Tropical cyclones are responsible for extensive damage and loss of life in coastal and island communities around the globe. They have been studied for decades, but are not fully understood. Greater physical understanding of tropical cyclones will improve our ability to predict the behavior of individual storms and the effects of climate change on storm statistics. This project seeks further insight into the causes and consequences of tropical cyclone asymmetries, which are commonly associated with spiral rainbands, tilts and eyewall mesovortices. The following issues will be addressed: the extent to which environmental conditions control the dominant asymmetries, the mechanisms that create or suppress asymmetries, and the impact of asymmetries on vortex intensity.
This project will involve complimentary studies with reduced (3-layer) and cloud-system resolving (CSR) tropical cyclone models. The reduced model will facilitate an efficient computational survey of prevailing asymmetries under different environmental conditions. Moreover, it will be used to advance underdeveloped theories of core instabilities (which create asymmetries) and vortex resilience (resistance to tilt). The theoretical studies will focus on the roles of overturning circulation, boundary layer coupling, and diabatic forcing associated with moist convection. The effects of varying the surface-exchange coefficients, sea-surface temperature, mid-level relative humidity and cumulus parameterization scheme will be examined. Conclusions derived from the reduced model will be tested against CSR simulations, and any differences will be explained. The impact of transient and persistent asymmetries on vortex intensity will be assessed, partly by comparison of axisymmetric and 3D versions of the tropical cyclone models.
Funds for this project will be used in part for the advanced training and mentorship of a postdoctoral researcher. Project findings will be disseminated through university seminars, journal publications, conference presentations, and a research web page.
