Dry and Warm Temperate Climates (Groups B and C)
Geography › El Niño and Climate Classification · Topic 9.6
Dry climates, Group B, are those where evaporation exceeds precipitation, divided into hot and cold deserts and the steppe. Warm temperate climates, Group C, have mild winters, with the coldest month between minus 3 and 18 degrees Celsius, and include the Mediterranean, the humid subtropical, the marine west coast and the dry-winter types.
6 min read · UPSC Prelims · Geography · El Niño and Climate Classification
At a Glance
- Group B Evaporation exceeds precipitation
- BW Desert, under 25 cm of rain
- BS Steppe, semi-arid
- Cs Mediterranean; wet winter, dry summer
- Cfa and Cfb Humid subtropical and marine west coast
- Exam link UPSC Prelims, Geography: El Niño and Climate Classification
Where Does It Fit?
This is the sixth topic of the category on El Niño and climate classification. The previous topic described the tropical humid climates, and this one moves to the dry belts and the mild mid-latitude climates. The last topic covers the cold snow-forest and polar climates. Previous topic: Tropical Humid Climates (Group A). Next topic: Cold Snow-Forest and Polar Climates (Groups D and E).
What Are the Dry Climates of Group B?
In short: dry climates are not defined by a low temperature, but by evaporation exceeding rainfall.
Group B covers about a quarter to a third of the land surface, and is divided into the desert, with the letter W, and the steppe, with the letter S; the second letters h and k stand for hot and cold. There are four main types.
| Type | Features | Examples |
|---|---|---|
| BWh: hot desert | Rainfall under about 25 cm; very hot days and cool nights; annual mean above 18 degrees; sparse xerophytic vegetation such as cactus, date palm, thorny shrubs | Sahara, Arabian desert, Thar, Kalahari, Australian desert, Sonoran |
| BWk: cold desert | Dry, with cold winters; located in the interior of continents or in the rain shadow of mountains | Gobi, Taklamakan, Patagonia, Great Basin of the United States |
| BSh: hot steppe | Semi-arid, with 25 to 75 cm rainfall, in a transition from desert to savanna; thorn scrub | Sahel, rain-shadow areas of the Deccan plateau |
| BSk: cold steppe | Semi-arid and cool, with short grass on rich soils | Prairies of North America, Pampas, Eurasian steppe, Veldt |
Aridity has four causes. The first is the subtropical high pressure belt at about 15 to 30 degrees, where air sinks and warms, which explains the Sahara, Arabia and the Thar, as in Pressure Belts and Pressure Cells. The second is the rain shadow of mountains, which explains Patagonia and the Great Basin, as in Precipitation and Types of Rainfall. The third is a cold ocean current along a western coast, which cools the air and prevents rain, as in the Atacama and the Namib, as in Effects of Ocean Currents. The fourth is distance from the sea, which explains the Gobi and Turkestan. Deserts have a huge daily range of temperature, and the occasional rain causes flash floods. Oases, exotic rivers like the Nile and mineral wealth such as oil in Arabia support settlements, while nomadic herding is the main way of life.
What Are the Warm Temperate Climates of Group C?
| Type | Location | Climate and economy |
|---|---|---|
| Cs: Mediterranean | Western sides of continents at 30 to 45 degrees: Mediterranean basin, California, central Chile, Cape Town region, southwest and south Australia | Hot, dry, sunny summers under the subtropical high; mild, rainy winters when the westerlies and temperate cyclones move equatorward; evergreen shrubs such as maquis and chaparral; citrus fruits, grapes, olives, figs; wine; tourism |
| Cfa: humid subtropical | Eastern sides of continents at 25 to 40 degrees: southeastern United States, southeastern China, Uruguay, northern Argentina, eastern Australia, southern Japan | Hot, humid summers with thunderstorms and sometimes typhoons or hurricanes; mild winters; rain in all months; dense population; rice, cotton, tea, tobacco, maize |
| Cfb: marine west coast | Western sides of continents at 40 to 60 degrees: northwestern Europe, southern Chile, British Columbia, New Zealand, southeastern Australia | Cool summers, mild winters, rain all year from the westerlies and temperate cyclones; deciduous forests; dairy farming, wheat, fruits, a strong industrial base |
| Cw: dry winter | Northern India, southern China, parts of southern Africa at higher elevation | Hot, rainy summer monsoon and dry winter; Köppen Cwg describes the Ganga plain; rice, wheat, sugarcane, cotton |
The climate of the Mediterranean is a special case, since it is the only climate in which rain falls in winter and the summer is dry, because the zone of winds shifts with the Sun, as in General Circulation of the Atmosphere. This is why the Mediterranean regions are called the orchards of the world. The humid subtropical climate is sometimes called the China type, and the marine climate the British type.
Why Do These Climates Matter Today?
- Desertification: the dry edges of the steppe and savanna are degrading because of overgrazing, deforestation and drought, as the Sahel shows; the African Great Green Wall initiative aims to restore a belt of land across the Sahel. India’s land degradation is discussed under the United Nations Convention to Combat Desertification, which India hosted in 2019.
- Wildfires: Mediterranean climate regions, such as California, Greece, Portugal and Australia, are seeing more intense fires as hot, dry summers lengthen with warming.
- Water stress: a warming climate is expected to expand the dry zones, making water management important in the Mediterranean regions in particular.
As an analytical point, the world’s best wine, fruit and wheat lands lie in the Group C and BS zones, so a shift of boundaries has direct effects on food and trade.
Why Is This Topic Important?
- Core groups Deserts and Mediterranean asked often
- Causes Four reasons for aridity
- Present issues Desertification and fires
What Came Next?
The last topic of the category describes the cold snow-forest and polar climates. Next topic: Cold Snow-Forest and Polar Climates (Groups D and E).
Key People and Terms
- Xerophyte Plant adapted to dry conditions
- Steppe Semi-arid grassland
- Maquis Mediterranean scrub
- Chaparral Californian scrub
- Humid subtropical Cfa climate of eastern margins
- Desertification Land degradation in dry areas
Exam Corner
Points to Remember
- Deserts get under 25 cm of rain.
- Mediterranean: wet winter, dry summer.
- Cfa is on the eastern side of continents.
- Cfb is on the western side.
- The Atacama is a cold current desert.
Do Not Confuse With
- Desert and steppe Under versus over 25 cm
- Cfa and Cfb East versus west coast
- Mediterranean and marine climates Dry summer versus rain all year
Memory Hook
Highs, shadows, cold currents and distance make deserts; west coast wets in winter, east coast in summer.
Mains Angle
Questions ask for causes and features. These points add depth.
- Causes High pressure, relief, currents
- Production Mediterranean fruits and wines
- Threat Desertification
A Question You May Face
An original practice question, not a past paper question.
“Explain the causes of the world’s hot deserts and compare the Mediterranean and the marine west coast climates.”
How to Answer
- Deserts Four causes.
- Mediterranean Winter rain.
- Marine Rain all year.
- Today Desertification and fires.
GS Relevance
Frequently Asked Questions
What are the dry climates in the Köppen scheme?
Group B dry climates are those where evaporation exceeds precipitation. They are divided into hot deserts, cold deserts, hot steppes and cold steppes, with rainfall under about 25 centimetres in the deserts and 25 to 75 centimetres in the steppes.
Why are hot deserts located on the western sides of continents?
Hot deserts lie in the subtropical high pressure belt where air sinks, and on the western sides of continents, cold ocean currents and offshore trade winds reduce moisture even more. This combination explains the Sahara, the Atacama, the Namib and the deserts of Australia.
What is the Mediterranean climate?
The Mediterranean climate, Cs, has hot, dry and sunny summers and mild, rainy winters. It occurs on the western sides of continents between 30 and 45 degrees, in the Mediterranean basin, California, central Chile, the Cape region of South Africa and southern Australia, and suits citrus fruits, grapes and olives.
What is the humid subtropical climate?
The humid subtropical climate, Cfa, is found on the eastern sides of continents between about 25 and 40 degrees. It has hot, humid summers, mild winters and rain in every month, and supports dense populations that grow rice, cotton, tea and tobacco, as in southeastern China and the southeastern United States.
What is the marine west coast climate?
The marine west coast climate, Cfb, lies on the western sides of continents between about 40 and 60 degrees, as in northwestern Europe and New Zealand. The westerlies and temperate cyclones bring rain throughout the year, with cool summers and mild winters, supporting dairy farming and deciduous forests.
PYQ Practice — Statement Analysis
1 The Mediterranean climate has rainfall mainly in summer.
It has winter rain and dry summers.
2 The Atacama Desert is partly due to a cold ocean current.
The Humboldt Current cools the coast.
3 The humid subtropical climate is on the eastern side of continents.
Examples are southeastern China and the southeastern United States.
4 The steppe receives less rain than a hot desert.
It receives more, about 25 to 75 cm.
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