Advances in global wave modelling

At MetOcean Solutions, we continuously improve our models to ensure the highest possible performance.

Our science team has recently made great improvements in global wave hindcasting thanks to using more accurate historical winds and studying the effect of icebergs and ocean currents in ocean waves.

MetOcean’s Southern Ocean Programme in partnership with Defence Technology Agency has been collecting wave data in the Southern Ocean over the last 2 years (find out more at www.metocean.co.nz/southern-ocean). The area presents the highest modelling errors, and the data gathered is helping to reduce that. This is a crucial achievement due to the energetic swells constantly generated in this part of the ocean that have far reaching effects. Consequently, it will result in better wave prediction over coastal areas.

MetOcean Solutions’ physical oceanographer Dr Jorge Perez, responsible for improving wave hindcasting and forecasting capabilities, says the analysis undertaken and the historical reconstruction has made it possible to minimize errors in wave data from deep waters, allowing better boundary conditions for high-resolution grids in coastal regions.

“Lessons learned such as the importance of currents and icebergs will result in advancements to our wave forecasting operational systems and therefore, historical data and wave predictions of the highest quality to end users.”

Clear gains are apparent, with an approximate 30% improvement in model skill demonstrated overall. The resulting improvements for the year of 2015 are shown as an example in the figure below.

 
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Example of bias comparison with model improvements (top) and reference simulation (bottom) for the year 2015.

Example of bias comparison with model improvements (top) and reference simulation (bottom) for the year 2015.

 

MetOcean’s advancements in global wave modelling were presented by Dr Perez at Spanish Conference on Coastal and Port Engineering, XV Jornadas Españolas de Ingeniería de Costas y Puertos, held last week in Málaga, Spain.

The conference is a biennial scientific-technical event, gathering experts and decision makers to facilitate knowledge exchange between all sectors engaged in coastal and port activities. For more information, visit www.costasypuertos2019.com

MetOcean Solutions is a division of New Zealand’s National Meteorological Service.

The full abstract is provided below.


Avances en modelado de oleaje global

Pérez, Jorge* Rapizo, Henrique* Guedes, Rafael* y Durrant, Tom*

*Metocean Solutions, New Zealand Meteorological Service.

1.       Introducción

El modelado de oleaje a escala global ha experimentado un rápido desarrollo en los últimos años dando lugar a reconstrucciones históricas cada vez más precisas (e.g., Durrant et al., 2014; Pérez et al., 2017). No obstante, incluso las bases de datos más recientes presentan errores significativos en ciertas regiones. Esto plantea una doble problemática. Por un lado, la creciente internacionalización de los intereses de empresas e instituciones hace evidente la necesidad de contar con datos de calidad en todo el mundo. Por otro lado, los errores en una ubicación específica a menudo son consecuencia de errores a miles de kilómetros de distancia, en la zona de generación o propagación. Por ejemplo, el Océano Antártico es la región que actualmente presenta mayores errores; en parte porque es un área muy compleja desde el punto de vista del modelado y en parte por la tradicional escasez de medidas instrumentales en el hemisferio sur. No obstante, es crucial reducir dichos errores, ya que constituye la zona de generación de swells muy energéticos que alcanzan las costas de regiones mucho más pobladas.

La forma de más obvia de reducir errores es utilizar forzamientos (i.e., viento, hielo y corrientes) de mayor calidad. En este análisis se han utilizado y comparado las bases de datos más recientes para obtener la combinación de forzamientos que resulta en menores errores en el modelado de oleaje a escala global. Como es habitual en han analizado vientos y cobertura de hielo, en este caso del reanálisis CFSR generado por NCEP-NCAR y del reanálisis ERA5 generado recientemente por el centro europeo para predicciones de medio plazo (ECMWF). Adicionalmente, se han analizado el efecto de la probabilidad de icebergs derivada de imágenes de satélite y de las corrientes oceánicas de tres bases de datos: CFSR, HYCOM y GLORYS. La evaluación de los resultados se ha basado principalmente en mediciones de satélite, pero se ha complementado con boyas y drifters recientemente desplegados en Australia y Nueva Zelanda.

2.       Resultados y conclusiones

Fig. 1. Sesgo respecto a datos de satélite de la simulación global forzada con vientos de ERA5, icebergs, y corrientes GLORYS (panel superior) y la simulación de referencia, forzada con vientos de CFSR y sin icebergs ni corrientes (panel inferior) para el año 2015.

Fig. 1. Sesgo respecto a datos de satélite de la simulación global forzada con vientos de ERA5, icebergs, y corrientes GLORYS (panel superior) y la simulación de referencia, forzada con vientos de CFSR y sin icebergs ni corrientes (panel inferior) para el año 2015.

La comparación entre experimentos con distintos forzamientos se ha basado en el modelo numérico WaveWatch III en su versión 5.16 utilizando los términos fuente ST4. La configuración de referencia es una malla global de 0.5 grados por 0.5 grados, forzada con vientos y cobertura de hielo de CFSR, sin icebergs ni corrientes. La mejora de mayor magnitud respecto a esta configuración se obtiene al sustituir CFSR por ERA5, lo que reduce notablemente el sesgo y el error cuadrático en la mayor parte del mundo. Estos resultados indican que las mejoras en resolución, asimilación de datos, o modelado de ciclones tropicales respecto al anterior reanálisis del ECMWF han conseguido que actualmente ERA5 sea la opción más adecuada para forzar modelos globales de oleaje. La inclusión de corrientes también produce mejoras a nivel global pero de una magnitud menor. En concreto las tres bases de datos de corrientes ayudan a reducir los sesgos, siendo GLORYS la que produce mejores resultados a pesar de tener menor resolución espacial que HYCOM y menor resolución temporal que CFSR. Es especialmente notable la reducción del sesgo positivo en el Océano Antártico, principalmente por el efecto de la corriente circumpolar antártica, que reduce la transferencia de energía del viento al oleaje. No obstante, incluso con la introducción de corrientes sigue existiendo un sesgo positivo. Este sesgo se reduce aún más con la inclusión de icebergs, que aumentan el bloqueo de energía, pero no llega a desaparecer por completo. La comparación entre el sesgo de la configuración de referencia y el de la configuración óptima para el año 2015 se muestra en la figura 1. La comparación de errores cuadráticos (no mostrado) indica mejoras globales en torno al 30%.

Este análisis a escala global y la reconstrucción histórica resultante ha permitido minimizar los errores en los datos de oleaje en aguas profundas y disponer de mejores condiciones de contorno para las mallas de detalle en zonas costeras. Adicionalmente, lecciones aprendidas de este análisis, como la importancia de corrientes y icebergs, van a resultar en mejoras en los sistemas operacionales de predicción de oleaje de Metservice. Esto permite proporcionar a los usuarios datos históricos y predicciones de oleaje de la mayor calidad posible.

Agradecimientos

Se agradece el apoyo a este estudio tanto de la armada de Nueva Zelanda (NZ Navy) como de la oficina de investigación naval (Office of Naval Research, ONR) por medio de la subvención NOOO14-17-S-B001.

Referencias

DURRANT, T., GREENSLADE, D., HEMER, M. y TRENHAM, C. (2014). “A Global Hindcast focussed on the Central and South Pacific”. CAWCR Technical Report , 46.

PEREZ, J., MENENDEZ, M. y LOSADA, I. J. (2017). “GOW2: A global wave hindcast for coastal applications”. Coastal Engineering, 124 , 1-11 .

Meet us at SIOP 2018 in Chile

Next week, Dr Aitana Forcén-Vázquez, MetOcean Solutions’ Technical Support Liaison, will be at the International Seminar of Engineering and Port Operations - SIOP 2018 in Chile.

“We are delighted to come for the second time to the International Seminar of Engineering and Port Operation, in its eighth edition, organised by ‘Empresa Portuaria Talcahuano San Vicente’,” says Aitana. “In this occasion, we will discuss about long waves and how its forecast helps port operations.

“We will discuss the challenges behind an accurate forecast and solutions we have been implementing on this side of the Pacific for the last 10 years.”

MetOcean Solutions, BENTOS and OMC International at the AAPA Convention 2018 in Valparaiso, Chile.

At the 107th American Association of Port Authorities Annual Convention next week, MetOcean Solutions together with recognised world-leader in real time under keel clearance management technology, OMC International, and local partner BENTOS will be presenting tailored solutions designed to increase safety and efficiency of marine operations.

“Together we have a skill set that allows us to provide comprehensive services, maximising the benefits to ports and harbours,” says Sébastien Boulay, MetOcean Solutions’ Business Development Scientist.

“The environmental conditions met by the ports along the Chilean coast are very similar to those in New Zealand. Our expertise of the oceanic conditions and their operational impact in the Southern Pacific, brought by decades of studying the New Zealand and Australia wave climates, is now available to the maritime industry in Chile for those willing to improve their operational safety and efficiency.”

The APPA Annual Convention is the largest port event in the Americas and this year is hosted by Port of Valparaíso and American Association of Ports Authorities, an alliance of ports from Canada, the Caribbean, Latin America and the United States. After several editions, the event returns to Latin America and for the first time it is held in South America on 7-10 October in Valparaíso, Chile, gathering key worldwide industry leaders to discuss the main port projects.

Click here for more information on the convention.

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Peter McComb in Southern Ocean seminar at Valparaiso University, Chile

MetOcean Solutions is visiting Chile this week.

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As part of the visit, Managing Director Dr Peter McComb will give a seminar on Friday 5 May at Valparaiso University. The seminar will detail the Southern Ocean wave project, a collaboration between the New Zealand Defence Technology Agency and MetOcean Solutions. As part of the project, MetOcean Solutions helped deploy the world's southernmost moored wave buoy in February 2017.

Dr McComb is excited to share the Southern Ocean project with colleagues in Chile. 

"Southern Ocean waves are famously enormous. Created by persistent westerly winds and a large fetch of uninterrupted ocean, these waves present serious obstacles for any vessels operating in the area. Understanding the dynamics of the Southern Ocean can help us forecast wave conditions, which is important for any nation located close to the Antarctic. 

"As a world first, New Zealand has installed an open ocean wave buoy in the Southern Ocean which can measure the huge waves and provide essential data to help us understand the area. Data collected will be used to improve our models, enabling us create more reliable wave forecasts for the region. We are keen to share data with our Chilean colleagues to ensure that the world science community benefits as much as possible from the project."

The full abstract of the talk is provided below.

An improved wave spectral characterisation of the Southern Ocean
Tom Durrant*, Peter McComb* and Sally Garrett^

The Southern Ocean is the southernmost part of the global ocean and represents around 22% of the world's sea surface area. The combination of persistent westerly winds and the largely unbroken expanse of sea produces potentially enormous fetches, resulting in the Southern Ocean experiencing higher wave heights for longer periods than any other body of water. Due to the harsh ocean environment and remote location, it is also the least observed of any ocean body. While satellite altimeter data can be used to estimate the surface variance, the wave spectral characteristics cannot be measured remotely, and consequently the directional wave spectra Southern Ocean are poorly sampled and not well understood. Here, we present a project that aims to provide a quantitative assessment of the performance of recently implemented improvements of source term physics in WAVEWATCH III in the Southern Ocean, including an analysis of the relative importance of large scale ocean currents. A moored wave buoy at 53 degrees South is an important part of the project scope, and the deployment of this equipment and the data obtained since February 2017 will be presented and discussed.

*MetOcean Solutions. ^ New Zealand Defence Technology Agency

Check out the Southern Ocean wave buoy direct data feed.

Read the New Zealand Herald news article on the project.

Click here for further information about the buoy.  

High resolution wave forecasts for Chile now available

GOOD FORECASTS IMPROVE PORT SAFETY AND EFFICIENCY.

GOOD FORECASTS IMPROVE PORT SAFETY AND EFFICIENCY.

MetOcean Solutions have set up a high resolution wave forecast model for the coastline of Chile in South America. 
 
"We are delighted to now provide a high quality wave model for Chile," says Senior Oceanographer Dr Rafael Guedes. "We've set up a regional domain covering the central and northern Chilean coast and can now provide nearshore wave forecasts for the area north of 41°S. Accurate wave forecasting is important for ports located along this dynamic, exposed coastline."

THE CHILE MODEL DOMAIN, SHOWING DEPTH (LEFT) AND SAMPLE WAVE HEIGHT (RIGHT).

THE CHILE MODEL DOMAIN, SHOWING DEPTH (LEFT) AND SAMPLE WAVE HEIGHT (RIGHT).

The work was initiated following a visit by MetOcean Solutions to Chile in October, where the need for high resolution port scale wave forecasts was made apparent.  
 
"We've used the state-of-the-art SWAN (Simulating WAves Nearshore) model," continues Dr Guedes. "Like many New Zealand ports, Chilean ports suffer from wave exposure. Accurate modelling can help ports save money and time, and increase safety. MetOcean Solutions specialise in forecasting wave conditions for weather-exposed ports, and we provide expert forecasts for a number of ports internationally already. We are very happy to potentially extend the service to Chile. Of course, very high accuracy forecasts require accurate bathymetry." 
 
The model domain was set up to cover the coast between 41°S and 17°S at 5 km resolution and was set up using full spectral boundaries from MetOcean Solutions' new, upgraded global WAVEWATCH III wave model. The new model can be accessed via the MetOceanView platform.

MetOcean at SIOP 2016 in Chile

Operational Oceanography applied to ports

Operational Oceanography applied to ports

Dr Peter McComb, que vino a San Antonio (Chile) como motivo del Seminario Internacional de Ingeniera y Operación Portuaria (SIOP 2016), fue invitado a dar una ponencia sobre el tema de la Oceanografía Operacional y las soluciones existentes para puertos.

"Fue un honor participar en un evento de tal importancia", comentó Peter. "Es siempre muy interesante tener conocimiento de las iniciativas científicas y compartir lo que hacemos",  añadió.

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Dr Peter McComb recently attended the International Seminar of Engineering and Port Operations (SIOP 2016) conference held in San Antonio, Chile. Peter was invited to talk about Operational Oceanography and solutions for ports. 

"It was an honour to be invited to present at the SIOP 2016 conference," states Peter. "It was great to hear about all the science initiatives in that part of the world, and to share what we do."

For the full video of conference talks, see the  Puerto San Antonio Facebook link.