The code in ARWpost/src/module_interp.f90, line 229 and lin 271:
data_out(i,j,k) = tlev * (1000./plev)**gamma
I guess the 1000 should be 100000. As the unit of VAR "plev" is Pa (not hPa).
Unless this error is removed, the output of theta in Z level (unit: km) below ground( extrapolate = .true. in namelist.ARWpost ) is not good.