Estimating downward clear sky long‐wave irradiance at the surface from screen temperature and precipitable water

Abstract This paper presents two parametrizations of the downward clear sky long‐wave irradiance at the surface of the earth in terms of screen temperature and precipitable water. The first parametrization is based on a simple physical model, while the second is an extension of Swinbank's model by the addition of a term involving precipitable water. The parametrizations achieve standard deviations of approximately 5 W m −2 when compared with detailed radiative‐transfer calculations for temperature and moisture profiles in the TOVS Initial Guess Retrieval data set. Both models are more accurate than Swinbank's model, and other published models that are expressed in terms of the screen temperature and surface vapour pressure.