Emissivity is the ratio of the power emitted by an object to the power that would be emitted by a perfect black body having the same temperature as the object. The emissivity is assumed to be an integral over all wavelengths, unless a coordinate of radiation_wavelength or radiation_frequency is included to specify either the wavelength or frequency. In an atmosphere model, stratiform cloud is that produced by large-scale convergence (not the convection schemes). "longwave" means longwave radiation.