Hemispheric comparison of cirrus cloud evolution using in situ measurements in HIAPER Pole-to-Pole Observations

Abstract

Cirrus clouds' radiative forcing is highly sensitive to their microphysical properties and evolution. However, there are very limited data sets with both microscale resolution and global coverage to provide a hemispheric comparison of cirrus cloud microphysical properties and their evolution. Here we use in situ aircraft observations on the ~200 m scale from 87°N to 67°S over North America and the central Pacific Ocean to analyze the hemispheric differences in the evolution of cirrus clouds' horizontal segments—ice supersaturated regions (ISSRs) and ice crystal regions (ICRs). In contrast to previous in situ observations, we show that the clear-sky ice supersaturation frequency, resulting microphysical parameters (ice crystal size and concentration), and relative timescale of the life cycle of ISSRs and ICRs are similar between the Northern and Southern Hemispheres. More studies on hemispheric ice nuclei distributions and dynamical conditions are needed to help explain these observations.