A scattering phase function for ice cloud: Tests of applicability using aircraft and satellite multi-angle multi-wavelength radiance measurements of cirrus

A parametrization of the Henyey-Greenstein scattering phase function is presented for application to aircraft and satellite remote sensing of cirrus-cloud bulk and microphysical properties at non-absorbing and absorbing wavelengths. The phase function is based initially around a non-absorbing laboratory-measured phase function between scattering angles of 30 degrees and 180 degrees, although at scattering angles greater than 95 degrees the phase function is made constant with scattering angle. This 'analytic' phase function has an asymmetry parameter value of 0.80 at non-absorbing wavelengths. This analytic phase function is tested using aircraft-based transmission radiance measurements at the wavelengths of 0.55 mum, 0.87 mum, 1.6 mum and 3.7 mum between scattering angles of 10 degrees and 120 degrees, and satellite retrievals of cirrus-cloud spherical albedo at the wavelength of 0.67 mum between scattering angles of 60 degrees and 180 degrees. The analytic phase function reproduces both aircraft and satellite measurements well, and is shown to be a distinct improvement over single-crystal model phase functions representing both small and large crystals in terms of angular scattering pattern and retrieved optical thickness.