Ventilation Processes and Effects on Tropical Cyclones

Suny At Albany, Albany NY

Investigators

Abstract

Tropical cyclone development is significantly affected by the presence of dry air and wind shear. Wind shear can interact with the tropical cyclone vortex through a process called ventilation to inject cool, dry environmental air into the tropical system. While it is well known that these processes exist, there is significant uncertainty as to how ventilation occurs and how it modulates tropical cyclone development. This project will shed light on these issues by conducting a series of high-resolution numerical modeling simulations. The main societal impact of the project will be improved knowledge of the factors that affect hurricane intensity, which is especially important for forecasts of hurricanes near populated and vulnerable areas. The researchers also plan outreach events for students and the general public to enhance scientific literacy. Two early career researchers will also be educated and trained under this project, ensuring the development of a highly capable workforce. The research team plans an idealized modeling study to increase understanding of how dry air and vertical wind shear work synergistically through the process of ventilation to modulate tropical cyclone development. The CM1 model will be used with different combinations of vertical wind shear and relative humidity, starting from tropical cyclones states with different initial intensities. The simulations will be analyzed to test the following hypotheses: 1) low- and mid-level ventilation both increase as the relative humidity decreases and the vertical wind shear increases, but the ventilation pathway depends on the intensity of the TC, 2) mid-level ventilation is accomplished by vortex Rossby waves in the inner core and descending radial inflow in the stratiform region of TC rainbands, 3) ventilation increases lateral entrainment of low-moist static energy air into convection and convective/turbulent mixing of low-moist static energy air into the boundary layer, thereby weakening TC convection and the secondary circulation. 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.