Variability in the air–sea interaction patterns and time-scales within the Southeastern Bay of Biscay, as observed by HF radar data

Abstract

Two high frequency (HF) radar stations were installed on the Southeastern Bay of Biscay in 2009, providing high spatial and temporal resolution and large spatial coverage currents for the first time in the area. This has enabled to determine quantitatively the air–sea interaction patterns and time-scales for the period 2009–2010. The analysis was conducted by using the Barnett-Preisendorfer approach to canonical correlation analysis (CCA) of reanalysis surface winds and HF radar-derived currents. The results reveal that the CCA yields two canonical patterns. The first wind-current interaction pattern corresponds to the classical Ekman drift at sea surface, whilst the second describes an anticyclonic/cyclonic surface circulation. The results obtained demonstrate that the local winds play an important role in driving the upper water circulation. The wind-current interaction time-scales are mainly related to diurnal breezes and synoptic variability. In particular, the breezes force diurnal currents in the continental shelf and slope of the Southeastern Bay. It is concluded that the breezes may force diurnal currents over considerably wider areas than that covered by the HF radar, considering that the northern and southern continental shelves of the Bay exhibit stronger diurnal than annual wind amplitudes

Surface water circulation patterns in the southeastern Bay of Biscay: New evidences from HF radar data

“…Vertically, the good agreement between Figure 5(a) and Ferret and Cap Breton canyons, has been studied by several authors (Pingree and Le Cann, 1992;García-Soto et al 2002;Serpete et al, 2006;Caballero et al, 2008;and Caballero et al, submitted), who relate eddy generation to the interactions of the slope current with the complex bathymetry. Further, recent research relates the presence of an anticyclonic surface circulation in the area, to the influence of NE winds (more frequent in summer); likewise, a cyclonic surface circulation to SW winds in winter (Fontán et al, 2013). Further research is needed: (a) to understand the physical mechanisms driving these circulation patterns; and (b) to evaluate their contribution to the total variance of the regional.…”

Anisotropic response of surface circulation to wind forcing, as inferred from high‐frequency radar currents in the southeastern Bay of Biscay

“…The data from CFSV2 can be considered identical to CFSR (Climate Forecast System Reanalysis), except for the spatial resolution which increases from approximately 0.3° to 0.2°. Fontán [] validated the reanalysis winds (CFSR), for the period 2002–2010, by comparison with the wind observations from deep‐sea buoys in the region. The reanalysis winds show good agreement with the observational data, with correlation coefficients of 0.86 ± 0.10, root‐mean‐square differences of 1.21 ± 0.09 m s −1 and mean absolute errors of 0.44 ± 0.05 m s −1 .…”