Spatial Heterogeneity and Inhomogeneity of Cirrus Microphysical Properties on Kilometer Spatial Scales

Abstract Previous studies reporting the spatial inhomogeneity and heterogeneity of cirrus cloud properties have primarily been case studies derived from relatively small data sets. This study evaluates the spatial heterogeneity and inhomogeneity of cirrus bulk microphysical properties using ∼60 hr of in situ measurements from eight field campaigns. The spatial heterogeneity of ice concentration (ice water content) increases with decreasing ice concentration (ice water content), revealing more tenuous cirrus are more spatially heterogenous. Cirrus clouds often contain heavily skewed distributions of ice concentrations, which also possess high spatial heterogeneity. This is primarily due to the absence of small ice crystals (diameter < ∼50 μm) within localized regions of the clouds. These regions contain lower ozone concentrations and broader distributions of relative humidity with respect to ice. The greater variation of relative humidity suggests enhanced temperature perturbations resulting in greater frequencies of subsaturated samples, which preferentially sublimate small ice (e.g., via the kelvin effect).