Examination of the observed synoptic scale cirrus cloud environment: The December 3-6 FIRE cirrus case study

Recently, Sassen provided evidence for supercooled water droplets in cirrus uncinus cell heads at temperatures between 40 and -50 C. Chemistry related to volcanic aerosol of stratospheric origin was evoked as an explanation for this phenomenon. Sassen speculated that injections of sulfuric acid droplets into the upper troposphere were accomplished by tropopause folds associated with subtropical jet streams. He also postulated global climatic perturbations due to the effect of these cirrus microphysical perturbations on radiative fluxes. Using data processing and objective analysis techniques described by Mace and Ackerman, the synoptic scale environment was examined for evidence of tropopause folds that may have served as a source mechanism of stratospheric aerosol in the upper troposphere.