Weather Sentinels Hit the Beach
University of Florida researchers designing mobile weather stations tough enough for extreme coastal hazards
Published on June 2, 2023
(a) Field installation of the Sentinel Mark I prototype. (b) Mark I Sentinel design (Image: Brian Phillips)
Pedro Lomonaco, NHERI at OSU co-PI, and Ehsan Ahmadi Afzadi, UF PhD researcher (Image: Ehsan Ahmadi Afzadi)
For collecting data on extreme coastal storms and their effects, a research team led by the University of Florida is designing a fleet of large, robust, mobile weather stations. Called "Sentinels," these 10-meter-tall temporary structures can be installed directly on beaches in the littoral zone, secured by 6-meter-deep helical piles. Weather-hardened instrumentation will report on wind and wave loads, storm surge, coastal erosion and morphology changes, water quality, and other processes that occur during and after extreme coastal storms. The collocated and synchronized measurements are reported back to researchers in real-time over cellular networks.
A culminating effort. Natural-hazards watchers are familiar with the University of Florida's extreme wind research efforts. Since the late 90s, UF researchers led by Kurt Gurley and Forrest Masters have deployed mobile weather stations in landfalling hurricanes as part of the Florida Coastal Monitoring Program (FCMP). UF researchers erect the FCMP stations in strategic locations in the path of the hurricane to study surface-level wind fields.
The Sentinels are a natural progression of that work, filling in the observational gap in the near-shore region under combined hazards. Sentinels will support research in characterizing wind, storm surge, and wave impacts to civil and coastal infrastructure, predicting impacts to the nearshore water-land system, water quality monitoring during tropical cyclones and severe storms, and improving surface wind intensity estimates (e.g., numerical weather prediction and remote sensing). In 2021, Masters and his team successfully field-tested a prototype station, the Sentinel Mark I.
Based on early field tests of the Mark I Sentinel in 2022, a team led by UF researcher Brian Phillips landed an NSF Major Research Instrumentation (MRI) award to design a fleet of Mark II Sentinels as a shared-use resource. Design of these structures is underway.
Wave lab experiments. In 2023, for the MRI project design task, the team conducted experiments at OH Hinsdale Wave Lab at Oregon State University, a facility in the NSF-funded Natural Hazards Engineering Research Infrastructure. OSU's Directional Wave Basin is a reinforced-concrete reservoir about the size of an Olympic swimming pool. The DWB wavemaker can generate repeatable regular, irregular, tsunami and user-defined waves.
"Using the OSU facility, we can simulate dynamic breaking wave loads on the Sentinel," says project PI Phillips. "Experiments in the DWB are helping us better quantify breaking-wave forces and understand what can be done to reduce them on the station. We are exploring how changes in the Sentinel system's geometry and dynamics affect the wave loads."
One goal is to optimize the Mark II design for weight. "If we can reduce the wave impact forces, we can in turn reduce the Sentinel's structural weight — which will enable us to bring more Sentinels into the field on hurricane deployments. Additionally, installation will be quicker and require less equipment, allowing us to cover a greater swath of the coast prior to landfall," Phillips explains.
During two rounds of testing, the team installed a 1:10 prototype in the wave basin. First, working with OSU, they tuned the DWB wavemaker to achieve a variety of wave loading conditions on the scaled version of the Sentinel. In round two, the team explored how changes to the Sentinel design, both in geometry and dynamics, affected the breaking-wave loads.
Next phases. Phillips says the next step in the project is to work with the Mark I Sentinel during the 2023 hurricane season. The focus will be on installation, logistics, and instrumentation. Afterwards, the Mark II design will be finalized, bringing together the Mark I field studies, OSU experimental results, and engineering analysis and optimization. A prototype Mark II Sentinel will be deployed in the 2024 hurricane season followed by a full build for the following season.
Sentinel Mark II prototype subjected to rough waves.
One of the prototypes features a rotating mast.
Long view of the OSU wave maker and the Sentinel Mark II prototype in the Directional Wave Basin.
The scale model Sentinel Mark II in OSUs Directional Wave Basin. (Image: Ehsan Ahmadi Afzadi)
The 1:10 scale model Sentinel Mark II. (Image: Ehsan Ahmadi Afzadi)
Sentinel Mark II prototype, subjected to waves the OSU Directional Wave Basin (Image: Ehsan Ahmadi Afzadi)
Award Abstract #2215297
MRI: Development of a Shared-Use Experimental Platform to Study Wind, Hydrodynamic, and Biochemical Conditions in the Littoral Zone During Extreme Coastal Storms. Brian Phillips (PI); Forrest Masters (Co-PI); Elise Morrison (Co-PI) Maitane Olabarrieta Lizaso (Co-PI); Britt Raubenheimer (Co-PI)
Further reading:
An Experimental Platform to Study Wind, Hydrodynamic, and Biochemical Conditions in the Littoral Zone During Extreme Coastal Storms, Oceanography Magazine, Jan. 2023