Using the well-known approximation to calculate the dew point temperature from the actual temperature and the relative humidity, it is very easy to write a small script that can do this calculation for us.

I choosed Python to do this job. Feel free to use this script for your own purposes:

import sys
import numpy as np
# approximation valid for
# 0 degC < T < 60 degC
# 1% < RH < 100%
# 0 degC < Td < 50 degC
# constants
a = 17.271
b = 237.7 # degC
# sys.argv[0] is program name
T=float(sys.argv[1])
RH=float(sys.argv[2])
def dewpoint_approximation(T,RH):
Td = (b * gamma(T,RH)) / (a - gamma(T,RH))
return Td
def gamma(T,RH):
g = (a * T / (b + T)) + np.log(RH/100.0)
return g
Td = dewpoint_approximation(T,RH)
print 'T, RH',T,RH
print 'Td=',Td |

import sys
import numpy as np
# approximation valid for
# 0 degC < T < 60 degC
# 1% < RH < 100%
# 0 degC < Td < 50 degC
# constants
a = 17.271
b = 237.7 # degC
# sys.argv[0] is program name
T=float(sys.argv[1])
RH=float(sys.argv[2])
def dewpoint_approximation(T,RH):
Td = (b * gamma(T,RH)) / (a - gamma(T,RH))
return Td
def gamma(T,RH):
g = (a * T / (b + T)) + np.log(RH/100.0)
return g
Td = dewpoint_approximation(T,RH)
print 'T, RH',T,RH
print 'Td=',Td

The script expects two input parameters. First the temperature (in °C) and second the relative humidity (in %).