SPARTICUS and MACPEX Cirrus Particle Sizes and Habits as a Function of Temperature and Synoptic Cirrus Type

Extensive in-situ observations of midlatitude Cirrus obtained during the Small Particles in Cirrus (SPARTICUS) project and Midlatitude Airborne Cirrus Properties Experiment (MACPEX) project have been compared with numerical simulations of Cirrus microphysical properties, and the synoptically-forced cirrus cases have been stratified into three temperature regimes (205-215K, 215-225K and 225-235K). Cloud particle habits classified using high image resolution Cloud Particle Imager (CPI) observations and particle size distributions obtained using 2D-S observations are summarized for each of these three temperature regimes. Surprisingly, the temperature regime does not correlate closely with the particle habits observed, although changes in the observed particle size distributions do correlate with temperature. The particle habit types observed correlate much better with the thermodynamic 'atmospheric state', resulting in classifications such as Ridge Crest, Frontal Cirrus and Subtropical Jet Cirrus. Also surprisingly, the column and plate habit types occurred less frequently for all temperature regimes than rosettes, budding rosettes and aggregates. Particle size is generally larger at warmer temperatures, and appears to be both due to greater depositional growth and aggregation as particles sediment through the cloud.