Modeling of Gaseous Photochemical Pollution and Particulate Matter in the Western Mediterranean Basin (spanish Levantine Coast) by Using High-resolution

The high levels of photochemical pollutants in the entire Western Mediterranean Basin (WMB), and, specially, in the Spanish Levantine coast, present a high impact on ecosystems and human health, exceeding thresholds established in European Directives (Millán et al., 2000). This area is critically sensitive to photochemical pollution, due to its complex topography, which induces a complicated structure of the flow with important effects in the transport and transformation of air pollutants (Jiménez and Baldasano, 2004). The WMB is surrounded by high coastal mountains and in summer becomes isolated from the traveling lows and their frontal systems, which affect the weather at higher latitudes. The meteorology and the origin of the air masses arriving at the Iberian Peninsula are highly influenced by the Azores high-pressure system, which is located over the Atlantic Ocean and that intensifies during the warm season inducing very weak pressure gradient conditions all over the region (Lelieveld et al., 2002). The canalization between the Pyrenees and the French Central Massif introduced northwestern flows into the Mediterranean. This canalization plays an important role, because it is the only pass bringing fresh air into the WMB (Gangoiti et al., 2001). This work analyzes the levels of particulate matter in a domain of 216x314 km, located in the Spanish Eastern Levantine (WMB), during 13-16 August 2000.