Abstract
This study analyses Global Positioning System dropsondes to document the axisymmetric tropical cyclone (TC) boundary-layer structure, based on storm intensity. A total of 2608 dropsondes from 42 named TCs in the Atlantic basin from 1998 to 2017 are used in the composite analyses. The results show that the axisymmetric inflow layer depth, the height of maximum tangential wind speed, and the thermodynamic mixed layer depth are all shallower in more intense TCs. The results also show that more intense TCs tend to have a deep layer of the near-saturated air inside the radius of maximum wind speed (RMW). The magnitude of the radial gradient of equivalent potential temperature (θe) near the RMW correlates positively with storm intensity. Above the inflow layer, composite structures of TCs with different intensities all possess a ring of anomalously cool temperatures surrounding the warm-core, with the magnitude of the warm-core anomaly proportional to TC intensity. The boundary layer composites presented here provide a climatology of how axisymmetric TC boundary layer structure changes with intensity.
Highlights
Tropical cyclones (TCs) typically form over warm ocean regions and may strengthen when the environmental factors are favorable
(2010, [19,20]), as well as in studies using a composite approach [21,22]. This present study aims to investigate the relationship of the axisymmetric TC boundary-layer structure and storm intensity by compositing dropsonde data from multiple TCs
This study constructed composites of dropsonde data to study the low-level structure of TCs of
Summary
Tropical cyclones (TCs) typically form over warm ocean regions and may strengthen when the environmental factors are favorable. Accurate forecasts of TC track and intensity in numerical weather prediction models depend on multiple factors, but one important requirement is that the TC structure should be accurately represented. Other aspects of the low-level TC structure have been investigated in several case studies, such as in Hurricanes Bonnie (1998, [15]), Edouard (2014, [16,17,18]), and Earl (2010, [19,20]), as well as in studies using a composite approach [21,22] This present study aims to investigate the relationship of the axisymmetric TC boundary-layer structure and storm intensity by compositing dropsonde data from multiple TCs. The objective is to create an observations-based climatology of the symmetric low-level (i.e., boundary layer) structure of a TC. Improved understanding of TC structural variation in response to storm intensity will provide useful information for forecasters to narrow the range of uncertainty in the intensity forecast, especially before TC landfalls
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