Rapid Refresh (RAP) and High-Resolution Rapid Refresh (HRRR) Forum
Re: Mid-level data missing?
Posted By: John Brown In Response To: Re: Mid-level data missing? (Scott Dennstaedt)
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
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,
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