An Analysis of the Tropical Cyclone Cirrus Canopy Using HS3 and TCI Observations

Tropical cyclones (TCs) are characterized by a horizontally-extended area of clouds known as the “cirrus canopy.” This region of cold cirrus is formed as intense convection lofts condensate into the upper troposphere and lower stratosphere, where it affects its immediate environment through latent heating and interaction with radiation. An increasingly large body of work shows that physical processes within the cirrus canopy can feed back onto the storm circulation and affect its track, size, and intensity. Until recently, however, the structure of the TC cirrus canopy has not been well-documented in observations. This paper presents aircraft reconnaissance observations of the TC cirrus canopy from the NASA Hurricane and Severe Storm Sentinel (HS3) and Office of Naval Research Tropical Cyclone Intensity Experiment (TCI) field campaigns. Strong stable layers are observed in the upper troposphere of TCs, particularly in regions of very cold cirrus. Possible causes of these stability maxima are presented, along with their potential implications for TC structure and evolution. Vertical cross-sections are constructed along flight legs conducted through Hurricane Patricia (2015) during TCI. Dropsondes were deployed once every minute across the cirrus canopy, constituting an unprecedented spatial resolution for dropsondes deployed in a hurricane. Using these cross-sections, the fine-scale variability in the upper troposphere – including the tropopause height and cold point temperature – will be analyzed.