah.

  • The surface analyses use the RUC2 analyses as the initial background field, with local data provided by the MesoWest database.

    Analysis Cycle

  • Not running furing Summer 20021km 3-dimensional analyses over northern Utah are computed valid at the beginning of each hour.
  • 1km surface analyses over northern Utah and 10 km surface analyses over the western U.S. are computed at 00, 15, 30 and 45 minutes past each hour.
  • 2km surface analyses over the Western U. S. are run hourly.
  • Data (see types below) are collected up to 30 minutes past the valid time.
  • The 1 km 3-D analysis over the Wasatch Front begins at 37 minutes past the hour and is typically done by the beginning of the next hour. Graphics typically become available soon after that time.
  • The 10 km surface analysis is completed every 15 minutes to be consistent with the 15 minute cycle of MesoWest. The analyses are typically processed, graphics generated, and netCDF file delivered to NWS Offices in the NWS Western Region by about 40 minutes past the valid time. The 1 km surface analysis over northern Utah is completed on similar time scales. The 2 km western U.S. analysis is slower and finishes typically about an hour after the valid time.

    Analysis Modifications:

    Data Used in the 3-Dimensonal Analyses:

    Bratseth Interpolation Scheme:

    Other ADAS Features:

    Future Goals:

    References:

    Lazarus, S., C. Ciliberti, J. Horel, K. Brewster, 2002: Near-real time applications of a mesoscale analysis system to complex terrain. Wea. Forecasting. In press.
    Horel, J. D., C. M. Ciliberti, and S. M. Lazarus, 2001: Data assimilation over the western United States Preprints, 5th Symposium on Integrated Observing Systems, Albuquerque, New Mexico, Amer. Met. Soc., Jan. 14-19.
    Ciliberti, C. M., J. D. Horel, and S. M. Lazarus, 2000:Sensitivity Experiments with a High Resolution Data Assimilation SchemePreprints, 9th Conference on Mountain Meteorology, Aspen, Colorado, Aug. 7-11.
    Ciliberti, C. M., S. M. Lazarus, and J. D. Horel, 1999:An analysis of a cold frontal passage over complex terrain in northwest Utah. Preprints, 8th Conference on Mesoscale Processes, AMS.
    Lazarus, S. M., C. M. Ciliberti, and J. D. Horel, 1998: Application of a local analysis system in highly variable terrain. Preprints, 16th Conference on Weather and Forecasting , AMS.

    Acknowledgements:

    The ARPS Data Analysis System is made available by the Center for Analysis and Prediction of Storms at the University of Oklahoma. The people who have contributed to this project are Keith Brewster of CAPS, who has provided extensive technical support, and John Horel, Carol Ciliberti, and Steven Lazarus of CIRP at the University of Utah.