LARGE-SCALE CIRCULATION REGIMES AND SURFACE CLIMATIC ANOMALIES OVER THE MEDITERRANEAN

Significant relationships between atmospheric circulation anomalies, in terms of monthly mean 500 hPa geopotential height (Z(500)) and sea-level pressure (SLP) over Atlantic-Europe, and surface climatic anomalies, in terms of monthly rainfall (R(m)) and monthly mean temperature (T-m), over the extended Mediterranean area, are examined statistically by canonical correlation analysis (CCA), with time lags from zero to four months. At a confidence level of 99.99 per cent, CCA yields five pairs of patterns that describe simultaneous responses of the monthly rainfall field to anomalies of surface circulation (SLP). Between mid-tropospheric circulation (Z(500)) and rainfall fields, six concurrent CCA pairs were also identified to be significant at the same confidence level. From the synoptic point view, these results seem very reasonable. Six concurrent (hereafter lag 0) CCA pairs and one CCA pair for a lag of 1 month (hereafter lag 1) were identified for the Z(500)-T-m fields at the confidence level of 99 per cent. The SLP-T-m fields, also six concurrent CCA pairs and three pairs for lag 1, were found to be significant at the same confidence level. Quite similar temperature anomaly patterns are represented in the first CCA pairs of the Z(500)-T-m fields for both lag 0 and lag 1, and in the first lag-1 and second lag-0 CCA pairs of the SLP-T-m fields; the patterns of air temperature anomalies revealed in the third CCA pair of SLP-T-m fields for lag 1, as well as in the fourth concurrent CCA pairs of the Z(500)-T-m and SLP-T-m fields, also resemble each other. Similar temperature anomaly patterns can be found for other CCA pairs. These similarities reveal that some slow-changing processes in large-scale anomalies of atmosphere are responsible for producing the same type of temperature anomalies.