IBM Research

IBM demonstrates Deep Thunder at AMS00 Comparison of RAMS results to those of other models Results from RAMS on the previous page showed predictions of weather for the southwestern United States on January 10-14, 2000.  A group at the Naval Postgraduate School runs another mesoscale model, MM5, at resolutions of 108, 36 and 12 km on an operational basis.  The forecasting domain that they used does not correspond exactly to what was used for AMS00.  However, the 12 km MM5 nest overlaps with most of the 16 km nest used for RAMS at AMS00, so these will be compared.  In addition, the MM5 runs employ 30 vertical levels vs. 31 used for RAMS.  Details of the MM5 forecasting environment and model configuration are available.  Unlike the RAMS runs, they are using NOGAPS (a global spectral model) instead of Eta (a synoptic scale model) results from NCEP for both initialization and boundary conditions for a 36 hour instead of 48-hour simulation, produced twice each day.  All of the results are posted as a set of static two-dimensional graphical images on the web. In an attempt to assess the differences between these two forecasting efforts, a qualitative comparison of RAMS results at 16 km resolution with MM5 results at 12 km resolution is discussed below for forecasts initialized at 12Z on 11 January 2000.  The comparison is limited at best for a number of reasons, including: Different domains are used in each forecast (resolution [grid spacing horizontally and vertically], extent [three-dimensional mesh size], centroid [center of the domain], and projection [cartographic coordinate system]) Weather variables in the plots from MM5 are expressed in different parameters and/or units. The only available information on MM5 results are static plots.  There is no access to actual data that could be compared.  In addition, only limited time steps common across the various forecasts were available.  (This was not a problem for RAMS since all of the data were available.) Simultaneous animation is limited as a comparison technique because each set of 3-hourly plots from a particular MM5 forecasts uses different scales for contours, color, etc. The following shows a simple comparison for wind forecasts.  Both show wind speed as colored contours and wind velocity as barbs.  There is similar structure between the two forecasts.  However, the wind results from RAMS are at the surface while those from MM5 are at an altitude of 24m.  The former shows a maximum of about 50 mph (22 m/sec) vs. 18 m/sec for RAMS.   lloydt@watson.ibm.com Last updated January 11, 2001