The intra-annual variation of precipitation amount and duration and their spatial distribution during the year are studied on a 10 day basis for the Greek region, using S-mode and T-mode factor analysis. (i) For the intra-annual variation of precipitation amount, two modes were revealed: the first shows one broad maximum during the conventional winter in stations affected by the sea; the second presents two maxima, the first during late autumn-early winter and the second during late spring, corresponding to the northern mainland stations. (ii) For the spatial distribution of precipitation, three main patterns were revealed: the first one is the 'winter' pattern, with the maximum over the west windward area; the second is the 'summer' pattern, with a maximum over the north inland region; and the third is the 'autumn' pattern, with the maximum over northwestern Greece. (iii) For precipitation duration, two types of intra-annual variation were revealed. The first one is similar to the first of the analysis for precipitation amount; the second presents two maxima, the first during the beginning of December and the second during the middle of February, corresponding to the areas of northwestern and northeastern Greece. (iv) For the spatial distribution of precipitation duration, three main patterns were revealed: the first is the 'summer' pattern, which is similar to the second of the analysis for precipitation amount; the second is the 'winter' pattern, with the spatial maximum located over the eastern mainland and western Crete; finally, the third one is the 'autumn' pattern, with the maximum in northwestern Greece. During the third 10 day period of October and the second 10 day period of February, precipitation seems to present singularities, possibly due to fluctuations in atmospheric circulation. The above intra-annual variations and spatial distribution patterns are connected to the seasonal variations of the depression trajectories, the atmospheric instability, the influence of sea-surface temperature as a cyclogenesis factor, and the windward or leeward character of the various areas (orographic effect).
Based upon sea-surface temperature (SST) data, recently corrected for bucket-intake observational change, the SST fluctuations since 1873 in the Mediterranean are studied and compared with air temperature (AT) fluctuations at some land stations of this area and for the Northern Hemisphere (ATNH). Instead of the actual temperature, we used the frequency difference (per cent) of the number of the warm minus cold months, ( fw -fc) annually and seasonally, smoothed using 10-year moving averages. This frequency difference was found to be a linear function of the actual temperature.For the whole Mediterranean, the trend of the SST is simple enough, with a minimum in about 1910 and a double maximum in about 1940 and 1965. A secondary minimum follows in 1975-1980, very strong in the eastern Mediterranean, with a rise after that to the present. This trend when compared with ATNH presents some differences: in the ATNH a minimum appears earlier, in 1890, but this is shown only slightly in the Mediterranean SST. The second SST maximum, in 1965, is not shown in ATNH, and the general rise of recent years starts in the ATNH about 10 years earlier.When considering the AT of the Mediterranean stations, it can be seen that the rise, after the minimum of 1910, stops 15 years earlier than the SST and ATNH. Then, an anomalous and slow decrease follows until about 1975-1980, followed by a rise to the present, which is delayed in the eastern Mediterranean.KEY WORDS Climatic change Mediterranean Air and sea-surface temperature
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.