A reassessment of the UK operational surge forecasting procedure

This report is a summary of the Met Office surge forecasting procedure for the UK, and some investigations into possible sources of error. The forecast is based on the "non-tidal residual", the difference of two model runs with and without weather effects, linearly added to the "astronomical prediction" from local tide gauge harmonics. This method is exposed to several errors. Here we do not attempt to quantify errors in the model or weather forcing, but we show how errors can arise in the harmonic analysis and due to the double counting of weather-related tides. The executive summary, validation guidelines and recommendations have been prepared jointly with the Met Office

Quantification of uncertainties in shoreline response to the representation of offshore wave conditions

This paper presents the results of a sensitivity study investigating beach/dune response to offshore wave boundary forcing. The modelling study was based on the convex-shape Sefton coast, UK which has a complex nearshore morphology with ridge-runnel patterns and foreshore frontal dunes. Simulations were performed using a cascade of nested grids to transform offshore waves up to a high resolution nearshore XBeach model of the Sefton coast in which the beach/dune response was modelled. Two storm events representing low and high severity were simulated using uniform and varying wave boundary conditions at the offshore model boundary for both cases. The uniform boundary always resulted in higher storm waves in the XBeach domain. There were differences along the coast based on the coastline orientation and the local morphology, indicating different localised sensitivities to the wave boundary type. Bed level change within the tidal regions (sub-, inter- and supra-tidal) indicated landward decrease of the wave boundary effect. Volume change within the sub-tidal area showed the highest sensitivity to the space varying wave boundary forcing. Applying a uniform wave boundary for the XBeach domain exacerbated the wave impacts in the model domain. Our study suggests that application of a spatially varying wave boundary condition for the XBeach domain was able to correctly capture sediment transport and hence the beach/dune response of Sefton coast

SEASTAR: a mission to study ocean submesoscale dynamics and small-scale atmosphere-ocean processes in coastal, shelf and polar seas

High-resolution satellite images of ocean color and sea surface temperature reveal an abundance of ocean fronts, vortices and filaments at scales below 10 km but measurements of ocean surface dynamics at these scales are rare. There is increasing recognition of the role played by small scale ocean processes in ocean-atmosphere coupling, upper-ocean mixing and ocean vertical transports, with advanced numerical models and in situ observations highlighting fundamental changes in dynamics when scales reach 1 km. Numerous scientific publications highlight the global impact of small oceanic scales on marine ecosystems, operational forecasts and long-term climate projections through strong ageostrophic circulations, large vertical ocean velocities and mixed layer re-stratification. Small-scale processes particularly dominate in coastal, shelf and polar seas where they mediate important exchanges between land, ocean, atmosphere and the cryosphere, e.g., freshwater, pollutants. As numerical models continue to evolve toward finer spatial resolution and increasingly complex coupled atmosphere-wave-ice-ocean systems, modern observing capability lags behind, unable to deliver the high-resolution synoptic measurements of total currents, wind vectors and waves needed to advance understanding, develop better parameterizations and improve model validations, forecasts and projections. SEASTAR is a satellite mission concept that proposes to directly address this critical observational gap with synoptic two-dimensional imaging of total ocean surface current vectors and wind vectors at 1 km resolution and coincident directional wave spectra. Based on major recent advances in squinted along-track Synthetic Aperture Radar interferometry, SEASTAR is an innovative, mature concept with unique demonstrated capabilities, seeking to proceed toward spaceborne implementation within Europe and beyond

ATMOSPHERIC CLIMATE CONTROL OF DIRECTIONAL WAVES IN THE UNITED KINGDOM AND IRELAND

International audienceUnderstanding multi-annual to decadal atmospheric climate controls on winter-wave climate is critical for coastal vulnerability assessment and future development of 'season ahead' forecasting of coastal risk. We examine the relationships between winter-average climate indices (NAO and WEPA) and directional wave power at 63 inshore locations throughout the United Kingdom and Ireland (UK&I). Analysis of hindcast wave data between 1980-2017 illustrate the extent of directional bi-modality, with 67% of inshore sites displaying directionally multimodal wave climates. Analysis of directional modes as a function of climatic indices illustrated the control exerted by NAO/WEPA on directional balance of inshore winter wave climate. Along Channel and southern North Sea coasts +WEPA significantly explains winter-averaged wave power for southwesterly wave directional modes (r = 0.58-0.77) and-NAO significantly explains variability in all easterly wave modes (r = 0.6-0.76), providing a mechanism for which 'season ahead' inshore wave climate forecasting and rotational beach response can be based

The recent storms and floods in the UK

This paper documents the record-breaking weather and flooding of winter 2013/14, considers the potential drivers and discusses whether climate change contributed to the severity of the weather and its impacts

CMEMS-Based coastal analyses: Conditioning, coupling and limits for applications

Recent advances in numerical modeling, satellite data, and coastal processes, together with the rapid evolution of CMEMS products and the increasing pressures on coastal zones, suggest the timeliness of extending such products toward the coast. The CEASELESS EU H2020 project combines Sentinel and in-situ data with high-resolution models to predict coastal hydrodynamics at a variety of scales, according to stakeholder requirements. These predictions explicitly introduce land discharges into coastal oceanography, addressing local conditioning, assimilation memory and anisotropic error metrics taking into account the limited size of coastal domains. This article presents and discusses the advances achieved by CEASELESS in exploring the performance of coastal models, considering model resolution and domain scales, and assessing error generation and propagation. The project has also evaluated how underlying model uncertainties can be treated to comply with stakeholder requirements for a variety of applications, from storm-induced risks to aquaculture, from renewable energy to water quality. This has led to the refinement of a set of demonstrative applications, supported by a software environment able to provide met-ocean data on demand. The article ends with some remarks on the scientific, technical and application limits for CMEMS-based coastal products and how these products may be used to drive the extension of CMEMS toward the coast, promoting a wider uptake of CMEMS-based predictions