Group A

Tropical climates

Hot all year. The seasons are wet and dry, not summer and winter.

A satellite view of the Amazon rainforest, dark green and dotted with small, even puffs of white cloud — Afternoon clouds over the Amazon rainforest, seen by a NASA satellite.Picture: NASA, Jeff Schmaltz, MODIS Rapid Response, Public domain, Commons

The tropical belt

Tropical (A) climates form a nearly unbroken belt around Earth, mostly within 15° of the equator. Encyclopaedia Britannica: Köppen climate classification Rule for A: the coolest month averages 18 °C or more. Encyclopaedia Britannica: Köppen climate classification

In the tropics the difference between day and night is usually bigger than the difference between the warmest and coolest months. Encyclopaedia Britannica: Köppen climate classification There, winter and summer mean little; wet and dry seasons set the rhythm of the year instead. Encyclopaedia Britannica: Köppen climate classification

On the Met Office’s world map, tropical climates sit in central Africa, central America and parts of Asia. Met Office: Climate zones

Tropical rainforest (Af)

Tropical rainforest climates are found in South America, Africa and South-east Asia, either side of the equator. Met Office: Climate zones In a tropical rainforest climate, average temperatures are usually around 20–30 °C, with little change through the year. Met Office: Climate zones

Every month gets over 60 mm of rain, which feeds thick rainforest and some of the richest wildlife on land. Met Office: Climate zones

Monsoon (Am)

Tropical monsoon climates have a season of heavy rain, linked to a seasonal change in wind direction. Met Office: Climate zones Am climates are found mainly in southern and south-eastern Asia. Encyclopaedia Britannica: tropical monsoon and trade-wind littoral climate

The Asian monsoon brings summer rain as warm, moist sea air moves inland towards low pressure north of the Himalayas. Encyclopaedia Britannica: tropical monsoon and trade-wind littoral climate

In a monsoon climate the hottest weather usually comes at the end of the short dry season. Encyclopaedia Britannica: tropical monsoon and trade-wind littoral climate

In the Americas and Africa, Am climates are of the trade-wind kind: moist trade winds rise up mountains along narrow coastal strips. Encyclopaedia Britannica: tropical monsoon and trade-wind littoral climate

Savanna (Aw)

Tropical savanna climates have a more marked dry season than monsoon areas, and grassland rather than rainforest. Met Office: Climate zones

In a tropical wet-dry (Aw) climate, the dry season gets longer the further you go from the equator. Encyclopaedia Britannica: tropical wet-dry climate Aw climates get about 50–175 cm of rain a year, mostly in heavy showers as warm air rises. Encyclopaedia Britannica: tropical wet-dry climate

The wet season comes when the rain belt near the equator, the intertropical convergence zone, moves overhead. Encyclopaedia Britannica: tropical wet-dry climate

Zebras grazing on short grass between scattered flat-topped acacia trees — Zebras among acacia trees in Serengeti National Park.Picture: Agness Abubakar Saidi, CC0, Commons

A savanna is open country with scattered trees over a continuous layer of grass, growing where it is hot and seasonally dry. Encyclopaedia Britannica: savanna The biggest savannas are in Africa, South America, Australia, India, the Myanmar–Thailand region and Madagascar. Encyclopaedia Britannica: savanna

Grasses, the main plants of savannas, appeared only about 50 million years ago. Encyclopaedia Britannica: savanna

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