A relocatable ocean modelling platform for downscaling to shelf-coastal areas to support disaster risk reduction

High-impact ocean weather events and climate extremes can have devastating effects on coastal zones and small islands. Marine Disaster Risk Reduction (DRR) is a systematic approach to such events, through which the risk of disaster can be identified, assessed and reduced via direct observations, thus improving ocean and atmosphere prediction models and the development of efficient early warnings systems. A common user request during disaster remediation actions is for high-resolution information, which can be derived from easily deployable numerical models nested into operational larger-scale ocean models.

The Structured and Unstructured Relocatable Ocean Model for Forecasting (SURF) has been designed to provide operational ocean forecasting communities with the means to rapidly deploy a nested high-resolution numerical model into larger-scale ocean forecasts. Rapidly downscaling the current, sea level and temperature, and salinity fields is critical in supporting emergency response and DRR planning, which are typically related to very localized areas in the world’s oceans. The first and most important requirement in a relocatable modelling capability is to ensure all of the interfaces have been tested through low-resolution operational ocean analyses, forecasts and atmospheric forcing. The provision of continuous ocean circulation forecasts through the Copernicus Marine Environment Monitoring Service (CMEMS) enables this testing. High-resolution SURF ocean circulation forecasts can then be accessed through specific numerical application model interfaces that require the knowledge of meteo-oceanographic conditions, such as oil spill forecasting, search and rescue modelling, and ship routing modelling for safe navigation.

SURF was used to downscale CMEMS circulation analyses in four world ocean regions, and the high-resolution currents it can simulate for specific applications are examined. The SURF downscaled circulation fields show that the marine current resolutions affect the quality of the application models to be used for assessing disaster risks, particularly near coastal areas where the coastline geometry must be resolved through a numerical grid, and high-frequency coastal currents must be accurately simulated.