Small-Scale Features Observed in the Boundary Layer of Hurricanes Isabel (2003) and Frances (2004)

The hurricane boundary layer (HBL) has been intensively studied in the tropical meteorology community as it is the region of the hurricane that affects society. Recent observational studies as well as modelling studies suggest that HBLs are prone to containing small-scale features that can be a significant factor in the vertical transfer of momentum, heat and moisture. However, little is known about the specific characteristics of these small-scale features. Recently, analyses have been conducted using WSR-88D radar data, which led to a better representation of some of these features. Unfortunately, the coarse spatial and temporal resolution of operational radars has been a limiting factor in enabling a more precise description of the BL small-scale features.

In an attempt to answer interrogations about the physical characteristics of these small-scale features, their motion and their circulation, the Texas Tech University Hurricane Intercept Team collected data during the landfall of Hurricanes Isabel (2003) and Frances (2004) using the SMART-Radars. The primary goal of the experiments was to acquire high spatial and temporal resolution data of the HBL in order to identify and document these features in a more precise manner. Various scanning strategies, including RHIs and fast PPIs were specifically designed to document the HBLs. These strategies, along with a rather small gate spacing (66.5 m) and intensive data processing involving a VAD technique, FFT analysis and image processing allowed for the identification of detailed structures in both hurricanes. Characteristics of these features have been successfully retrieved and documented. These results could, in the near future, lead to a more comprehensive three-dimensional representation of these small-scale features and help provide a better understanding of the overall HBL structure.