A parametric radiative forcing model for cirrus and contrail cirrus

Abstract

rameterization to compute the instantaneous radiative ux changes induced by thin cirrus (including contrail cirrus) at top of the atmosphere. The method is part of a new contrail cirrus prediction tool CoCiP. The model is being prepared to interpret cirrus cover and radiative irradiance values derived from Meteosat data. CoCiP computes the shortwave and longwave radiative forcing for given outgoing longwave radiation (OLR) and re- ected solar radiation (RSR) irradiance values without contrails. This a priori information is taken from a numerical weather prediction model such as the forecast model of ECMWF. The parameterization contains several free model parameters which are determined by a least squares t to an extensive set of forward calculations performed with the radiative transfer package libRadtran. The approximate results and the libRadtran results correlate better than 98%. Further improvements appear to be feasible.