Comprehensive analysis of the climate variability in the eastern Mediterranean. Part I: map‐pattern classification

Abstract

Abstract:This paper provides an extended study of the dominant daily circulation patterns governing the climate variability in the eastern Mediterranean. The methodology adopted to determine the circulation patterns is based on combined analysis of the spatial and temporal variation of rotated principal components of sea-level pressure. A catalogue of characteristic seasonal composites is presented and discussed. It is found that, during winter and spring, large scale features situated in northern Europe affect the atmospheric circulation over the domain of study, whereas the Atlantic (Azores) anticyclone and the Asian Thermal Low define most of the observed circulation types in summer. In autumn, the area exhibits a rapid transition from the warm to cold season showing climatic features from both extreme seasons. Similarities between winter and spring/autumn patterns are detected and correlation analyses are employed between their spatial patterns to reveal that similar circulation patterns occur amongst the three seasons, which usually appear more pronounced during winter. Frequencies and trends of the proposed circulation types are examined for each season. A linear trend analysis for the overall period exhibits a significant increase in the anticyclonic types particularly in winter. With respect to the cyclonic types, statistically significant negative trends have been found in all seasons especially for types associated with depressional activity in central the Mediterranean.

Climatic features of atmospheric stability in the Mediterranean region (1948–2006): spatial modes, inter‐monthly and inter‐annual variability

“…The seasonal distribution of cluster 7 presents maxima in October and March (Figure 8(d)). The spring maximum is in agreement with the results of Kostopoulou and Jones (2007) regarding the frequency of an anticyclonic pattern similar to the 1000 hPa pattern of Figure 8(c). The inter-annual march of cluster 7 frequency (Figure 8(e)) does not present any considerable long-term changes during the period under study.…”

European CO budget and links with synoptic circulation based on GEOS-CHEM model simulations

“…In the present study, an automated map pattern classification is developed following the methodology by Kostopoulou and Jones (2007). The obtained circulation catalogue describes the main seasonal circulation types (CTs) over the NH at sea level pressure (SLP) and at selected levels (500 hPa, 200 hPa).…”

“…Finally, each day of the original data is assigned to one mode according to the absolute maximum component scores. The methodology adopted to determine the mappattern classification is described in greater depth in Kostopoulou and Jones (2007).…”

The sensitivity of warm period precipitation forecasts to various modifications of the Kain-Fritsch Convective Parameterization scheme

“…The choice of this period of the year is based on the fact that it is characterized in general by a weak synoptic-scale forcing, there is little influence from midlatitude systems and the convective activity is important over central and northern Greece (Flocas, 1993;Trigo et al, 2002;Kostopoulou and Jones, 2007;Mazarakis et al, 2008). For the statistical evaluation, the precipitation observations from 41 rain gauges operated by the Hellenic National Meteorological Service (HNMS), 26 rain gauges operated by the National Observatory of Athens, 13 rain gauges operated by the Ministry of Rural Development, 10 rain gauges operated by the National Technical University of Athens and 23 rain gauges provided by the ECMWF MARS data base are used.…”