Figure 1. Predicted spectra for fogs comprising molecular absorption and particle loss computed from standard models; corresponding to visibilities of 50(…), 10(---) and 150(___) m. Spectra observed in the atmosphere corresponding to the models. The standard deviation in the measured spectra is 3 dB km-1. In such fogs the liquid drops are all small compared with the wavelengths and show Rayleigh region behavior in which attenuation varies monotonically. Nether this component nor equilibrium dimers can accounr for the observed additional structure between monomer lines.