Intercomparison of Wave Observations within Tropical Cyclones

Ocean waves in tropical cyclones present significant spatial variations and rapid growth, in response to storm intensity, size, and speed. Modeling and forecasting hurricane-generated waves is challenging, requiring high-quality and dense sets of observations (preferably in the 2D full spectrum) which are employed for data assimilation and physics optimization. The high wind-generated wave processes in scales from centimeter to kilometer, along with the wave-wave interactions and the presence of large and steep waves, make traditional moored buoy systems insufficient - demanding additional observations, such as drifting buoys and airborne radar altimetry. In this study, we analyze and compare several different wave observations collected within tropical cyclones. Our focus is on the Atlantic Ocean, in deep water areas, covering three years, from 2022 to 2024.

The wave observations selected include:

- Two sources of accelerometer buoys (moored): the National Data Buoy Center (NDBC) and the Coastal Data Information Program (CDIP);

- Three types of GPS drifting buoys: microSWIFT (Applied Physics Laboratory, University of Washington), spotter (Sofar Ocean), and Directional Wave Spectra Drifter (DWSD, Lagrangian Drifter Laboratory, Scripps Institution of Oceanography);

- Two types of radar aboard the NOAA Hurricane Hunter P-3 aircrafts: the Wide Swath Radar Altimeter (WSRA) and the Ka/Ku-band Interferometric Altimeter (KaIA);

- Eight satellite altimeter missions, quality controlled and calibrated by the Australian Ocean Data Network (AODN): CFOSAT, SARAL, CRYOSAT2, HY2B, JASON3, SENTINEL3A, SENTINEL3B, and SENTINEL6A.

First, the buoys (moored and drifting) and altimeter radars (from the P-3 aircraft and satellite) are collocated using spatio-temporal criteria, providing a broad multiscale view of hurricane-generated waves. Then, a multiple collocation statistical analysis is applied, where systematic and scatter differences, as well as correlations, are examined. Special extreme events, such as Hurricanes Fiona (2022), Ian (2022), Idalia (2023), Franklin (2023), and Lee (2023), are used to illustrate the intercomparisons. The combination of fixed-position buoys, targeted deployments of drifting buoys, airborne radars, and satellite altimetry provides a highly dense set of observations capable of accurately representing the cyclones while allowing a thorough evaluation of the uncertainties.