[Wrf-users] Rh at 2 meters

[Eric L. Altshuler]

Seshu,

Here is one way to calculate RH from q, T and p.
The units are assumed to be:

T: deg C (subtract 273.15 from T in deg K)
p: hPa (mb)
q: kg/kg (or g/g)

1. Calculate saturation vapor pressure from Bolton's formula:

es=6.112*exp(17.67*T/(T+243.5))

2. Calculate vapor pressure

e=q*p/(0.622+0.378*q)

3. Calculate RH

RH=100*e/es

For 2-m RH, use T2m for T, q2m for q, and ps (surface pressure) for p.

Best regards,
Eric L. Altshuler
Assistant Research Scientist
Center for Ocean-Land-Atmosphere Studies
Calverton, MD, USA
ela at cola.iges.org