What is plg?

[Chris Hayes]

Jeffrey Duda wrote:
> Hello,
> I am using RUC model output for analyses and I have two variables that
> confuse me.
>
> Here is output from "q ctlinfo":
>
> capesfc  0  157  ** surface Convective Avail. Pot. Energy [J/kg]
> capeplg  0  157  ** Convective Avail. Pot. Energy [J/kg]
>
> cinsfc  0  156  ** surface Convective inhibition [J/kg]
> cinplg  0  156  ** Convective inhibition [J/kg]
>
> For each of these pairs of thermodynamic variables, what is the
> "...plg" one?  Is it some sort of mixed layer value?  Please help explain.
>
For what it's worth; the variable explaining file
http://dss.ucar.edu/datasets/ds090.2/docs/all-vars-subgroups says:

 plg   layer btwn two pres levs rel to sfc


hth