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

Re: Questions Regarding Hybrid Level

Posted By: John M. Brown
Date: 18-January-13 0228Z

In Response To: Questions Regarding Hybrid Level (David Daniel)

David, The RAP uses as the forecast model a configuration of the Weather Research and Forecast (WRF) model. The vertical coordinate in this model is the sigma coordinate, not the hybrid sigma - pressure coordinate that is described in the second link in your post. The sigma coordinate is similar to the hybrid sigma - pressure coordinate, except that it does not become purely pressure until the top of the model (in the case of the RAP, this is 10 hPa, or about 30km in altitude). You can find out details about the WRF model at http://www.mmm.ucar.edu/wrf/users/docs/arw_v3.pdf. See section 2.1 of this document for an explanation of the vertical coordinate. If you are specifically interested in the Planetary Boundary Layer (PBL), there is a variable for the height (or depth) of the PBL, which is quite variable in space and time. The name of this variable is HPBL (in meters), given in the first link in your post. It is down toward the bottom of the list in this link. If this information is insufficient to put you on the right track toward the answer to your questions, I suggest you send me an email directly.

Messages In This Thread

Questions Regarding Hybrid Level -- David Daniel -- 18-January-13 0134Z

Re: Questions Regarding Hybrid Level -- John M. Brown -- 18-January-13 0228Z

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