A new long-wave formula for estimating downward clear-sky radiation at the surface

A new formula is proposed for estimating the long-wave radiation from clear skies. The formula depends on screen-level air temperature and water vapour pressure. The formula has been extensively tested using long-wave measurements covering a large range of environmental temperatures (-40 to +40 degrees C), and by using radiosonde profiles and an accurate radiative-transfer model (Lowtran-7). It is shown that the new formula out-performs five other widely used formulas.