The objective of this research is to develop an improved understanding of the convective response of a tropical cyclone's core to external forcing and internal dynamics. The impact of this convective response upon the ensuing evolution of an externally forced tropical cyclone will also be examined. In the particular case of a vertically sheared tropical cyclone, convection has been argued to have both positive and negative influences on vortex structure and intensity. This study will attempt to define the role of convection by examining the impact of vertical shear on a moist-convective vortex within a simplified wave-mean dynamical framework.
The research employs a combined observational and numerical modeling approach. The observations include airborne dual-Doppler radar measurements within a rapidly intensifying, yet vertically-sheared, hurricane. A unique three-dimensional documentation of the hurricane structure and evolution, including the eyewall interface and upper-tropospheric vortex circulation, will be used to examine the nature, timing, and location of convection within the vortex core. These observations will be used to represent convection in a series of idealized numerical simulations. The idealized simulations are designed to elucidate the role of convection in tropical cyclone resiliency and to determine how and when convection begins to impact the tropical cyclone negatively.
Intellectual Merit: The research will provide new insights into i) the observed three-dimensional mixing between eye and eyewall within a rapidly intensifying hurricane, ii) the observed convective asymmetry within a vertically-sheared hurricane, iii) the role of convection in vertically-sheared hurricane resiliency, and iv) the role of deep cumulus convection in the weakening of a vertically-sheared hurricane.
Broader Impacts: The research activities will have several broader impacts. Regarding hurricanes: Presently, there exists a single observational study of the three-dimensional hurricane vorticity dynamics. The case study to be undertaken will be an important step towards increasing the statistical database of three-dimensional observations, which is crucial if such data are to be meaningfully assimilated into mesoscale numerical forecast models. Additionally, the mapping of effective stratification based on observed data within the hurricane core may be used by future investigators for idealized numerical modeling. More generally: The convection-vortex interaction is a general atmospheric problem (e.g., mid-latitude MCVs) and has parallels with the convectively-coupled equatorial wave problem. This study will draw upon this broader knowledge base, and in return will contribute beyond the scope of hurricanes. Two graduate students and an undergraduate will be trained in the techniques of radar data editing and analysis, atmospheric dynamics, and numerical modeling. These students will also be encouraged to interact with scientists at NOAA's Hurricane Research Division through their ongoing cooperation with the universities.
