Atmospheric patterns for heavy rain events in the Balearic Islands

Abstract. The Balearic Islands, as well as other Mediterranean regions, are occasionally affected by heavy rain events, which can produce numerous damages. This study contributes to improve the understanding of the dynamical mechanisms that produce heavy rain events by means of a classification of their related atmospheric patterns.

Heavy rainfall dataset for the Balearic Islands and some gridded atmospheric parameters, derived from the HIRLAM-INM-0.5° analyses, were the data used in this study. Heavy rain events were recorded at a set of pluviometric stations along the Balearics for a period of 9 years, from June 1995 to May 2004. The 1000 hPa and 500 hPa geopotential heights (hereafter φ₁₀₀₀ and φ₅₀₀), as well as the 850 hPa temperature (T₈₅₀) were the fields utilized in the classification.

By means of a principal components analysis (PCA) the number of variables was reduced. The cluster analysis (CA) was then applied on those new variables and eight atmospheric patterns were finally obtained. Most of the patterns showed a strong relationship between heavy rain events and cyclones.