Liquid–Ice Mass Partition in Tropical Maritime Convective Clouds

Abstract

he liquid?ice mass partitioning in tropical maritime convective clouds is studied using data collected by the National Center for Atmospheric Research C-130 research aircraft during the Ice in Clouds Experiment?Tropical project. The clouds investigated by the C-130 in this study generally contained weak to moderate updrafts. The liquid water content (LWC) is calculated using a combination of hot-wire and imaging probes. The total condensed water content (CWC) is measured by a counterflow virtual impactor. The ice water content (IWC) is calculated as CWC minus LWC. Taking into account potential significant measurement uncertainties, the liquid fraction [i.e., LWC/(LWC + IWC)] between 0° and ?15°C appears to decrease by a factor of about 3 in updrafts near (<500 m) cloud top and a factor of 2 in updrafts far below (>500 m) cloud top. The decrease in liquid fraction as a function of temperature is also correlated with cloud life cycle. In dissipating clouds, ice dominates in all temperature ranges. A comparison between this study and two parameterizations shows that at different geographic locations the liquid fraction in convective clouds differs. Because of the sampling bias and the limitations of instruments, more measurements, especially with more advanced instruments, are needed in the future.