Quantitative Measurement of the Microphysical and Optical Properties of Cirrus clouds with Four Different in Situ Probes: Evidence of Small Ice Crystals

Abstract

Original microphysical and optical measurements were obtained in cirrus clouds on the Southern and Northern hemispheres during the INCA experiments using four independent techniques: (1) the Counterflow Virtual Impactor, (2) the PMS FSSP-300, (3) the PMS 2D-C and (4) the Polar Nephelometer probes. The combination of these four techniques provides a description of particles within a diameter range varying from a few micrometers (typically 3 μm) to 800 μm. Because of the presence of small ice crystals in cirrus clouds, it is particularly important to overcome the limited accuracy of the sensors used in the experiments for the cloud microphysical measurements. Representative examples of combined results suggest that the available measurements are reliable and can be used for the ongoing comparison between the results from the SH and NH campaigns. The results give the definite picture that the observations of numerous (5 to 10 cm^-3) small ice crystals in cirrus clouds are a relatively common microphysical feature.