Growth of ice crystals in a precipitating contrail

This study examines how jet aircraft contrails develop precipitation trails, using data collected on 12 May, 1996 during SUCCESS. The DC-8 sampled the precontrail conditions, produced a contrail largely in clear air at -52°C, and sampled the contrail and developing trails for over an hour. The environment was highly ice-supersaturated, reaching nearly water saturation in some locations. Inside the contrail core, almost all ice particles remained small (~1 to 10 μm) due to high crystal concentrations (~10¹ to 10² cm^-3) which reduced the vapor density to saturation. Mixing of moist environmental air and vapor-depleted contrail air produced localized regions of supersaturation along the contrail periphery, where crystals grew to several hundred microns at about 0.1 μm s^-1. These particles could then fall from the contrail into the vapor-rich, undepleted, supersaturated environment below. As heavier crystals left the contrail, others moved into the regions of ice supersaturation. Precipitation trails developed as this process continued over time.