Reliability of Extreme Significant Wave Height Estimation from Satellite Altimetry and In Situ Measurements in the Coastal Zone

Ben Timmermans,Christine Gommenginger,Andrew Shaw

doi:10.3390/jmse8121039

Ben Timmermans, Christine Gommenginger + Show 1 more

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https://doi.org/10.3390/jmse8121039

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Abstract

Measurements of significant wave height from satellite altimeter missions are finding increasing application in investigations of wave climate, sea state variability and trends, in particular as the means to mitigate the general sparsity of in situ measurements. However, many questions remain over the suitability of altimeter data for the representation of extreme sea states and applications in the coastal zone. In this paper, the limitations of altimeter data to estimate coastal Hs extremes (<10 km from shore) are investigated using the European Space Agency Sea State Climate Change Initiative L2P altimeter data v1.1 product recently released. This Sea State CCI product provides near complete global coverage and a continuous record of 28 years. It is used here together with in situ data from moored wave buoys at six sites around the coast of the United States. The limitations of estimating extreme values based on satellite data are quantified and linked to several factors including the impact of data corruption nearshore, the influence of coastline morphology and local wave climate dynamics, and the spatio-temporal sampling achieved by altimeters. The factors combine to lead to considerable underestimation of estimated Hs 10-yr return levels. Sensitivity to these factors is evaluated at specific sites, leading to recommendations about the use of satellite data to estimate extremes and their temporal evolution in coastal environments.

Highlights

Measurements of significant wave height (Hs) from satellite altimeter are finding increasing application in investigations of wave climate, variability and trends [1,2,3,4,5,6]
In this paper we explore these questions with the use of satellite altimeter Hs data in the European Space Agency (ESA) Sea State Climate Change Initiative (CCI) L2P product
Results suggest that the Sea State CCI L2P product generally gives a good representation of extreme Hs at distances of up to a few kilometers from the coast where it is limited primarily by low sampling of these events

Summary

Introduction

Measurements of significant wave height (Hs) from satellite altimeter are finding increasing application in investigations of wave climate, variability and trends [1,2,3,4,5,6]. The European Space Agency (ESA) Sea State Climate Change Initiative (CCI) project [6] recently released version 1.1 of their satellite altimeter data product, comprising both along-track 1 Hz measurements (Level 2P, L2P [7]) and multi-mission gridded maps of significant wave height (Level 4, L4 [8]) This carefully quality controlled and calibrated data product provides new opportunities to examine long-term variability of Hs across most of the globe. Research is further hampered by the fact that buoys may carry a range of instrumentation that responds differently to wave conditions— the extremes [13]—and whose operational maintenance is generally not driven by long term climatological considerations, suffering frequently from changes in instrument types, changing calibration practices and platform refits through their lifetimes [14] Noting these challenges, researchers find strong incentives in exploiting nearly 3 decades of remotely sensed data, that provide regular observations over much of the world’s oceans. Meucci et al [15] find that the heterogeneous assimilation rates of satellite observations into reanalyses can introduce spurious temporal wind speed and wave height trends

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