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wrf_eth

Calculates equivalent potential temperature from WRF model output.

Prototype

```	function wrf_eth (
qv  : numeric,
T   : numeric,
P   : numeric
)

return_val [dimsizes(qv)] :  float or double
```

Arguments

qv

Water vapor mixing ratio in [kg/kg]. An array with the same dimensionality as P.

T

Temperature in [K]. An array with the same dimensionality as P. This variable can be calculated by wrf_tk.

P

WRF: Full pressure (perturbation + base state pressure; Pa). The rightmost dimensions are bottom_top x south_north x west_east.

Non-WRF: Pressure (Pa).

Return value

Equivalent potential temperature (K). An array of the same size as qv. The type will be double if any of the input is double, and float otherwise.

Description

This function computes equivalent potential temperature (in K). The return variable will contain two attributes:

return_val@description = "Equivalent Potential Temperature"
return_val@units = "K"
This returns essentially identical value(s) as NCL's (6.5.0) pot_temp_equiv_tlcl function.

See the full list of WRF functions.

Examples

Note: for WRF variable names and their definitions, you can easily check them by using "ncl_filedump":

```  ncl_filedump wrfout_d01_2000-01-24_12:00:00.nc
```

Example 1

```   nc_file = addfile("wrfout_d01_2000-01-24_12:00:00.nc","r")
T  = nc_file->T
P  = nc_file->P
PB = nc_file->PB
qv = nc_file->QVAPOR

T  = T + 300.        ; potential temperature in K.
P  = P + PB          ; full pressure in Pa.
tk = wrf_tk( P , T ) ; temperature in K.

eth = wrf_eth ( qv, tk, P )
```
You can see some other example scripts and their resultant images at:
http://www2.mmm.ucar.edu/wrf/OnLineTutorial/Graphics/NCL/