On the feasibility of the use of wind SAR to downscale waves on shallow water

O Q Gutiérrez,F Filipponi,P Camus,E Valentini,A Taramelli,F J Méndez

doi:10.5194/os-12-39-2016

Abstract

Abstract. In recent years, wave reanalyses have become popular as a powerful source of information for wave climate research and engineering applications. These wave reanalyses provide continuous time series of offshore wave parameters; nevertheless, in coastal areas or shallow water, waves are poorly described because spatial resolution is not detailed. By means of wave downscaling, it is possible to increase spatial resolution in high temporal coverage simulations, using forcing from wind and offshore wave databases. Meanwhile, the reanalysis wave databases are enough to describe the wave climate at the limit of simulations; wind reanalyses at an adequate spatial resolution to describe the wind structure near the coast are not frequently available. Remote sensing synthetic aperture radar (SAR) has the ability to detect sea surface signatures and estimate wind fields at high resolution (up to 300 m) and high frequency. In this work a wave downscaling is done on the northern Adriatic Sea, using a hybrid methodology and global wave and wind reanalysis as forcing. The wave fields produced were compared to wave fields produced with SAR winds that represent the two dominant wind regimes in the area: the bora (ENE direction) and sirocco (SE direction). Results show a good correlation between the waves forced with reanalysis wind and SAR wind. In addition, a validation of reanalysis is shown. This research demonstrates how Earth observation products, such as SAR wind fields, can be successfully up-taken into oceanographic modeling, producing similar downscaled wave fields when compared to waves forced with reanalysis wind.

Highlights

The synergic use of Earth observation (EO) products, wave reanalysis and in situ measurement can be adopted to provide scientific justifications for the appropriate selection of offshore wind farm location
A high similarity was found between the synthetic aperture radar (SAR) wind field and the reanalysis wind field; this suggests that there is a high persistence of wind direction during a time step of 1 h (Fig. 7)
Results show that SAR wind fields were able to solve fine-scale spatial patterns and improve wave downscaling in the study area, especially during bora wind events due to complex orography on the Istrian coast, the following weaknesses were found:

Summary

Introduction

The synergic use of Earth observation (EO) products, wave reanalysis and in situ measurement can be adopted to provide scientific justifications for the appropriate selection of offshore wind farm location. The level-2 SAR (synthetic aperture radar) products can help to better understand the wind fields in open-sea areas (Pieralice et al, 2014), while wave reanalysis and in situ monitoring could be integrated and calibrated using the satellite information. Wave reanalyses have become popular as a powerful source of information for wave climate research and engineering applications. These wave reanalyses provide continuous time series of offshore wave parameters; in coastal areas or shallow water, waves are poorly described because spatial resolution is not detailed (Camus et al, 2013).

Methods

Results

Conclusion