Koeppen's classification of world climates

Köppen’s classification is primarily based on observed temperature and precipitation patterns, along with their seasonal distribution. These climatic elements help identify broad groups such as tropical, dry, temperate, continental and polar climates. Relief, population and soil may influence local conditions, but they are not the principal basis of this global climate classification.

The capital letter A is used for the tropical climate group in Köppen’s system. This group is characterised by high temperatures: the average temperature of every month is generally 18°C or above. B represents dry climates, C warm temperate climates, and E polar climates, so those letters cannot be correct for tropical humid conditions.

In Köppen’s classification, the capital letter B denotes the dry-climate group. It includes desert climates, coded BW, and steppe or semi-arid climates, coded BS. A represents tropical climates, C warm temperate climates and D cold snow-forest or continental climates. Therefore, B is the only suitable answer for dry climates.

The capital letter E represents the polar climate group in Köppen’s classification. In this group, the mean temperature of the warmest month remains below 10°C. The E group includes tundra (ET) and ice-cap (EF) climates. A, B and C refer respectively to tropical, dry and warm temperate groups, so option C is correct.

The capital letter C denotes the warm temperate climate group in Köppen’s system. These climates generally have a mild winter and a warm summer, with the coldest-month temperature remaining above the polar threshold. D represents colder continental or snow-forest climates, B represents dry climates, and E represents polar climates. Hence the option containing C is correct.

The capital letter D denotes the cold snow-forest, or continental, climate group in Köppen’s classification. These regions generally experience marked seasonal contrast, including cold winters, and are distinct from the milder C climates. A represents tropical climates, B dry climates and E polar climates. Therefore, the option labelled D correctly answers the question.

In Köppen symbols, the lowercase letter f means there is no distinct dry season; precipitation occurs in all seasons. It does not require exactly equal rainfall every month, but no season meets the system’s dry-season criterion. The letter s indicates dry summer and w indicates dry winter. Thus, option A expresses the correct general meaning.

The lowercase letter s indicates a dry summer. It is used in codes such as Csa and Csb for Mediterranean-type climates, where most precipitation falls during the cooler part of the year. The letter w indicates a dry winter, while f means no distinct dry season. Therefore, s should be understood as summer dry, not as a separate desert group.

The lowercase letter w means that winter is the dry season. In such climates, precipitation is concentrated mainly in the warmer months, while winter receives relatively little rain. This symbol should not be confused with s, which means dry summer, or f, which means no distinct dry season. Therefore, option C gives the correct interpretation of w.

In the code Af, A identifies the tropical group and f means there is no distinct dry season. Thus Af is tropical rainforest climate, characterised by high temperatures and rainfall in every month. Am is tropical monsoon climate, while Aw or As represents tropical savanna with a dry season. BW belongs to the dry group, so it cannot be Af.

Am is the code for tropical monsoon climate. The capital A places it in the tropical group, and m identifies the monsoon subtype, which has a short or less pronounced dry period compared with savanna climate. Desert climate belongs to the B group, tundra to ET, and ice-cap climate to EF. Hence tropical monsoon is the only correct option.

In Aw, A denotes tropical climate and w denotes a dry winter. Therefore, Aw is tropical savanna climate with a pronounced dry winter and most rainfall during the warmer season. A dry summer is represented by s, as in Mediterranean Csa, not by w. Snow-covered and polar climates belong to the E group, so those options are unrelated.

BW is the general Köppen code for desert climates. B identifies the dry-climate group and W identifies the desert subtype. A more detailed code may be BWh for a hot desert or BWk for a cold desert. ET is tundra, Cfa is humid subtropical, and Af is tropical rainforest, so none of those represents desert climate.

BS is the general code for steppe or semi-arid climate. The capital B places it in the dry-climate group, while S identifies the steppe subtype, which is drier than most humid climates but generally receives more precipitation than a desert. BW is desert, Af is tropical rainforest, and ET is tundra.

BWh can be decoded letter by letter: B means dry climate, W means desert, and h indicates the hot temperature subtype. Thus BWh represents hot desert climate, such as the climate found in many subtropical deserts. BWk denotes cold desert, EF ice cap and Af tropical rainforest, so those alternatives do not fit the code.

BWk denotes a cold desert climate. B identifies the dry group, W identifies desert, and the final k indicates the relatively cooler temperature subtype. By comparison, BWh denotes hot desert. Tropical rainforest is Af and marine west coast is generally Cfb, so neither can be represented by BWk. Therefore, the cold-desert option is correct.

Csa is a common Köppen code for Mediterranean climate with hot summers. C denotes warm temperate climate, s indicates a dry summer, and a indicates a hot summer. Other Mediterranean variants include Csb when summers are warm rather than hot. Cfa has no distinct dry season, Af is rainforest, and ET is tundra, so Csa is the best answer.

Cfb is the usual Köppen code for marine west coast, or oceanic, climate. C denotes a warm temperate group, f means there is no distinct dry season, and b indicates a warm but not excessively hot summer. BWh is hot desert, EF ice cap and Aw tropical savanna, so none of those describes marine west coast conditions.

Cfa is the common Köppen code for humid subtropical climate. C places it in the warm temperate group, f indicates no distinct dry season, and a indicates a hot summer. Dfd is a very cold continental climate, BWk is cold desert, and ET is tundra. Thus Cfa, rather than the other climate codes, matches humid subtropical conditions.

ET represents tundra climate. E denotes the polar climate group, and T identifies the tundra subtype. In tundra regions, the warmest month has a mean temperature above 0°C but below 10°C, so trees generally cannot form a continuous forest. BWh is hot desert, Am monsoon and Aw savanna, making option A correct.

In Köppen’s system, E denotes polar climates. The second letter F means that the mean temperature remains below 0°C in every month; therefore, permanent ice or ice-cap climate is coded EF. Tundra is ET because its warmest month is above 0°C but below 10°C. Af and BS belong to tropical rainy and semi-arid groups, respectively.

Group A represents tropical climates. Its defining thermal condition is that the mean temperature of every month is generally at least 18°C, so these climates occur mainly in low latitudes near the Equator. Polar climates are placed in Group E, while dry climates are placed in Group B. Mountain altitude can modify climate but does not define Group A.

The tropical rainforest climate is coded Af. Here A indicates a tropical climate and f indicates that there is no distinct dry season. Rainfall is therefore abundant and distributed through all or nearly all months, supporting dense evergreen rainforest. Snow-only, nearly rainless, and very short rainy-season conditions describe other climates, not Af.

Group B is the dry-climate group. Its defining idea is that available precipitation is insufficient to meet the moisture demand created by evaporation and temperature, producing a water deficit. BW represents desert conditions and BS represents steppe or semi-arid conditions. High humidity, permanent snow, and year-round cold belong to other climate characteristics.

BS is the Köppen code for steppe, or semi-arid, climate. It belongs to Group B and has more precipitation than BW desert climate, although moisture is still insufficient for humid conditions. Af is tropical rainforest, ET is tundra, and EF is ice cap. Thus, BS is the only option describing a semi-arid climate.