Tropical climateTropical climate is the first of the five major climate groups in the Köppen climate classification identified with the letter A. Tropical climates are defined by a monthly average temperature of 18 °C (64.4 °F) or higher in the coolest month, and feature hot temperatures all year-round. Annual precipitation is often abundant in tropical climates, and shows a seasonal rhythm but may have seasonal dryness to varying degrees. There are normally only two seasons in tropical climates, a wet (rainy / monsoon) season and a dry season.
AridA region is arid when it severely lacks available water, to the extent of hindering or preventing the growth and development of plant and animal life. Regions with arid climates tend to lack vegetation and are called xeric or desertic. Most arid climates straddle the Equator; these regions include parts of Africa, Asia, South America, North America, and Australia. Aridification The distribution of aridity at any time is largely the result of the general circulation of the atmosphere.
Megadiverse countriesThe term megadiverse country refers to any one of a group of nations that harbor the majority of Earth's species and high numbers of endemic species. Conservation International identified 17 megadiverse countries in 1998. Many of them are located in, or partially in, tropical or subtropical regions. Megadiversity means exhibiting great biodiversity. The main criterion for megadiverse countries is endemism at the level of species, genera and families. A megadiverse country must have at least 5,000 species of endemic plants and must border marine ecosystems.
Geographical zoneThe five main latitude regions of Earth's surface comprise geographical zones, divided by the major circles of latitude. The differences between them relate to climate. They are as follows: The North Frigid Zone, between the North Pole at 90° N and the Arctic Circle at 66°33′48.7" N, covers 4.12% of Earth's surface. The North Temperate Zone, between the Arctic Circle at 66°33′48.7" N and the Tropic of Cancer at 23°26'11.3" N, covers 25.99% of Earth's surface. The Torrid Zone, between the Tropic of Cancer at 23°26'11.
