# relhum

Calculates relative humidity given temperature, mixing ratio, and pressure.

## Synopsis

```    function relhum(
t  : float,
w  : float,
p  : float
)

```

## Arguments

t
Temperature (K) (any dimensionality)
w
Mixing ratio (kg/kg) (same dimensions as t)
p
pressure (Pa) (same dimensions as p)

## Description

relhum returns a float array (of the same dimensionality as its input arrays) where each value represents the relative humidity given the temperature, mixing ratio, and pressure. The input arrays can be of any dimensionality as long as they are all the same dimensionality as each other.

## Example

```begin
p  =(/ 1008.,  \
1000.,950.,900.,850.,800.,750.,700.,650.,600., \
550.,500.,450.,400.,350.,300.,250.,200., \
175.,150.,125.,100., 80., 70., 60., 50., \
40., 30., 25., 20. /)
t  =(/  29.3,  \
28.1,23.5,20.9,18.4,15.9,13.1,10.1, 6.7, 3.1,   \
-0.5,-4.5,-9.0,-14.8,-21.5,-29.7,-40.0,-52.4,   \
-59.2,-66.5,-74.1,-78.5,-76.0,-71.6,-66.7,-61.3, \
-56.3,-51.7,-50.7,-47.5 /)
q  =(/  20.38, \
19.03,16.14,13.71,11.56,9.80,8.33,6.75,6.06,5.07, \
3.88, 3.29, 2.39, 1.70,1.00,0.60,0.20,0.00,0.00, \
0.00, 0.00, 0.00, 0.00,0.00,0.00,0.00,0.00,0.00, \
0.00, 0.00 /)

nlvl = dimsizes(p)
print (nlvl)

zsfc = 17.0
q    =  q*0.001
tk   = t+273.15
tkv  = tk*(1.+q*0.61)
tcv  =  tkv-273.15

zh   = hydro (p*100.,tkv,zsfc)

rhccm= relhum (tk, q, p*100. )

expp = 2.7182
eps = 0.62197

do n=0,nlvl-1
ev = q(n)*p(n)/(eps+q(n))
es = 6.112*expp^(17.67*tcv(n)/(243.5+tcv(n)))
rh =  (ev/es)*100.       ; in [%]; avoid 0
print ("HYDRO: "+n+" "+p(n)+" "+zh(n) \
+" "+q(n)+" "+tcv(n)\
+" rhccm="+rhccm(n) \
+" rh="   +rh)
end do
end

```

### Reference Manual Control Panel

\$Revision: 1.5 \$ \$Date: 1999/02/04 20:13:28 \$