PAOC Colloquium: Kristen Corbosiero (U Albany)
Diagnosis of Secondary Eyewall Formation Mechanisms in Hurricane Igor (2010)
Despite being a common feature of major hurricanes and exhibiting a strong relationship with storm intensity change, there exists no unified theory explaining secondary eyewall formation (SEF) in tropical cyclones. In recent years, a number of hypotheses have been proposed for SEF with the most substantive difference among them being the relative roles of internal dynamics and external, environmental forcing. Examples of the former involve vortex Rossby wave-mean flow interaction, anisotropic upscale energy cascade, and unbalanced boundary layer spinup, while examples of the later include wind-induced surface heat exchange being triggered by external forcing and environmental humidity controlling storm size and rainband structure. This last factor, the moisture distribution and rainband activity outside the tropical cyclone core, appeared to be important in our previous research examining ensemble forecasts of Hurricane Igor (2010): ensemble members that undergo SEF exhibit a more uniform moisture distribution relative to the members that do not, with the moisture originating in active outer rainband convection upshear of the center. The rainbands flood the boundary layer with low moist static energy air, which propagates cyclonically around the center as a cold pool. We hypothesized that enhanced convergence between the cold pool and low-level inflow reinvigorated the rainband convection that became the secondary eyewall.
To test our rainband reinvigoration hypothesis, as well as the other SEF hypotheses noted above, we will analyze the 16 (out of 96) ensemble members of the NCAR Advanced Hurricane Weather Research and Forecasting model that exhibited SEF in Hurricane Igor (2010) at high spatial (1.33 km) and temporal (10 min) resolution. Specifically, we will: 1) diagnose the role of vertical wind shear in determining the distribution and evolution of moisture and outer rainbands, 2) calculate moist static energy and angular momentum budgets, 3) investigate the existence of vortex Rossby waves and whether they interact with the mean vortex at their stagnation radius, and 4) look for the hallmarks of the unbalanced spinup paradigm, e.g., the generation of supergradient winds in the boundary layer, strengthening of the low-level inflow, and an eruption of air from the boundary layer to support convection.
About the Speaker
My research focuses on the interaction between tropical cyclones and the environments in which they are embedded, with an emphasis on storm structure, the intensity and duration of convection, and the properties of clouds that comprise the storm.
I have tackled these problems using both observational data and numerical modeling, and my work has documented the critical role of storm asymmetries on both intensity and track.
About this Series
The PAOC Colloquium is a weekly interdisciplinary seminar series that brings together the whole PAOC community. Seminar topics include all research concerning the physics, chemistry, and biology of the atmospheres, oceans and climate, but also talks about e.g. societal impacts of climatic processes. The seminars generally take place on Monday from 12-1pm. Lunch is provided to encourage students and post-docs to meet with the speaker. Besides the seminar and lunch, individual meetings with professors, post-docs, and students are arranged.