whole of the northern part of the continent. With the final melting
and disappearance of the ice-sheet, the topography of Europe
assumed nearly its present form, and man came upon the scene.
Minor changes, such as the separation of Great Britain from the
continent, may have occurred at a later date; but since the Glacial
period there have, apparently, been no fundamental modifications in
the configuration of Europe.
The elevation of each of the great mountain systems already described was accompanied by extensive eruptions of volcanic rocks, and the sequence appears to have been similar in every case. The volcanoes of the Mediterranean are the last survivors of the great eruptions which accompanied the elevation of the Alpine mountain system. (P. La.)
In western Europe by far the most prevalent wind is the S.W. or W.S.W. It represents 25% of the annual total; while the N. is only 6%, the N.E. 8, the E. 9, the S. 13, the W. 17 and the N.W. 11. Of the summer total it represents 22%, while the N. is 9, N.E. 8, E. 7, S.E. 7, W. 21 and N.W. 17. In Winds. south-eastern Europe, on the other hand, the prevailing winds are from the N. and E.—the E. having the preponderance in winter and autumn.[1] Of local winds the most remarkable are the föhn, in the Alps, distinguished for its warmth and dryness; the Rotenturm wind of Transylvania, which has similar characteristics; the bora of the Upper Adriatic, so noticeable for its violence; the mistral of southern France; the etesian winds of the Mediterranean; and the sirocco, which proves so destructive to the southern vegetation. Though it is only at comparatively rare intervals that the winds attain the development of a hurricane, the destruction of life and property which they occasion, both by sea and land, is in the aggregate of no small moment. About six or seven storms from the west pass over the continent every winter, usually appearing later in the southern districts, such as Switzerland or the Adriatic, than in the northern districts, as Scotland and Denmark.
The great determining factors of the climate of Europe are these. The northern borders of the continent are within the Arctic Circle; the most southern points of the mainland are 1312° or more north of the Tropic of Cancer; to the east extends for about 3000 m. the continuous land surface of Asia; to the west Climate. lie the waters of the north Atlantic, which penetrate in great inland seas to the north and south of the great European peninsula; the prevailing winds in western Europe as already stated are more or less south-westerly; and the arrangement of the highlands is such as to allow of the penetration of winds with a westerly element in their direction far to the east. The first two of these factors are not distinguishing influences. They affect the climate of Europe in the same manner as they do that of any other land surface in the same latitudes.
The remaining factors, however, are of the highest importance. It is to them in fact that Europe owes in a very large measure those physical conditions which are the basis of its recognition as a separate continent. In estimating the value of those factors one must bear in mind, first, that the waters of the north Atlantic are exceptionally warm, especially on the European side of the ocean. The Gulf Stream carries a large body of warm water northwards to near the parallel of 40° N., and to the north of the Gulf Stream prevailing south-westerly winds, especially during the winter months, drift onwards to the western and northern shores of Europe, even as far east as Spitsbergen, large bodies of water of an exceptionally high temperature. Secondly, one must bear in mind that these relatively high temperatures over the ocean promote evaporation and thus favour the presence of a relatively large amount of water-vapour in the air over those parts of the ocean which adjoin the continent; and, thirdly, that, as the winds are the sole means of carrying water-vapour from one part of the earth’s surface to the other, and the sole means of carrying heat and cold from the ocean to the land, the prevailing south-westerly winds are allowed by the superficial configuration to bring a relatively high rainfall and a relatively large amount of heat in winter to land farther in the interior than in any corresponding latitudes. During the summer the winds referred to have a cooling effect, but not to the same degree as those of winter tend to raise the temperature. From the point of view just indicated the only part of the world that is fairly comparable with Europe is the west of North America; but, as there the outline and superficial configuration are quite different, the oceanic influences affect only a narrow strip of seaboard and not any extent of land which could be regarded as of continental rank. It is owing to these influences that in the greater part of Europe there is a more or less continuous population dependent on agriculture. On the east side of Europe, again, the existence of the continent of Asia has a marked effect on the climate which also aids in giving to Europe its individual character. It is owing to that circumstance that the south-east of the continent, which has temperatures as favourable to agriculture as the corresponding latitudes of eastern Asia or eastern North America, is without the copious rains which make those temperatures so valuable, and hence forms part of the desert that divides the populations of Europe and Asia.
On the local distribution of rainfall and temperature, the physical configuration of the continent has very marked effects. Here as elsewhere there is a striking difference both in the amount of rainfall and the temperature on the weather and lee sides of mountains and even low hills. But with reference Precipitation. to this it should not be forgotten that water-vapour, heat and cold may be carried farther into the land by winds blowing in a different direction from that of those by which they were introduced from the ocean, and, with reference to rainfall, that the condensation of water-vapour may be brought out by different winds from those by which the water-vapour was brought to the area in which it is condensed. Water-vapour that may have been introduced by a south-westerly wind may be driven against a mountain side by a northerly or easterly wind, and thus cause rain on the northern or eastern side of the mountain. Still, any rainfall map of Europe indicates clearly enough the origin of the water-vapour to which the rainfall is due. Such a map, taking into account the results of more detailed investigations of different parts of the continent, is that of Joseph Reger.[2] This map shows the rainfall or rather total precipitation in seven tints at intervals of 250 mm. (about 10 in.) up to 1000 mm., and beyond that at intervals of 500 mm. up to 2000 mm. In some parts of the continent the limits of a rainfall of 200 mm. and 600 mm. are also shown. The picture there given is too complicated for brief description except by saying quite generally that it shows on the whole a diminution in the total amount of precipitation from west to east, and that the heaviest precipitation is indicated on the west or south and most exposed sides of mountains. The areas of scantiest rainfall lie to the north and north-west of the Caspian Sea and in the interior of the Kola Peninsula, north-west of the White Sea. The Stye in the English Lake District, some 2 m. from and 650 ft. higher than Seathwaite, has long been reputed to be the station recording the heaviest rainfall in Europe, but it has been shown to have a rival in Crkvice, a station immediately to the north of the Bocche di Cattaro on the Dalmatian coast. In the period 1881–1890 the average rainfall at the Stye amounted to 177 in., in 1891–1900 that at Crkvice amounted to about 179 in.[3]
The amount of the snowfall as distinguished from the rest of the precipitation is now coming to be recognized as an important climatological element. So far, however, the only European country in which a record of the snowfall is kept is Russia, but it may be pointed out that the scantiness of the Snowfall. winter precipitation and accordingly of snow in the south-east of Europe almost entirely prevents the cultivation of winter wheat, which is thus left without the protective blanket enjoyed in some other parts of the world with cold winters.
The important subject of the seasonal distribution of the rainfall
of Europe has received attention from Drs A. J. Herbertson, Köppen
and Supan, and Mr A. Angot. The rainfall of each month
in Europe as in the other continents is shown by Dr A. J.
Herbertson in The Distribution of Rainfall over the Land.[4]
Seasonal distribution
of rainfall.
On plate 19 of the Atlas of Meteorology, by J. G. Bartholomew
and A. J. Herbertson, Dr Köppen has furnished
maps showing the months of maximum rainfall and the seasons of
maximum and minimum rain frequency in different parts of Europe.
Mr A. Angot’s work on the subject is published in two papers in the
Annales du bureau central météor. de France, a series of memoirs in
which the rainfall observations of Europe for the thirty years 1861–1890
are recorded and discussed. The first paper (1893, B, pp.
157-194) deals with the Iberian Peninsula, the second (1895, B, pp.
155-192) with western Europe (from about 43° to 58° N. and as far
east as about 19° to 21° E.). Both papers are accompanied by maps
showing by six tints the mean rainfall for each month as well as for
the entire year; and that on western Europe, by maps extending
in the west as far south as Avila, the proportion of the rainfall
occurring during the winter, spring, autumn and summer months
respectively. But the most instructive maps on the subject embracing
the whole of Europe are four maps prepared by Dr Supan[5] to
show the percentage of the total rainfall of the year occurring in
spring, summer, autumn and winter respectively. From the maps it
appears that all the southern and western coasts of Europe have a
high proportion of rain in autumn, and that this is true also of the
whole of the Italian peninsula and the islands of the western half of
the Mediterranean, of all the south-west of the Balkan peninsula,
including the Peloponnesus, of the Saône-Rhone valley and both sides
of the Gulf of Bothnia, and that a high winter rainfall is characteristic
of Iceland, the extreme western coasts of Scotland, Ireland, France
and the Iberian peninsula, as well as of the greater part of the
Mediterranean region, but more particularly the south-east, while in
this region, and, again more particularly in the south-east, there is a
great scarcity of summer rains, which, on the other hand, form the
highest percentage in the interior and eastern parts of the continent.
If the year be divided into a winter and summer half, the area with a
predominance of summer rains begins in the east of Great Britain
- ↑ Vesselovski, as quoted by Voeikov, Die atmosphärische Circulation.
- ↑ Plate 1 in Petermanns Mitteilungen (1903).
- ↑ See a paper on “Das regenreichste Gebiet Europas,” by Prof. Kassner, Berlin, in Petermanns Mitteilungen (1904), p. 281.
- ↑ London, 1901 (one of the publications of the Royal Geog. Society).
- ↑ Plate 21 in Petermanns Mitteilungen (1900).
