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Coastal Iberia summertime low-level flow assessed from scatterometers
by Monteiro (IPMA, Portrugal), Vogelzang (KNMI),
In summer, the prevailing northerly flow off west Iberia occasionally intensifies and weakens with significant consequences for weather conditions and marine ecology in the region. The new generation of high-resolution wind products developed for the Advanced SCATterometer (ASCAT) at 6.25 km grid (ASCAT-6.25) was used to characterize wind maxima close to the major Iberian capes. Wind intensifications downwind Cape Finisterre are large and detached from the coast. It is hypothesized that it is the response to a large feature in the coastal morphology. Intensifications downwind Cape Roca and Cape São Vicente are smaller and closer to the coast. These are triggered by interaction of supercritical or transcritical flow with topography. ASCAT-6.25 evening and morning passes show two distinct regimes during intensification events: a southern regime with wind maximum moving towards the coast during the day and a northern regime in which this diurnal shift is not so clear. Another aspect that distinguishes these regimes is the later occurence of the wind maximum in the southern portion of the coast. ASCAT data also allow to identify wind relaxation events. These are followed by a poleward flow of warm water that interrupts the upwelling conditions over west Iberia south of 41ºN. This study was supplemented by non sun-synchronous RapidScat wind observations in the summers of 2015 and 2016 that allow a first glance of the wind at different phases of the diurnal cycle. RapidScat and ASCAT data confirm that wind intensifications are multi-day events, clearly distinct from the sea breeze circulation.
|Monteiro and Vogelzang, Coastal Iberia summertime low-level flow assessed from scatterometers |
accepted, J. Geophys. Res., 2018.Abstract (html) Complete text (pdf: 4 MB)