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CR 23:247-261 (2003)  -  doi:10.3354/cr023247

Role of orography in the spatial distribution of precipitation over the Spanish Mediterranean zone

M. G. Sotillo1,*, C. Ramis1, R. Romero1, S. Alonso1,2, V. Homar1

1Meteorology Group, Departament de Física, Universitat de les Illes Balears, 07071 Palma de Mallorca, Spain
2Institute Mediterrani d¹Estudis Avançats (IMEDEA), Universitat de les Illes Balears - Consejo Superior de Investigaciones Científicas (UIB-CSIC), 07071 Palma de Mallorca, Spain

ABSTRACT: The effects of orography on the precipitation field in the Spanish Mediterranean zone are studied through numerical simulations from a climatological point of view. The main atmospheric patterns that produce significant precipitation in the considered area, derived in a previous study, have been used as input data. The numerical simulations have been performed using the HIRLAM model. We isolate, by means of a factor-separation technique, the separate effects of the Iberian and non-Iberian orographies, as well as the synergy between the 2 orographies. The diversity of simulated-precipitation spatial distributions is clearly linked to the wide variety of flows over the Iberian Peninsula. However, a clear distinction between Atlantic and western Mediterranean disturbances is obtained. When Atlantic westerlies occur over the Iberian Peninsula, rainfall in the Spanish Mediterranean zone is enhanced by orography, mainly by that of Iberia. Otherwise, when the Iberian Peninsula is affected by Mediterranean disturbances, local orographic enhancements along with the redistribution of precipitation due to non-Iberian orography and synergistic effects are observed. The North African Atlas range, due to its primary influence, emerges as one of the factors governing the spatial distribution of rainfall across the Spanish Mediterranean zone.

KEY WORDS: Western Mediterranean · Precipitation · Numerical simulation · Orographic effects · Factor separation

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