Liquid fraction in stratiform mixed-phase clouds from in situ observations

Liquid fractions in mixed-phase clouds have been analysed using aircraft measurements taken in mid- and high latitude stratiform clouds. The liquid fraction generally increases with temperature but has a minimum at about -15 degreesC, where the maximum ice crystal growth based on vapour deposition would be expected. The mean liquid fraction also depends on total water content. This suggests that segregation of cloud phase based on a simple linear relationship of phase fraction (ice or liquid) with temperature, as is used in some climate models, may be unrealistic. Parametrizations of mean liquid fraction in terms of temperature and total water content, and in terms of temperature alone, have been developed based on data averaged at 10 s resolution (1 km). These parametrizations agree reasonably well with the observations.