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# wetbulb

Compute wetbulb temperature. Available in version 6.4.0 and later.

## Prototype

```	function wetbulb (
p    : numeric,
tc   : numeric,
tdc  : numeric
)

return_val [dimsizes(p)] :  numeric
```

## Arguments

p

A scalar or multi-dimensional array of pressures [hPa/mb].

tc

A scalar or multi-dimensional array of temperatures [C]. Must conform to p.

tdc

A scalar or multi-dimensional array of dew point temperatures [C]. Must conform to p.

## Return value

The returned wet bulb value(s) will have the same shape and size as p. It will be type double if any of the input arguments is type double; otherwise the values will by type float.

## Description

This function returns the wet-bulb temperature given the temperature [t; degC], dew point [td; degC] and pressure p [hPa]. See p.13 in Stipanuk (1973), for a description of the technique.

```
Source:
Thomas W. Schlatter and Donald V. Baker:
PROFS Program Office, NOAA Environmental Research Laboratories, Boulder, Colorado.

Reference:
Stipanuk, G.S., (1973) original version.
Algorithms for generating a skew-t, log p diagram
and computing selected meteorological quantities.
Atmospheric sciences laboratory
U.S. Army Electronics Command
White Sands Missile Range, New Mexico 88002
http://www.dtic.mil/dtic/tr/fulltext/u2/769739.pdf

f90 verion of code:
http://www.caps.ou.edu/ARPS/arpsbrowser/arps5.0Beta8browser/html_code/arps/thermolib3d.f90.html

```

## Examples

Example 1: Compute wet bulb temperature. Source Wallace & Hobbs (1977); page 106.

```   p   = 1000                   ; hPa, mb
tc  =   15                   ; C
tdc =    4                   ; C

twb = wetbulb(p, tc, tdc)    ; ===> 9.3C

Example 2:  Compute wet bulb temperature.

p   = (/1000, 975  , 850   /)                   ; hPa, mb
tc  = (/40  , 30   , 20   /)                    ; C
tdc = (/27.6, 26.17, 14.37/)                    ; C

twb = wetbulb(p, tc, tdc)

print(sprintf("%6.1f",p)+sprintf("%6.1f",t)+sprintf("%8.2",td)+sprintf("%8.2f",twb))

The (edited) output is:
P       T      TD     TWB
(0)	1000.0   40.0   27.60   30.45
(1)	 975.0   30.0   26.17   27.20
(2)	 850.0   20.0   14.37   16.45

Example 3

Given temperature (C), relative humidity (%) and pressure (hPa), compute wet bulb temperature.
The dew point function (dewtemp_trh) requires degrees K while the wetbulb function requires degrees C.
The values returned from an
interactive wet bulb calculator have been added for comparison.

p   = (/1000, 975, 850/)                  ; hPa
tc  = (/40, 30, 20/)                      ; C
rh  = (/50, 80, 70/)                      ; %

tk0 = 273.15                              ; compute dew point; compute to K
tdc = dewtemp_trh((tc+tk0), rh) - tk0   ; C->K then K->C

twb = wetbulb(p, tc, tdc)

print(sprintf("%6.1f", p)+ sprintf("%6.1f",tc) \
+ sprintf("%7.2f",tdc)+sprintf("%7.0",rh) \
+ sprintf("%8.2f",twb))

The (edited) output is:
P       T      TD    RH    TWB     EZC
(0)	1000.0   40.0   27.60   50   30.45   30.43
(1)	 975.0   30.0   26.17   80   27.20   27.11
(2)	 850.0   20.0   14.37   70   16.45   16.27

Example 4

Let t (C), td (C) and p (hPa)
be scalar or one/two/three/four-dimensional: (1), (ntim), (ntim,ncol), (ntim,nlat,mlon),
(ntim,klev,nlat,mlon). Then, the following will return an array of similar dimensionality
containing the wet bulb temperatures.

twb = wetbulb(p,t,td)

```