Climate is average weather and its variability over a period of time, ranging from months to millions of years. The World Meteorological Organization standard is a 30-year average.
Because the atmosphere interacts with the underlying surface – oceans, land, and ice – the term climate system is used to encompass both the atmosphere and the influence of the Earth’s surface on climate.
The climate system consists of five elements: the atmosphere; the ocean; the biosphere; the cryosphere (ice and snow) and the geosphere (rock and soil).
Weather is always changing and the climate in different parts of the world is a combination of all the factors that affect the weather in any particular locality. In some regions of the world there are marked differences between summer and winter climates and here in the UK the climate is very changeable at all times of the year.
Many factors can affect the climate. These include:
- Distance from the equator
- Natural features
- Mountain regions
- Coastal regions
World climates can be divided into categories
This type of climate is predominantly dry. There are however, three distinct temperature ranges – hot, warm and cold.
Hot and dry climates are usually desert regions such as the Sahara and the Arabian. These hot deserts have little rain at any season and no real cold weather, although temperature drops sharply at night. Sand or rocks in direct sunlight will easily reach 60 °C to 70 °C (140 °F to 160 °F). But at night temperatures may drop to below freezing.
Warm and dry climates can be found in places that are semi-desert or dry grassland (tropical steppe) such as the Sahel region of Africa or the drier parts of India. In these regions, although there is a rainy season, the rains can fail several years in succession, causing severe drought.
Cold and dry climates can be found in the central parts of Asia, such as the Gobi desert. These cold deserts occur in higher latitudes in the interior of large continents and have a climate that is very hot in summer, but bitterly cold in winter.
Most equatorial and tropical parts of the earth have tropical climates characterised by high temperatures and high humidity throughout the year, and frequent rain throughout most of the year. This region can be split into two distinct types:
- Tropical wet – there is no distinct wet or dry season, rainfall is distributed throughout the year. This type of climate is characterised by lush tropical forests like the Amazon rain forest, central parts of Africa and Indonesia.
- Tropical wet and dry – there is a distinction between a wet and dry season. The wet season is usually influenced by monsoon winds that bring large quantities of moisture to a region. Countries like Bangladesh and the eastern side of India have this type of climate.
Temperate climate zones lie between the tropics and the polar circles. In these regions the changes between summer and winter are generally subtle – warm or cool rather than extreme; burning hot or freezing cold. However, a temperate climate can have very unpredictable weather. One day it may be sunny, the next it may be raining, and the next it may be cloudy. These erratic weather patterns occur in summer as well as winter.
Temperate climate zones can be split into two distinct types, depending on temperature:
- Warm temperate – can have rain all year with the wettest weather in summer months, with temperatures ranging from warm to hot all year. Eastern China and the south-eastern states of the USA, such as Florida, are good examples. Mediterranean areas also have a warm wet climate in the winter, but summers tend to be dry with little or no rainfall. Places around the Mediterranean, and some parts of central Chile, California and Western Australia have warm and dry temperate climates ideal for tourism and agriculture.
- Cold temperate – climates can be wet or dry. Cool and wet climates are places where there is rain every month, but no great extremes of temperature throughout the year. The climates of the British Isles, much of northwest Europe, New Zealand and coastal North America are of this type. The weather can be very changeable and strongly influenced by large moving weather systems called depressions or lows, and anticyclones or highs. Cold and dry climates are places where the weather is dominated by warm summers and cold winters. Regions such as central Europe are of this type.
Cold polar climate is subdivided into Tundra climate and Ice Cap climate. Tundra regions have very short often hot summers followed by bitterly cold and long winters (mean temperature of warmest month between 0 and 10°C). Areas of Canada, northern Russia and Siberia, extending to the Arctic are of this type.
Ice cap or polar climate is characterised by very low temperatures (mean temperature of warmest month below 0 °C), strong winds and year-round snow cover. This type of climate can be found on Greenland and at the Antarctic.
Mountain climate can be found in mountainous areas anywhere in the world, where land rises above permanent snowline, generally above 3000m in height. These areas often have cold winters and mild summers. Due to their elevation, temperatures are lower than you would expect for their latitude and the main form of precipitation is snow, often accompanied by strong winds. These areas can be found in the high mountainous areas such as the Andes in South America, the Himalayas and the Tibetan Plateau.
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