Rapid Refresh (RAP) and High-Resolution Rapid Refresh (HRRR) Forum

Re: Mid-level data missing?

Posted By: John Brown
Date: 16-March-06 2344Z

In Response To: Re: Mid-level data missing? (Scott Dennstaedt)

Scott, I'll try to explain. The key is in the "hybrid" nature of the vertical coordinate. We assign each coordinate surface (from 1 to 50) a potential temperature (theta) value, starting at 224K (-49C) for the bottom level, and increasing at variable increments to 500K at the top (level number 50). Further, we don't let the coordinate surfaces go below ground, and we don't let them get too close to each other in the vertical. Given these 2 constraints, which we might call the subterrainian and the separation constraints, the RUC model seeks to put the coordinate surface as close to its assigned potential temperature as possible. The first level above the surface (assigned 224K) we keep always at 5 m above the ground surface, so it is always "terrain following". The second one, 232K (-41C) potential temperature, is also very cold, and almost always is colder than any potential temperature occurring in the model domain. Under these typical conditions, the code will put this coordinate surface as close to the lowest coordinate surface as the separation constraint allows (for these 2 levels, about 5mb over low elevations,

Messages In This Thread

Mid-level data missing? -- Scott Dennstaedt -- 9-March-06 2112Z

Re: Mid-level data missing? -- Stan Benjamin -- 13-March-06 2014Z

Re: Mid-level data missing? -- Scott Dennstaedt -- 16-March-06 2131Z

Re: Mid-level data missing? -- Bill Moninger -- 16-March-06 2158Z

Re: Mid-level data missing? -- John Brown -- 16-March-06 2344Z

Re: Mid-level data missing? -- John Brown -- 17-March-06 2010Z

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