Tropical Cyclones from 400 to 40 hPa

Tropical cyclones, also known as hurricanes and typhoons, are large and dangerous storms that cause significant damage and loss of life around the globe. The primary method of tracking and estimating the intensities of these storms is through viewing satellite images of the thick circular deck of high cirrus clouds that surround the center (or “eye”) of the storm, also known as the cirrus shield. This project will examine the sources and budgets of the moisture and condensate (ice and snow) in the cirrus shield and how this relates to the overall structure and intensity of the storm. It will also investigate to what extent the strongest thunderstorms in and around tropical cyclones are transporting ice to even higher altitudes, which may represent a source of water vapor molecules that play important roles in the chemistry of the stratosphere, with implications for the ozone layer and Earth’s climate. This project will investigate the dynamical processes and moist physics of the upper-level outflow that lies above all tropical cyclones (TCs). This outflow contains the central cirrus cloud shield seen by satellites that provide the vast majority of intensity estimates for all TCs around the globe. Occasional in-situ observations, airborne Doppler radar analyses, and increasingly realistic numerical simulations suggest that both the primary outflow, and also compensating inflow layers above and below, can have highly asymmetric structures, and are embedded with waves, dynamical instabilities, and overshooting cloud tops from strong updrafts. These overshooting updrafts may also be injecting moisture irreversibly into the stratosphere, possibly playing a non-trivial role in the water budget of the stratosphere. Airborne Doppler radar observations, dropsonde measurements, satellite images, and very high-resolution computer simulations will be used to better understand the three-dimensional structure of the outflow, including the adjacent inflow layers above and below the outflow. This project will focus on the structure, dynamics and moisture budgets of TCs across the lower and upper limits of these circulations, ranging from approximately 400 hPa (8 km) to 40 hPa (22 km) in altitude. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.