Ice Nucleation in Low-Temperature Aircraft Contrails During CRYSTAL-FACE

Upper tropospheric ice clouds and aircraft condensation trails (contrails) were studied by both remote sensing instruments on the NASA ER-2 high-altitude aircraft and in situ atmospheric sampling instruments on the NASA WB-57F aircraft as part of the NASA CRYSTAL-FACE mission. During the Southern survey flights of July 9 and July 26, 2002, over the Caribbean Sea, non-persistent and persistent visible contrails were produced by the WB-57F aircraft and imaged by the MODIS Airborne Simulator (MAS), flying at higher altitude on the ER-2. These contrails were located in the vicinity of the local tropopause, where ambient temperatures were very low (minus 74 to minus 78° C). A consistent relation was found between contrail lifetime and ambient humidity, as measured by the JPL Laser Hygrometer (JLH) using temperatures from the WB-57F Meteorological Measurement System (MMS). We will discuss contrail physical properties in relation to nearby cirrus clouds, sensitivities of different MAS channels to contrail properties, in situ measurements of humidity and particles, and model simulations of ice nucleation and growth, and contrail dispersal.