Chapter 4 Climate and Meteorology: variability and its influence on the Ocean José Ignacio Usabiaga a , Jon Sáenz Aguirre b , Victoriano Valencia c and Ángel Borja c a Instituto Nacional de Meteorología; Centro Meteorológico en el País Vasco; c/Caserío Parada, 48; 20015 San Sebastián b Departamento de Física Aplicada II; Facultad de Ciencias; Universidad del País Vasco; 48080 Bilbao c AZTI Foundation, Department of Oceanography and Marine Environment; Herrera Kaia, Portualdea s/n, 20110 Pasaia (Spain) 4.1. Introduction The area covered by this study is located in the easternmost part of the Cantabrian Coast; it extends over approximately 246 km of the littoral of the provinces of Bizkaia and Gipuzkoa (see Preface). In this area, the rivers flowing to the Cantabrian Sea drain a basin of about 4,500 km 2 , which extends over the provinces of Bizkaia, Gipuzkoa and parts of Araba and North-western Navarra (see Figures 1 and 2, in Preface). The rivers are short (about 40 km long), with pronounced slopes due to the orography of the region (Figure 4.1). The lower reaches of the main rivers flow almost perpendicular to the coast, from south to north, in northern Spain. Figure 4.1. (a) Main rivers discharging into the Cantabrian coast. (b) Topography of the area, obtained from the ETOPO2 (Smith and Sandwell, 1997) digital elevation model. The observation sites used in this study are shown in both parts of the Figure. For Key, see text. (a) (b)