General Characteristics of Climate

Climatic Features of Europe. Europe is the only part of the world to lie almost entirely within the temperate zone. Only its northern coast and the islands of the Arctic Ocean are in the frigid zone.

The climate of Europe is greatly influenced by the Atlantic Ocean and the warm North Atlantic Drift Current in the northern part of that ocean. This current brings waters warmed by the rays of the tropical sun. The prevailing westerly winds carry with them the moist air of the Atlantic. These westerlies, or, to be more exact, north-westerlies in summer and south-westerlies in winter, penetrate deeply into the continent and moderate both the summer heat and winter cold. In summer they bring cool weather and rain-fall, in winter snow and thaw. The climate of Western Europe is mild. There are no sharp changes from cold to heat. Winters are warmer than in other parts of the world in the same latitudes. The severe frosts so characteristic of Asia and North America are rare visitors in these regions.
Further from the Atlantic, however, the weaker is its influence. In Eastern Europe the climate is more rigorous, temperature variations are sharper. These regions are reached by dry, continental winds from Asia and by cold winds blowing from the Arctic Ocean in winter and spring. The latter cause a sharp fall of temperature. Winters are longer and colder than in Western Europe, summers warmer and sunnier, rainfall is less (Fig. 27).
Isotherms. As a result of observations made over many years, scientists at meteorological stations are able to determine the monthly and yearly temperatures for various places on the globe. In order that the distribution of temperature over the earth's surface be depicted more clearly, temperature figures are put on the map and lines are drawn joining places of equal temperature. These lines on the map joining places of equal temperature are called isotherms. (Greek «isos»=equal, «thermos»=heat.) In most atlases, isothermal maps show the temperatures for January, the coldest month, and July, the warmest month, in the Northern Hemisphere. (In the Southern Hemisphere January is the warmest month, July the coldest.) In winter the land loses heat more rapidly than the water. The oceans, therefore, remain warmer than the neighboring continents. Hence the January isotherms on the Atlantic and Arctic Oceans bend toward the north and north-east, following the course of the warm current. On the land, on the other hand, these isotherms bend toward the south and south-east. On the climate map of Europe, the January isotherm of 0°C runs north-east from the southern coast of Iceland until it reaches the Arctic Ocean. It then bends sharply southward along the coast of the Scandinavian Peninsula and makes for the Alps. Skirting these on the south, it crosses the Balkan and finally the Crimean Peninsulas. In all these regions, despite the difference in latitude, the average January temperature is 0°C. South and west of this isotherm, mountainous regions excepted, winters are warm, the average temperature being above 0°C. North and east of this isotherm, winters are cold, the average temperature being below freezing-point. In summer the land heats more rapidly than the sea in similar latitudes. During this season the interiors of the continents are warmer than the neighbouring oceans. Hence the July isotherms in Europe curve slightly to the north-east as they move away from the Atlantic Ocean. On the climate map, the July isotherm of 20°C passes along the eastern and northern coasts of the Iberian Peninsula. Turning east it skirts the Alps, the Balkan Mountains and the Carpathians on the south. It crosses latitude 50°N at the Dnieper and finally reaches latitude 55°N on the Volga. South of this isotherm, summers are hot, mountainous regions excepted. To the north, summers are moderately warm.

Rainfall. The rainfall of Europe is dependent on the distance from the Atlantic, the prevailing winds and the relief. Rains are heaviest on the western slopes of the mountains facing the Atlantic Ocean (2,000 mm a year and over). As the warm, moist air of the ocean is forced up the mountains, it loses much of its heat. As a result of this cooling, some of the moisture condenses, falling as rain. The further the distance from the Atlantic, the lighter is the rainfall. It is least in the south-easternmost areas (about 200 mm off the northern coast of the Caspian). On the whole, however, Europe receives sufficient rain except in the south-east, which accounts for the absence of large deserts in this part of the world.