Global climate patterns

The world is divided into a number of climatic zones - large areas that experience a similar pattern of temperature and precipitation. These zones form parallel bands at different latitudes. These large-scale ecosystems are called biomes.

The main biomes: tundra, taiga (coniferous forest), temperate deciduous forest, temperate grassland, chaparral or evergreen hardwood (mediterranean), desert, tropical rainforest, savanna grassland.The Earth's main biomes

Patterns of global temperature and rainfall are affected by:

  • Latitude - higher temperatures are recorded closer to the equator, while lower temperatures are recorded towards polar latitudes. In between, there is a gradual decline in temperature due to reduced insolation - the sun is strongest at the equator and weakest at the poles.
  • Continentality - during summer, the sea heats up less quickly than the land. During winter, the opposite happens, and the sea retains heat from the sun longer than the land. Places close to the sea have slightly cooler summers, milder winters, and higher rainfall than places inland.
  • Altitude - temperatures decline as height above sea level increases. The actual rate of temperature loss is around one degree Celsius for every 150 metres of height. This is because the air gets thinner in higher altitudes. High areas also receive more rainfall and snowfall.
  • Global air circulation - this is the large-scale movement of air that helps redistribute energy across the surface of the Earth. Air is warmed near the equator, rises, and then spreads towards the poles where it cools down. It then flows back towards the equator, and the process repeats itself. The process is complicated by the rotation of the Earth which creates the Coriolis effect, which deflects the north-flowing air to the right in the northern hemisphere and to the left in the southern hemisphere.
  • Prevailing winds - some prevailing winds blow over land, while others blow over the sea. This affects the temperatures at particular locations.
  • Ocean currents - along with circulating air currents, ocean currents also help to redistribute energy across the planet. Oceans hold on to heat from the sun longer than areas of land and currents move this heat around from around the equator to the higher latitudes. Ocean currents run in giant loops (or gyres) in the major oceans in both hemispheres, and currents flowing away from the equator are called warm currents, while those flowing towards the equator are called cold currents. Both warm and cold ocean currents can affect temperatures of places close to the sea. For example, the Labrador Ocean current consists of cold water which flows southwards from Greenland towards Canada, reducing temperatures of coastal areas.