What a Aw climate is like
Aw Tropical savannah. Warm throughout, with a wet season and a distinct dry season long and dry enough for grassland and scattered trees rather than closed forest.
The rules behind the code, in plain English:
- Tropical (coldest month 18 °C or more).
- Not a rainforest or monsoon: the driest month gets under 100 minus yearly rainfall divided by 25 (in mm).
Dataset wording: "Tropical, savannah". In the maps of Beck et al. (2023) the class is written: A: Not B and Tcold >= 18; w: Not Af and Pdry < 100 - MAP/25.
Tropical savannah climate is hot all year, with a clear wet season and a clear dry season. The landscape swings from green to brown: open grassland with scattered trees, which burn or wither in the dry months and surge back with the rains. Farmers grow sorghum, maize, cotton and groundnuts, and herding is common. People dress for heat and dust in the dry season and for downpours in the wet one.
How much of the world is Aw?
- 13%of the world's land outside Antarctica, 1991 to 2020
- 17,895,072 km²area, 1991 to 2020
- 5,841cities of 15,000 or more people (GeoNames) have this climate now
In 1901 to 1930 it covered 12% of that land, so its area then was 7.42% smaller than in 1991 to 2020.
How the Aw area is projected to change by 2071 to 2099
These figures compare the area of Aw in each future map with 1991 to 2020. They come from the Beck et al. (2023) model projections under three emissions scenarios. They show what the scenarios imply, not what will happen.
| Map | Share of land | Change in area vs 1991 to 2020 |
|---|---|---|
| 1901 to 1930 (past) | 12% | -7.42% |
| 1991 to 2020 (now) | 13% | - |
| 2071 to 2099, SSP1-2.6 (low emissions) | 14% | +6.46% |
| 2071 to 2099, SSP2-4.5 (middle of the road) | 15% | +12.1% |
| 2071 to 2099, SSP5-8.5 (high emissions) | 16% | +17.13% |
Shares are of land outside Antarctica. A negative change means the zone shrinks.
What happens to today's Aw land
Of the land that is Aw in 1991 to 2020, this is how much stays Aw and where the rest ends up in 2071 to 2099, by scenario:
| Scenario (2071 to 2099) | Stays Aw | Where the rest goes (biggest first) |
|---|---|---|
| SSP1-2.6, low emissions | 96% | BSh (2.4%), Am (1.2%) |
| SSP2-4.5, middle of the road | 95% | BSh (3.1%), Am (1.4%) |
| SSP5-8.5, high emissions | 93% | BSh (4.7%), Am (2%) |
Looking back, 89% of today's Aw land was also Aw in 1901 to 1930. The rest was Am (3.9%), Cwa (3.4%), BSh (2.4%), Cwb (0.7%).
Where Aw is found
The countries with the most Aw land in 1991 to 2020:
| Country | Area | Share of all Aw | Share of the country |
|---|---|---|---|
| Brazil | 4,092,973 km² | 23% | 48% |
| Democratic Republic of the Congo | 1,297,748 km² | 7.3% | 56% |
| India | 1,069,845 km² | 6% | 34% |
| Australia | 788,346 km² | 4.4% | 10% |
| Tanzania | 706,185 km² | 4% | 75% |
| Angola | 660,559 km² | 3.7% | 53% |
| Nigeria | 639,787 km² | 3.6% | 70% |
| Central African Republic | 603,914 km² | 3.4% | 97% |
Places with a Aw climate today
The biggest cities in the 1991 to 2020 map that sit in Aw (at most two per country):
- Kinshasa, Democratic Republic of the Congo
- Lagos, Nigeria
- Ho Chi Minh City, Vietnam
- Bengaluru, India
- Hyderabad, India
- Rio de Janeiro, Brazil
- Dar es Salaam, Tanzania
- Bangkok, Thailand
- Kano, Nigeria
- Nairobi, Kenya
- Bamako, Mali
- Surabaya, Indonesia
Other tropical climates (group A)
Frequently asked questions
What does Aw mean in the Köppen climate classification?
Tropical (coldest month 18 °C or more). Not a rainforest or monsoon: the driest month gets under 100 minus yearly rainfall divided by 25 (in mm). The code is a short way of writing that: the first letter is the major group (A, tropical) and the letters after it say more about rain and temperature.
What is a tropical savannah climate like?
Hot all year, with a clear dry season. Warm throughout, with a wet season and a distinct dry season long and dry enough for grassland and scattered trees rather than closed forest.
How much of the world has a Aw climate?
13% of the world's land outside Antarctica was Aw in 1991 to 2020, about 17,895,072 km² (Beck et al. 2023, 1 km maps).
Will the Aw climate zone grow or shrink?
Under the middle-of-the-road scenario (SSP2-4.5), the area of Aw in 2071 to 2099 is 12.1% larger than in 1991 to 2020. This is a model projection, not a forecast, and it differs under other scenarios (see the table on this page).
Data: Beck et al. (2023), CC BY 4.0. See data sources and licences. Köppen-Geiger classes describe long-term averages, not weather.