• Flora Flora

    Climatic factors as a whole and the predominantly limy nature of the island´s soil condition the distribution of vegetation in the Tramuntana area and the altitude of plant communities. Their varied vegetation responds fundamentally to their climactic differences, since the higher parts are cold, windy and wet, whilst the lower parts are drier and warm [...]

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NATURAL LANDSCAPE

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The climate

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The main characteristic of the Mediterranean climate is none other than its summer droughts, since the hot period of the year coincides with a very low minimum rainfall, so the growth of vegetation is limited to a large extent by the scarcity of water in the soil. Thus by definition the Mediterranean climate is characterized by a shortage of summer rains leading to dry summers, and, on the island of Mallorca, this dry period peaks during the months of July and August, also preceded by a low rainfall in late spring.

Climatic factors play a decisive role in the Tramuntana area. The influence of large systems of depressions or low pressure originating in the Atlantic is not very important in Mallorca, whereas the influence of locally created aggravated disturbances are extremely important. The unique conditions of the basin formed by the Western Mediterranean, surrounded by high reliefs, make this area particularly prone to cyclogenesis, with the formation or reactivation of disturbances. This means that the Western Mediterranean is, in fact, the region in the northern hemisphere with most cyclogenetic activity in the cold season. The points where the formation of the centre of a depression is most probable are, in this order: the gulf of the Liguria-Tyrrhenian Sea, the gulf of Leon, the Catalan-Balearic Sea, the Algerian coast and the Alboran Sea. Peak rainfall in the month of October reflects the effectiveness of these Mediterranean disturbances.

In spite of the similarity in the rainfall pattern recorded by the island´s different meteorological observatories, the rainiest sectors can be identified as the central part of the Tramuntana Mountains, where there is a second peak in rainfall after the month of October, specifically, in December. In this case, it is assumed that orographic factors are influential during a period of the year when the general movement from the west reaches lower latitudes. Thus, occasionally there are moments of very heavy rainfall, with downpours producing over 300 mm in 24 hours. The recurrence of these downpours cannot be considered exceptional, so that within a period of 25 years one can expect maximums of over 250 mm in 24 hours in the central part of the mountain range.

In Mallorca, there is a big spatial variation in mean rainfall, with maximums situated around 1,200-1,400 mm a year in the central sector of the Tramuntana Mountains, whilst on the southern coast of the island it amounts to no more than 300-350 mm. This unsymmetrical pattern is basically due to orographic factors. Winds responsible for the heaviest precipitation (NE, N and to a lesser extent the SW winds) collide with the island´s reliefs, increasing the rainfall´s windward direction. Whilst the aforementioned orographic factor does determine the spatial distribution of rainfall, some studies of geographical rainfall distribution factors, using multivariate analysis techniques, point to the influence of factors such as the presence of mountain barriers in the direction of rainy winds, latitude, the concavity of the terrain, distance from the sea and irregularity of the reliefs. Thus latitude, for example, causes the coastal sector of Pollença – the northernmost part of the Tramuntana area – to be somewhat rainier (700-800 mm) than the southern section (500-600 mm). This is due, more than anything else, to the increase in summer rainfall in the north-eastern tip of the mountain range, and the fact that the Andratx area is sheltered from wet north-easterly winds.

Snowfall, on the other hand, is currently very unusual in the Balearic Islands, although the presence of snow on the summits of the Tramuntana Mountains once or several times a year is by no means strange to any islander. The highest number of recorded snowfalls corresponds to the central area of the mountain range, and at the observatory of the shrine at Lluc it is unusual for there to be none at all in any given year. This phenomenon occurs almost exclusively in the winter months, and the synoptic circumstances that lead to snow in Mallorca are the same ones that cause the coldest types of weather in the region, that is to say those usually linked to meridian advections with a northerly component, especially those from the NE, concentrated in the months of January, February and December, in order of frequency (highest to lowest).

As for temperatures, they follow the well-known pattern according to which annual minimums occur in the months of January and February, and maximums in July and August. Whilst most of the island of Mallorca has an annual average of 16º to 17º C, the Tramuntana area is singled out as the coldest area, with joint values below 16º C, and under 10º C at certain points in the central sector. This is determined by the uneven incidence of solar radiation and the orientation of its mountain slopes, meaning that its southern slopes enjoy a positive thermal anomaly with average annual temperatures of around 18º C. Thermal inversions and frosts are not infrequent in the Tramuntana area, above all in enclosed areas and the bottom of valley.