Assessment of clear and cloudy sky parameterizations for daily downwelling longwave radiation over different land surfaces in Florida, USA

Clear sky downwelling longwave radiation (R(1dc)) and cloudy sky downwelling longwave radiation (R(1d)) formulas were tested across eleven sites in Florida. The Brunt equation, using air vapor pressure and temperature measurements, provides the best R(1dc) estimates with a root mean square error of less than around 12 Wm(-2) across all sites. The Crawford and Duchon's cloudiness factor with Brunt equation is recommended for R(1d) calculations. This combined approach requires no local calibration and estimates R(1d) with a root mean square error of less than around 13 Wm(-2) and squared correlation coefficients that typically exceed 0.9. Citation: Choi, M., J. M. Jacobs, and W. P. Kustas (2008), Assessment of clear and cloudy sky parameterizations for daily downwelling longwave radiation over different land surfaces in Florida, USA, Geophys. Res. Lett., 35, L20402, doi: 10.1029/2008GL035731.