On the Statistical Distribution of Total Water in Cirrus Clouds

Abstract

Distributions of total water in cirrus provide important information on cloud-scale variability. Observations of water variables in cirrus are sparse, limiting our ability to constrain factors controlling their evolution and lifetimes. We present and analyze aircraft measurements of tropical and extratropical cirrus total water statistics. We show that observed distributions are replicated by a parametric model that only requires knowledge of in-cloud temperatures. We parameterize the temporal decay of cloud ice content and distribution skewness forced by ice crystal sedimentation and find that ice water content decays at a much faster rate than skewness in the absence of cloud ice and skewness sources. The sensitivity of skewness to changes in ice water content is small. Our methodology and findings may prove useful for studies addressing statistical cloud schemes and cirrus life cycles.