Atmospheric IR propagation

Abstract The state-of-the-art of IR atmospheric propagation modelling — important to both scientific and practical applications of IR radiation—is reviewed, based mainly on experimental work performed at the FfO. The main improvements of transmission models rely on the results of measurements, analysis and modelling of aerosol and other atmospheric particle size distributions (0.15 μm ⪷ dia ⪷ 12 mm) over land and sea, performed in the context of long-range transmission experiments and lidar probings. Remaining problem areas will be identified and discussed, e.g. continuum absorption and fog window. The modelling of turbulence-induced fluctuations of amplitude and phase is of increasing interest as related to IR atmospheric windows and relevant laser lines. Recent experimental results on phase fluctuations are discussed, especially in relation to attempts to derive a better modelling of atmospheric microturbulence ( C n ).