Psychrometric constant

The psychrometric constant, $γ =$ , ralates the thermometer bulb temperature readings^[1].

$\gamma =\frac{ \left( c_p \right)_{air} * P }{ \lambda_v * MW_{ratio} }$

γ =

psychrometric constant [kPa °C^-1],

P = atmospheric pressure [kPa],

λ v =

latent heat of water vaporization, 2.45 [MJ kg^-1],

c p =

specific heat of air at constant pressure, [MJ kg^-1 °C^-1],

M W r a t i o =

ratio molecular weight of water vapor/dry air = 0.622.