Each world climate zone is broadly based on the tropics of Cancer and Capricorn, and the Arctic and Antarctic circles. This broad classification has also been subdivided into maritime and continental zones, as there are often significant weather differences between coastal and inland areas. Mountain ranges and ocean currents also have a profound effect on the local weather conditions.
Difference Between Weather and Climate
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Both weather and climate comprise similar factors, but weather is local and variable, while climate refers to long-term average weather patterns of a region.
Climate Zones
German climatologist Wladimir Koeppen (1846-1940) devised a system to classify climate zones that is still widely used. He divided Earth’s climate into five broad categories, designated A through E. A sixth category, H, was later added. The Koeppen climate classification is further subdivided according to criteria such as temperature and precipitation, for a total of 24 different climate zones.
- A, Humid Tropical is warm year-round, with average temperatures above 18 degrees C (64 degrees F). This climate zone lies near the equator, mainly between the Tropic of Capricorn and the Tropic of Cancer.
- B, Dry includes steppe and desert areas, where the rate of evaporation is greater than the amount of precipitation.
- C, Mild Middle-latitude consists of Mediterranean and coastal areas with dry summers and mild winters.
- D, Severe Middle-latitude is mainly found in the continental regions of North America and Eurasia, with long, bitterly cold winters. This category also includes the sub-arctic region.
- E, Polar consists of arctic tundra and polar ice caps, where temperatures never exceed 10 degrees C (50 degrees F).
- H, Highland refers to high elevation areas whose climate is colder and often wetter than adjacent, low-elevation areas.
While the characteristic weather patterns of each climate zone generally remain constant from year to year, the different zones can experience wide variations in weather, which may change on a daily basis.
Tropical & Subtropical Global Climate Zone
Tropical – Weather in tropical zones usually has long periods of high rainfall with a short dry season. Temperature and humidity are consistently high. The day length hardly changes throughout the year and the weather stays very warm, even at night. The Tropical climate zone mostly occurs between the Tropic of Cancer and the Tropic of Capricorn.
Subtropical – The wet and dry seasons are of similar length with a broad range of temperatures recorded. The subtropical world climate zones are generally north and south of the tropical regions near the Equator.
Arid & Semi-arid Global Weather
Arid – Low rainfall with large temperature ranges between night and day, as well as winter and summer. Evaporation exceeds rainfall, creating desert regions. Strong and frequent winds in this climate zone also add to the dry weather conditions.
Semi-arid – Higher rainfall and lesser temperature fluctuations than arid regions. These regions often experience severe droughts, are flat, and are exposed to very windy conditions.
Temperate & Northern Temperate Weather
Temperate – Global climate temperate zones have four distinct seasons with warm summers and cold winters, uniform rainfall patterns and snowfalls.
Northern Temperate – Similar to Temperate regions but with longer winters and higher snowfalls. Winter may be up to nine months with very cold, harsh weather.
Other World Climate Zones
Mountain – Global weather in the mountain zones has regular snowfalls with rainfall depending on local rain-bearing winds. Temperatures are much lower than low-level regions which are at similar latitudes. Mountain climates tend to be windy.
Polar – Frequent snow with long, cold winters and only slightly warmer summers. These regions occur on the North and South Poles and are subjected to long periods of light and darkness, depending on the season. Frozen oceans often occur in these global climate zones.
Coastal – Local weather often depends on the sea-surface temperature. The temperature ranges are narrower than nearby inland areas. Coastal world climate regions are often subjected to cooling sea breezes, fog, and winds that carry salt spray.
Mediterranean – Summers are hot and dry with cool, wet winters. Mediterranean climate zones mostly occur on coasts, causing higher rainfalls in the winter months.
Global weather varies greatly and within each climate zone temperatures and conditions may also have large differences. The formation of the land, altitude, and distance from the Equator are a few factors that affect global climate and local weather.
Factors that Determine Weather
The key elements affecting weather are temperature, humidity and air pressure, all of which are influenced by the uneven heating of Earth’s surface by the sun.
Temperature is largely determined by the amount of solar energy in the atmosphere in a given location. This varies according to the number of hours of sunlight received per day and the angle at which it strikes Earth. Other factors affecting temperature are reflection and scattering of sunlight, cloud cover, absorption by gases in the atmosphere, and conditions on Earth’s surface.
Solar energy drives the water cycle and affects the amount of humidity in the atmosphere. Water on the ground evaporates and rises into the atmosphere as water vapor. Under the right conditions, it condenses into clouds and returns to Earth as precipitation.
Air pressure is also affected by solar heating. Differences in air pressure cause local winds when air flows from high pressure to low pressure areas. An air mass is a large body of air that has a uniform temperature and humidity. Since cool, dry air is denser than warm, moist air, a cold air mass will move under a warm air mass and push it up. As the warm, humid air rises, it condenses and forms clouds, resulting in precipitation. The boundary between two air masses is called a front, named after the battle lines where opposing armies clashed during World War I.
Factors that Determine Climate
Climate is comparatively constant because it is largely determined by an area’s latitude, the distance above or below the equator. Due to the 23.5 degree tilt of Earth’s axis relative to the sun, the equator receives more direct sunlight than anywhere else on Earth. Therefore, the equator has the highest year-round average temperature, while the poles, which receive the least amount of sunlight, have the lowest average temperature. Other factors affecting climate include altitude, mountain ranges and proximity to large bodies of water.
Reference:
Burroughs, William J., et al., An Australian Geographic Guide to Weather, Australian Geographic Pty Ltd, Australia, 2000
