Precipitation in peninsular Spain: Influence of teleconnection indices and spatial regionalisation

Abstract

Precipitation constitutes a particularly variable climatic element in Spain. Study of teleconnection indices, closely related to precipitation, enables us to establish to a greater or lesser degree the mechanisms regulating pluviometric variability; these are vital for planning and managing water resources in semiarid regions. In the present article we attempt to identify the low-frequency patterns that present the closest statistical relationship with rainfall for each of the points on the MOPREDAS pluviometric data grid, covering the whole area of peninsular Spain. The results obtained reveal the clear dominance of Mediterranean Basin patterns, specifically of the Mediterranean Oscillation (MO) and of its version in the mid-levels of the troposphere (ULMO). Results, however, show a significant dominance of the Western Mediterranean Oscillation (WeMO) in the east of the Iberian Peninsula and the eastern part of the Cantabrian façade. Also noteworthy is the control exerted by the NAO over much of the centre and southwest of Spain, as well as the surprising dominance of an index that heretofore has not been used much, known as the Paris-London Westerly Index. Finally, we performed a regionalisation based upon the correlations between the teleconnection and precipitation indices by means of a principal components analysis, which revealed the existence of three differentiated pluviometric regions in peninsular Spain: Atlantic (centre and south), Mediterranean (east) and Cantabrian (north).

Characterisation of Extreme Precipitation Events in the Pyrenees: From the Local to the Synoptic Scale

“…WT6, with a depression to the northwest of the peninsula and an anticyclone in central Europe, favours a warm air advection from the south-southeast with a significant moisture content (Figure 5) that favors abundant precipitation in the eastern coastal area (Figure 7b), and also in the southernmost mountainous sector of the study area. This is one of the situations that is captured well by the negative phase of the WeMO (Figure 6), and it concisely explains the occurrence of torrential-type events in the extreme northeast of the Iberian Peninsula [49], and their pluviometric variability in general [51,58]. WT7 presents a high zonal gradi-ent that favours westerly flows over the Iberian Peninsula with a long-lasting advection over the ocean, which causes significant moist advection over the Atlantic façade; this exhibits a temporal frequency centred in the months of October, November and December (Figure S3).…”

Characterization of Extreme Precipitation Events in the Pyrenees. From the Local to the Synoptic Scale.

“…This is one of the situations that is captured well by the negative phase of the WeMO (Fig. 6), and it concisely explains the occurrence of torrential-type events in the extreme northeast of the Iberian Peninsula [47], and their pluviometric variability in general [49,56]. WT7 presents a high zonal gradient, which favours westerly flows over the Iberian Peninsula with a long ocean surface circulation, which causes significant moist advection over the Atlantic façade; this exhibits a temporal frequency centred in the months of October, November and December (Fig.…”

Relationship Between Atmospheric Teleconnections and the Northern Hemisphere's Circumpolar Vortex

“…The positive (negative) NAO is associated with positive (negative) temperatures departures in the eastern United States and northwestern Europe and negative‐ (positive‐) temperature anomalies in the Greenland/Labrador area (Wallace & Gutzler, 1981). PCA has been used to identify modes of variability associated with teleconnections including the NAO (e.g., Martinez‐Artigas et al., 2021).…”