Calculates dewpoint temperature in [C] from ARW WRF model output.
function wrf_td ( P : numeric, qv : numeric ) return_val [dimsizes(P)] : float or double
Full pressure (perturbation + base state pressure). The rightmost dimensions are bottom_top x south_north x west_east. Units must be [Pa].qv
Water vapor mixing ratio in [kg/kg]. An array with the same dimensionality as P.
Dewpoint temperature in [C]. The multi-dimensional array has the same size as P. The type will be double if P or qv are double, and float otherwise.
This function returns dewpoint temperature in [C]. It also makes sure there are no negative values in qv by setting them all to 0.
The return variable will contain two attributes:
return_val@description = "Dewpoint Temperature"
return_val@units = "C"
As of version 5.1.0, the return variable will contain the same named dimensions (if any) of qv. Otherwise, the rightmost two dimensions will be named "south_north" and "west_east".
Questions on this function should be sent to firstname.lastname@example.org.
See the full list of WRF functions.
Note: for WRF variable names and their definitions, you can easily check them by using "ncl_filedump":
QVAPOR = nc_file->QVAPOR(time,:,:,:) P = nc_file->P(time,:,:,:) PB = nc_file->PB(time,:,:,:) p = P + PB td = wrf_td( p , QVAPOR )Example 2
The function wrf_user_getvar (available in the $NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl script) can also be used to calculate many diagnostics in one step.
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl" load "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl" a = addfile("wrfout_d01_2000-01-24_12:00:00.nc","r") time = 1 td = wrf_user_getvar(a,"td",time) ; calculate tdYou can see some other example scripts and their resultant images at: