def humidexC(t_C, rh):
"""Calculate the humidex
Reference (look under heading "Humidex"):
http://climate.weather.gc.ca/climate_normals/normals_documentation_e.html?docID=1981
t_C - temperature in degree Celsius
rh - relative humidity [0-100]
Examples:
>>> print "%.2f" % humidexC(30.0, 80.0)
43.64
>>> print "%.2f" % humidexC(30.0, 20.0)
30.00
>>> print "%.2f" % humidexC(0, 80.0)
0.00
>>> print humidexC(30.0, None)
None
"""
try:
dp_C = dewpointC(t_C, rh)
dp_K = CtoK(dp_C)
e = 6.11 * math.exp(5417.7530 * (1 / 273.16 - 1 / dp_K))
h = 0.5555 * (e - 10.0)
except (ValueError, OverflowError, TypeError):
return None
return t_C + h if h > 0 else t_C
def _etterm(elev_meter, t_C):
"""Calculate elevation/temperature term for sea level calculation."""
t_K = CtoK(t_C)
return math.exp(-elev_meter / (t_K * 29.263))
