Regional and local scale atmospheric forcing upon sea level along the coast of SW Europe

Abstract

Sea level height variability along the coast of southwestern Europe is analyzed in relation with local and regional scale atmospheric forcing mechanisms. A circulation type (CP) catalogue, derived from a combination of principal component analysis and cluster analysis was used to characterize the regional scale atmospheric circulation, whereas the local scale was highlighted through the analysis of hourly wind records during extreme events. A large portion of common anomalous sea level variability at 6‐hourly time frame can be explained by the effect of one CP, depicting a deep extra‐tropical disturbance, close to the Iberian Peninsula, which represents the dominance of the inverse barometer mechanism. Other CPs can induce occasionally similar effects, but showing a spatially restricted scope, in relationship with the location of the main centres of action. Embedded into this synoptic framework, a local forcing, related to both meteorological processes (wind set up) and coastal oceanographic features (depth of the continental shelf) usually control the timing and less frequently, the magnitude of the surges. The decreasing trend observed in the magnitude of the sea level residuals derived from a hindcast model as well as some spatial differences (more intense trend in the upper percentiles along the northern Spain and Mediterranean coasts) can also be explained by long‐term changes in the frequency, and specially, in the internal variability of the CPs, which might be linked to the recent positive phase and eastward displacement of the southern node of the North Atlantic Oscillation. An overall increase in sea level pressure, detected in all CPs, has been accompanied by significant increases in types characterized by anticyclones over the Iberian Peninsula and decreases of northerly flows, related to a reduction of the number of cyclones passing through the Gulf of Biscay and the Western Mediterranean Basin.

Characterization of surface winds over the Iberian Peninsula

“…The wind database presents two main drawbacks that could affect the conclusions presented above. First, the length of the analysed period, 6 years, could be considered insufficient to characterize the wind climatology, as a decadal variability of the large‐scale circulation in the IP has been demonstrated in several works (Jerez et al , ; Kirchner‐Bossi et al , ; Rasilla‐Álvarez and García‐Codrón, ). This issue will be assessed in a forthcoming paper using a long regional climate simulation.…”

“…A better knowledge of wind behaviour could benefit multiple sectors, such as the insurance and wind power industries (Changnon et al , ; Jerez and Trigo, ; Jerez et al , ). The study of forest and infrastructure damage (Jungo et al , ), coastal erosion (Costas et al , ), storm surges (Bijl, ), sea‐level variability (Rasilla‐Álvarez and García‐Codrón, ), aerosol and pollutant transport (Darby, ; Beaver and Palazoglu, ) and up‐welling/down‐welling (McClain et al , ; Herrera et al , ), among others, would also benefit. In particular, improvements in wind resource estimations would be relevant for generating power (Palutikof et al , ; Pryor et al , ; García‐Bustamante et al , ; Jerez and Trigo, ), allowing a more accurate identification of suitable locations for wind farms and helping to reduce uncertainty in wind power predictions (Costa et al , ).…”

“…These classifications are usually named circulation types (CTs). Traditionally, CTs have been used to analyse the regional climatic variability of elements such as precipitation (Romero et al , ), temperature (Cassou et al , ; Philipp et al , ; Yiou et al , ; Bermejo and Ancell, ), sea‐level variability (Rasilla‐Álvarez and García‐Codrón, ) and wind (Kaas et al , ; Soriano et al, ; Jiménez et al , ; Martín et al , ). CTs facilitate the assessment of how large‐scale circulation influences wind variability at regional scales, which can vary substantially between nearby areas as a simple response to the orography or land properties (Simpson, ; Bianco et al , ).…”

Synoptic‐climatological evaluation of the classifications of atmospheric circulation patterns over Europe

“…Kostopoulou and Jones, 2007;Nishiyama et al, 2007;Lorenzo et al, 2008;Jones and Lister, 2009;Schuenemann et al, 2009;Casado et al, 2010;Tveito, 2010;Brisson et al, 2011;Küttel et al, 2011;Raziei et al, 2012 to name just a few recent examples) including extremes (Cassano et al, 2006;Jacobeit et al, 2009;Maraun et al, 2011) and diurnal cycles (Twardosz, 2010). Many other climatic and environmental characteristics have, nevertheless, been investigated as well: wind and wind storms (Cassano et al, 2006;Leckebusch et al, 2008;Donat et al, 2010), droughts (Vicente-Serrano and López-Moreno, 2006;Fleig et al, 2010), floods (Dayan et al, 2012), snowfall and avalanches (Esteban et al, 2005;Bednorz, 2008;García et al, 2009), lightning activity (Pineda et al, 2010), atmospheric pollutants and dust transport (Demuzere et al, 2009Lykoudis et al, 2010;Stefan et al, 2010;Dayan et al, 2012;Gaetani et al, 2016;Beck et al, 2014), forest fires (Kassomenos, 2010;Rasilla et al, 2010), storm surges (Ullmann and Monbaliu, 2010;Rasilla and García-Codrón, 2016), potato yields (Sepp and Saue, 2012) and many others.…”

Circulation‐type classifications in Europe: results of the COST 733 Action

“…An application of circulation classifications from cost733cat to a specific environmental problem of wild fires is provided by Trigo et al (). Gaetani et al () analyse the effect of atmospheric circulation on dust transport on the basis of their own implementation of two classification methods using classification software cost733class, whereas Rasilla Álvarez and García‐Codrón () apply one classification method to study effects of atmospheric circulation on the sea level along the Iberian coast.…”