Influencia de los patrones de teleconexión del Atlántico Norte en la precipitación primaveral del Mediterráneo occidental.

Abstract

The influence of the North Atlantic teleconnection patterns of low-frequency variability over the springtime precipitation in the Western Mediterranean area is analysed. Singular value decomposition (SVD) of the springtime monthly mean fields for the paired 300 hPa geopotential height/precipitation has shown that their covariability is dominated by two main large-scale atmospheric circulation patterns. In SVD results, the first mode relates precipitation anomalies to the EA-Jet pattern. Above-normal rainfall anomalies are linked with a long-lived high-over-low blocking pattern characterised by split flow around a high located northward Britain Islands and a low over Iberia. The second covariability mode takes into account the response of the precipitation to the North Atlantic Oscillation (NAO) pattern. An enhanced spring NAO pattern is related to positive (negative) precipitation anomalies over the southern (northern) Western Mediterranean. Through these two modes, the North Atlantic large-scale atmospheric dynamics explains about 50% of the total spring precipitation variability in the Western Mediterranean area. The effectiveness of the western Mediterranean precipitation response to the teleconnection patterns is statistically assessed by using a Monte Carlo approach.