Shapes, sizes and light scattering properties of ice crystals in cirrus and a persistent contrail during SUCCESS

Abstract

A persistent contrail in the shape of a racetrack was generated by the NASA DC-8 research aircraft during the SUCCESS project. The contrail was visible on GOES imagery for six hours. Microphysical measurements collected by the DC-8 show that after 40 min the core of the contrail contained mostly small (1 to 20 μm) ice particles in concentrations >1000 L-1, with larger (>300 μm) ice crystals in concentrations <10-6L-1. In contrast to the core, the contrail periphery contained about an order of magnitude less ice particles in the 1→20 μm range and about three orders of magntidue more ice particles >300 μm. The larger ice crystals in the periphery were mostly columns and bullet rosettes, similar to habits of larger ice crystals found in ambient cirrus in the area. Measurements suggest that the shape of phase functions of randomly-oriented columns and rosettes are mostly featureless. The measured phase functions are closest in shape to those predicted by ray-tracing theory for random-fractal and spatial-dendrite ice crystals.