Latitude provides the location of a place north or south of the equator and is expressed by angular measurements ranging from 0° at the equator to 90° at the poles. Different latitudes on Earth receive different amounts of sunlight, and are a key factor in determining a region’s climate. For example, the higher the latitude of a given place (the farther away it is from the equator), the sharper the angle of the sun’s rays that reach it, meaning that the rays of the sun are spread across a broader area. Therefore, higher latitudes receive less heat than lower latitude areas nearer the equator.
The Earth’s axis is tilted 23.5° to the perpendicular, meaning that the amount of sunlight that a particular latitude receives changes with the seasons. From April to September, the Northern Hemisphere is tilted toward the Sun, where it receives more energy; the Southern Hemisphere receives this additional energy between October and March, when it is tilted toward the Sun.
Arctic
From 66.5N to the North Pole is the Arctic; from 66.5S to the South Pole is the Antarctic. Places within the arctic climate zones tend to be snow- or ice-covered year-round. This is despite the fact that they tend also to be exceptionally dry, sometimes receiving as little precipitation as the world’s driest deserts. Very little snow falls on these high-latitude regions, but even less melts due to the cold temperatures and scarce sunlight. The deep ice and snow that covers these regions has been built up over hundreds, indeed thousands, of years. In these regions, the Sun hovers above the horizon at midnight in the summer and never rises at all at times during the winter.
Temperate
The temperate zone is located between the arctic and tropic zones. However, ‘temperate climate’ is something of a misnomer since most regions located within the temperate climate zones experience distinct changes across four seasons. For example, in much of eastern North America – from the Ohio Valley in the United States to the southern shores of Hudson Bay in Canada – the ‘temperate’ climate can experience both arctic and tropical weather in the same year. These climate variations increase the further an area is from an ocean or another large body of water; they diminish in areas where oceans and other large bodies of water are able to influence the climate more strongly. Temperate regions are also affected by the direction of the air flow they receive. Areas in Canada, for example, have cool Arctic air passing through, while the southern United States receives warm air from the Gulf Stream.
Tropic
The tropical belt of land and sea extending around the globe on both sides of the equator – between 23.5S and 23.5N – receives the most sunlight, but it is not necessarily the hottest since it is covered extensively by oceans that use some solar energy for evaporation. This combination of high moisture and intensive solar heating results in a persistent zone of convection (the upward movement of moist, unstable air) known as a tropical low, which often results in generous cloud formation and frequent rainfall. These factors also help moderate the temperatures within this zone.
Most areas, however, are characterized by distinct sub-climates where average temperatures, precipitation, and other factors vary noticeably. Although there are different classifications of world climates, many of these sub-climates include low latitude tropical rainforest and tropical savanna; middle latitude maritime, mediterranean, and steppe; high latitude subarctic, tundra, and polar ice cap; as well as desert and highland areas.
