Variability in the air–sea interaction patterns and timescales within the south-eastern Bay of Biscay, as observed by HF radar data

Abstract

Abstract. Two high-frequency (HF) radar stations were installed on the coast of the south-eastern Bay of Biscay in 2009, providing high spatial and temporal resolution and large spatial coverage of currents in the area for the first time. This has made it possible to quantitatively assess the air-sea interaction patterns and timescales for the period 2009-2010. The analysis was conducted using the Barnett-Preisendorfer approach to canonical correlation analysis (CCA) of reanalysis surface winds and HF radar-derived surface currents. The CCA yields two canonical patterns: the first windcurrent interaction pattern corresponds to the classical Ekman drift at the sea surface, whilst the second describes an anticyclonic/cyclonic surface circulation. The results obtained demonstrate that local winds play an important role in driving the upper water circulation. The wind-current interaction timescales are mainly related to diurnal breezes and synoptic variability. In particular, the breezes force diurnal currents in waters of the continental shelf and slope of the south-eastern 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.

Seasonal Variation of the Land Breeze System in the Southwestern Bay of Bengal and Its Influence on Air‐Sea Interactions

“…The direction of the current vector anomaly is approximately 90° left to the wind direction (Figures 9a–9c). Previous studies on the LBS, particularly on the north of 30°N, where the inertial period is less than a day, showed that the current modulation with respect to diurnal wind forcing is as expected from classical Ekman drift theory (Fontán et al., 2013; Rafiq et al., 2020) in which the current is directed to the right of the winds. In our case, the inertial period is ∼2 days at the buoy location, which is much longer than the diurnal time scale of the LBS wind forcing.…”

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

“…In addition, this study attempts to extend the results obtained by Fontán et al . [] by considering not only the influence of simultaneous winds on surface currents, but also the effect of the past wind conditions. Furthermore, the study focuses on the response of surface currents to wind in order to complement the results obtained by Fontán et al .…”

“…Furthermore, the study focuses on the response of surface currents to wind in order to complement the results obtained by Fontán et al . [] dealing only with low‐frequency wind‐induced currents. In particular, the main aims are to: (a) investigate the response of the ocean to the wind forcing on time scales of hours to 20 days, (b) examine the isotropic and anisotropic wind impulse response functions, and (c) determine spatial and seasonal variability in the transfer functions.…”

“…Based on those HF radar currents, Fontán et al . [] determined the simultaneous wind‐current interaction spatial patterns and time scales in the same region at low‐frequencies, without having to consider the past wind conditions. More recently, Solabarrieta et al .…”