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Jacob Davis

Research Assistant

Email

jdavis@apl.washington.edu

Publications

2000-present and while at APL-UW

Ocean surface wave slopes and wind-wave alignment observed in Hurricane Idalia

Davis, J.R., J. Thomson, I.A. Houghton, C.W. Fairall, B.J. Butterworth, E.J. Thompson, G. de Boer, J.D. Doyle, and J.R. Moskaitis, "Ocean surface wave slopes and wind-wave alignment observed in Hurricane Idalia," J. Geophys. Res., 130, doi:10.1029/2024JC021814, 2025.

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1 Feb 2025

Drifting buoy observations in Hurricane Idalia (2023) are used to investigate the dependence of ocean surface wave mean square slope on wind, wave, and storm characteristics. Mean square slope has a primary dependence on wind speed that is linear at low-to-moderate wind speeds and approaches saturation at high wind speeds (>20 m s-1 ). Inside Hurricane Idalia, buoy-measured mean square slopes have a secondary dependence on wind-wave alignment: at a given wind speed, slopes are higher where wind and waves are aligned compared to where wind and waves are crossing. At moderate wind speeds, differences in mean square slope between aligned and crossing conditions can vary 15–20% relative to their mean. These changes in wave slopes may be related to the reported dependence of air-sea drag coefficients on wind-wave alignment.

Multiscale measurements of hurricane waves using buoys and airborne radar

Davis, J.R., J. Thomson, B.J. Butterworth, I.A. Houghton, C. Fairall, E.J. Thompson, and G. de Boer, "Multiscale measurements of hurricane waves using buoys and airborne radar," In Proc., IEEE/OES 13th Current, Waves and Turbulence Measurement (CWTM), 18-20 March 2024, Wanchese, NC, doi:10.1109/CWTM61020.2024.10526332 (IEEE, 2024).

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15 May 2024

The processes important to hurricane wave generation cover scales from kilometers to centimeters. Within a storm, waves have complex spatial variations that are sensitive to hurricane size, strength and speed. This makes it challenging to measure the spatial variability of hurricane waves with any single instrument. To obtain both broad spatial coverage and resolve the full range of wave scales, we combine arrays of drifting wave buoys with airborne radar altimetry. The microSWIFT (UW-APL) and Spotter (Sofar) buoys are air-deployed along a given storm track. These buoys resolve the scalar wave frequency spectrum from 0.05 Hz to 0.5 Hz, which is approximately 600 m to 6 m wavelength (in deep water). The Wide Swath Radar Altimeter (WSRA) flies into hurricanes aboard the NOAA Hurricane Hunter P-3 aircraft. The radar altimetry data is processed to produce a 2D directional spectrum from 2.5 km to 80 m wavelength, and the radar backscatter provides an estimate of the mean square slope down to centimeter wavelengths. We introduce a method to use colocated mean square slope observations from each instrument to infer the shape of the spectral tail from 0.5 Hz to almost 3 Hz. The method is able to recover the frequency f–5 tail characteristic of the saturation range expected at these frequencies (based on theory and measurements in lower wind speeds). We also explore the differences between WSRA and buoy mean square slopes, which represent the mean square slope of the intermediate wavelength waves (6 m down to 20 cm). Together, the fusion of these wave measurements provides a multiscale view of the hurricane-generated waves. These ocean surface waves are critical as drivers of the air-sea coupling that controls storm evolution and as drivers of coastal impacts by hurricanes.

Development and testing of microSWIFT expendable wave buoys

Thomson, J., P. Bush, V.C. Contreras, N. Clemett, J. Davis, A. de Klerk, E. Iseley, E.J. Rainville, B. Salmi, and J. Talbert, "Development and testing of microSWIFT expendable wave buoys," Coastal Eng. J., EOR, doi:10.1080/21664250.2023.2283325, 2023.

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22 Nov 2023

Expendable microSWIFT buoys have been developed and tested for measuring ocean surface waves. Wave spectra are calculated via onboard processing of GPS velocities sampled at 5 Hz, and wave spectra are delivered to a shore-side server via Iridium modem once per hour. The microSWIFTs support additional sensor payloads, in particular seawater conductivity and temperature. The buoys have a non-traditional, cylindrical shape that is required for deployment via the dropsonde tube of research aircraft. Multiple versions have been developed and tested, with design considerations that include: buoy hydrodynamics, sensor noise, algorithm tuning, processor power, and ease of deployment. Field testing in a range of conditions, including near sea ice and in a hurricane, has validated the design.

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Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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