Ice Water Path–Optical Depth Relationships for Cirrus and Deep Stratiform Ice Cloud Layers

Abstract

Abstract Particle size distribution (PSD) and particle shape information collected during Lagrangian spiral descents and balloon ascents through 13 midlatitude and 6 tropical ice clouds are analyzed to investigate the relationship between cloud optical depth in visible wavelengths (τυ) and the ice water path (IWP). Although this sample size is small, it is far larger than the number of samples used in earlier studies and has the added benefit that it contains data from the top to the bottom of cloud layers, averaging 3 km in geometrical thickness. Furthermore, the observed particle shape and habit information are used directly in the investigation, rather than assuming that the habits are one of a number of pristine types. These observations apply to midlatitude clouds in the temperature range from −65° to −20°C, with τυ between 0.5 and 7, and estimated radar reflectivities primarily in the range from −20 to 5 dBZe (at a frequency of 35 GHz), with some observations extending down to −45 dBZe. The tropical...