Translations of Encyclopedia about Geology

Climate Zones

Weather is the state of the atmosphere at a given moment in relation to wind, temperature, precipitation, and cloudiness. Observing the weather changes during a prolonged period of time yields mean values, permitting the classification of different climate zones. The regions of similar climate zones may be separated by great spatial distances.

Classification into individual climate zones helps describe and compare different ecosystems and landscapes. The climate depends first of all on the angle at which the earth is heated by the sun. For example, we know that around the equator the temperatures are high, whereas at the poles the temperatures are low. However, this does not mean that regions situated at the same latitude belong to the same climate zone. Although the angle of the sunlight may be the same, there are other important factors that have an impact on the climate.

In the interior, spring means fast warming and autumn a quick cooling. In contrast, the weather in coastal regions behaves differently. As a result of the higher rate of evaporation, it rains more often in the coastal regions than in the interior. The average temperature does not fluctuate, because the water has the capability of accumulating heat. In addition, cold or warm ocean currents also regulate the climate in those areas.

We classify the climate based on temperature, precipitation, evaporation, as well as on the vegetation growth. When we want to describe different kinds of climate, we usually follow the classification system proposed by W. Koppen. He divided the earth's climate into five main climate belts, then subdividing them into eleven main climates, in which the important factors are the precipitation, important dry seasons, and summer temperatures.

Along the equator is the tropical rainforest climate (humid and tropical, or monsoon climate). The mean temperature is 26 degrees Celsius. The climate is humid and is characterized by luxuriant vegetation and frequent, almost daily rainfall. In this climate, there are no seasons. In South America and in Africa, further away from the equator, the monsoon climate changes to savannah climate. The vegetation consists of savannah forests and grasses. Here, rainy season alternates with dry season. The average temperature oscillates between 23 and 27 degrees Celsius. The hottest temperatures occur before the beginning of the rainy season.

The climate in the transition zone between dry and parched regions is called the steppe climate. We find this type of climate in particular in North America (the prairies), in central Asia, North Africa, and Australia. Here, the vegetation is mostly grasslands and shrubs. The evaporation prevails over the precipitation.

In the desert climate, the vegetation becomes even more scarce. There are only a few places where some vegetation can grow. There is a considerable temperature fluctuation. It is not uncommon to have 50 degrees Celsius during the day, while at night the temperature drops to the freezing point. A large-scale desert climate is found in North Africa, and central and south Asia.

Central Europe and parts of the United States fall within the temperate, or mild climate belt. It is characterised by warm, dry summers and cool, moist winters. This zone is further subdivided into cool-mild and moist-mild climates. For example, in Germany predominates the vegetation of the latter. Precipitation occurs in all seasons. However, extreme temperatures are an exception.

Further north we find the always moist boreal forest climate. The mean annual temperature here is still over 10 degrees Celsius. The ground is covered by snow for many months. In the tundra climate region, where the mean annual temperature does not reach 10 degrees Celsius, the vegetation is rather modest. Trees do not grow in this region. Even further north, the temperatures stay below freezing. The infrequent precipitation occurs in the form of snow. In these latitudes, where the ground never thaws, there is no vegetation.

Different types of climate may be also determined by the marine influence. The continental climate is characterised by a considerable temperature oscillation during one day, as well as during one year. Precipitation is moderate, air humidity and cloudiness are negligible. Marine climate is characterised by mild temperatures and considerable amounts of precipitation and high humidity. Climate in higher altitudes, where the sunlight is stronger than in lower regions, is characterised by decreasing temperatures and air pressure in relation to the increasing altitudes.

In dry (arid) climate, where the amount of precipitation is lower than the rate of evaporation, there are only seasonal rivers. Running, year-round rivers are common in the moist (humid) climate, where the precipitation is higher than evaporation. Nival climate is characterised by a belt of permanent snow and ice. The evaporation is very low and precipitation occurs in the solid form (snow).

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