Wave Measurements From Radar Tide Gauges

Laura A Fiorentino,Robert Heitsenrether,Warren Krug

doi:10.3389/fmars.2019.00586

Laura A Fiorentino, Robert Heitsenrether + Show 1 more

Open Access

https://doi.org/10.3389/fmars.2019.00586

Copy DOI

Abstract

Currently the NOAA Center for Operational Oceanographic Products and Services (CO-OPS) is transitioning the primary water level sensor at most NWLON stations from an acoustic ranging system to microwave radars. With no stilling well and higher resolution of the open sea surface, microwave radars have the potential to provide real-time wave measurements at NWLON sites. Radar sensors at tide stations may offer a low cost, convenient way to increase nearshore wave observational coverage throughout the U.S. to support navigational safety and ocean research applications. Here we present the results of a field study comparing wave height measurements from four radar water level sensors with two different signal types (pulse and continuous wave swept frequency modulation-CWFM). A nearby bottom acoustic wave and current sensor is used as a reference. An overview of field setup and sensors will be presented, along with an analysis of performance capabilities of each radar sensor. The study includes results from two successive field tests. In the first, we examine the performance from a pulse microwave radar (WaterLOG H-3611) and two CWFM (Miros SM-94 and Miros SM-140). While both types of radars tracked significant wave height well over the test period, the pulse radar had less success resolving high frequency wind wave energy and showed a high level of noise towards the low frequency end of the spectrum. The pulse WaterLOG radar limitations were most apparent during times of high winds and locally developing seas. The CWFM radars demonstrated greater capability to resolve those higher frequency energies while avoiding low frequency noise. The initial field test results motivated a second field test, focused on the comparison of wave height measurements from two pulse radar water level sensors, the WaterLOG H3611 and the Endress and Hauser Micropilot FMR240. Significant wave height measurements from both radar water level sensors compared well to reference AWAC measurements over the test period, but once again the WaterLOG radar did not adequately resolve wind wave energy in high frequency bands and showed noise towards the low frequency end of the spectrum. The E+H radar demonstrated greater capability to measure waves.

Highlights

The National Oceanic and Atmospheric Administration (NOAA) National Ocean Service (NOS) Center for Operational Oceanographic Products and Services (CO-OPS) maintains and develops the National Water Level Observation Network (NWLON), which consists of over 200 long-term stations that provide real-time water level observations across coasts in the U.S
We present the results of our second ongoing study on the use of microwave radar water level sensors for wave measurements, with a focus on the comparison of wave height measurements from two pulse radar water level sensors, the WaterLOG H3611 and the Endress+Hauser Micropilot M FMR240
The first of two field tests conducted by CO-OPS at the Duck, NC NWLON station indicate that the higher cost, higher power Miros SM-140 continuous wave frequency modulated (CWFM) radar sensor outperformed the pulse type radar water level sensor that is currently being transitioned across NWLON, the WaterLOG H3611

Summary

Introduction

The National Oceanic and Atmospheric Administration (NOAA) National Ocean Service (NOS) Center for Operational Oceanographic Products and Services (CO-OPS) maintains and develops the National Water Level Observation Network (NWLON), which consists of over 200 long-term stations that provide real-time water level observations across coasts in the U.S. The primary water level measurement system at most stations is an acoustic ranging water level sensor. In 2012 COOPS began to transition NWLON station sensors from acoustic to microwave radar water level sensors, which provide many benefits, including lower costs, less maintenance and support, and improved measurements (Park et al, 2014). Employing the same single sensor to simultaneously measure both surface gravity waves and longer average water levels, offers an efficient system design and significant savings in costs

Methods

Results

Conclusion