THE SIMPLIFIED KÖPPEN’S CLIMATE CLASSIFICATION SYSTEM

VIDEO LESSON

LESSSON OBJECTIVES

By the end of this lesson, you will be able to:

• Explain climatic classification method commonly used by Köppen.
• Discuss the five major terrestrial climatic types of the Köppen system.

BRAINSTORMING QUESTIONS

Why Köppen climatic classification method is commonly used?

Which climate types are found in Ethiopia, according to modified Köppen’s climatic classification schemes?

Keywords

• Ecotone
• Meso-thermal
• Micro-thermal

THE SIMPLIFIED KÖPPEN’S CLIMATE CLASSIFICATION SYSTEM

Dear Online Learner! Because of its simplicity and strong alignment with climatic areas, natural vegetation, and soil types, the Köppen climate classification system is commonly used for classifying world climate.
Köppen observed and mapped the ecotone (the zone where two biomes meet), then utilized temperature and precipitation data to construct equations that defined the climatic boundary between the two biomes. Köppen published his initial climate classification scheme in 1900 and revised it in 1940

Based on the aforementioned criteria, the Köppen system distinguishes between five major terrestrial climatic types:

1. Tropical climate (A): All months have an average temperature above 18^o C (64^oF). There is no real winter season because every month of the year remains warm.
2. Dry Climate (B): It has deficient precipitation most of the year
3. Meso-thermal or Mid-latitude Mild (C): Average temperature of the coldest month is below 18⁰C (64⁰ F) and above -3⁰C (27⁰F).
4. Micro-thermal or Mid-latitude Cold (D): The average temperature of the warmest month exceeds 10⁰C (50⁰F), and the coldest monthly average drops below -3⁰C (27⁰F).
5. Polar Climate (E): It has extremely cold winters and summers. The average temperature of the warmest month is below 10⁰ C (50⁰F). Given that all months are cold, there is no real summer season. A new group, highlands (H), was later created to account for the significant climate changes in mountainous areas over short distances.

Figure 2.1:A simplified overview of the major climate types, according to Köppen

MODIFIED KÖPPEN’S CLIMATIC CLASSIFICATION SCHEMES

Figure-2.2. Improved Köppen-Geiger classifications of our world:
Part (a) shows the present-day map (1980–2016) and (b) the future map (2071–2100).
Source – Present and future Köppen-Geiger climate classification maps at 1-km resolution @www.gloh20rg/ Köppen

Dear Online Learner! Using air temperature (⁰C) and precipitation (mm y^-1) criteria from high-resolution climatic datasets, the present Köppen-Geiger map was developed. The current Köppen-Geiger classification didn’t consider the rising levels of greenhouse gases in the atmosphere.

Source: Beck et al.: Present and future Köppen-Geiger
climate classification maps (2018)
“Figure 2.3. Köppen-Geiger climate classification map for Ethiopia (1980-2016)”

Rudolf Geiger, a climatologist, altered the Köppen classification system in 1961 to improve the alignment of climate zones and biomes. By merging appropriate first, second, and third-order subdivisions, modified Köppen–Geiger climatic types are produced.

The tropical wet climate (A)

From the equator to 15^o to 25^o north and south latitudes, the tropical wet climate (A) exists.

The average temperature in all monthly records exceeds 18^o C (64.4^oF) and more than 60 inches (>1500mm) of rain falls each year

The climate in this category is divided into three minor Köppen climatic types.

1. Tropical wet or equatorial rainforest climate (Af):

• Af refers to a tropical environment with year-round precipitation.
• Monthly T^o differences are fewer than 3^oC.
•  Cumulus and cumulonimbus clouds occur practically every day early in the afternoon.
• The average daily high T^o 32^oC, while the average nighttime temperature is 22^oC.
•  Found in areas such as Amazon rain forest and Congo basin.

2. Tropical monsoon climate (Am)

• Am denotes a climate with yearly rainfall similar to or greater than Af.
• But the majority of precipitation falling during the 7 to 9 hottest months.
• There is extremely little rain throughout the dry season.
• Found in regions such as parts of India and South East Asia.

Tropical wet and dry or savanna (Aw)

•  Characterized by a prolonged dry season in the winter.
• During the rainy or summer season, precipitation is frequently less than 40 inches.
• Examples: the African savanna and the tropical regions of South America.
•  The difference between Aw and Am climates is determined by annual precipitation and the driest month’s precipitation, using the formula below: a=3.94-r/25.

Dry climate (B)

Dry climates are generated by their location:

• In trade wind belts,
• On the leeward side of high mountains, and
• In the interior of continents along cool ocean currents.
• During most months, mean evapotranspiration tends to exceed mean precipitation.
• Characterized by a lack of precipitation for the majority of the year, which limits vegetation.
•  Based on yearly temperature and the wettest month of the year, the dry climate is classified into two minor classes.

1. Desert (BW): A true arid climate dominated by xerophytes vegetation that covers 12% of the earth’s land surface. It is found between 15 and 300 North and South. Vast deserts such as the Sahara or Gobi are included.
2. Dry Semiarid or Steppe (BS): A grassland climate that encompasses 14% of the planet’s land area. The boundary between BW and BS is established using the formula: r=0.44t-8.5/2.

Dry (B) climates are further classified based on annual temperature.

1. The letter “h” when the mean annual temperature is greater than 18⁰C (64.4⁰F) and
2. The letter “k when the mean annual temperature is less than 18⁰C (64.4⁰F).

Desert climates are further divided into:

1. Hot/tropical/desert (BWh) climates, which have an average annual temperature greater than 18⁰C (64.4⁰F), and
2. Middle latitude cold desert climates (BWk), which have an average annual temperature less than 18⁰C.
3. Hot dry semiarid or tropical steppe (BSh) climate, with a mean annual temperature above 18⁰C, and
4.  Cold dry semiarid or middle-latitude latitude cold steppe climate (BSk), with mean annual temperature below 18⁰C, are two third-order divisions of steppe climates.

Mid-latitude Mild or Meso-thermal (C)

• Warm and humid summers alternate with mild winters in this region, which is located between 25 and 40⁰ latitudes.
•  Frequently dominated by convective thunderstorms during the summer months.
• The seasonal distribution of precipitation further divides mid-latitude climate into three distinct climatic subgroups.

• I. Cf climate:
• Characterized by precipitation throughout the year, with more than 1.2 inches of precipitation in the driest month of the summer season.
• Most common climate in Western Europe.
• There are two third-order sub-divisions within this climatic type:

1. Humid subtropical (Cfa), Is found along east costs of continents are characterized by warm humid summers with frequent thunderstorms; and precipitation coming from mid-latitude cyclones during the mild winter season); and
2. Marine west coast (Cfb), is found in the western sides of continents are characterized by humidity, short dry summer, and persistent mid-latitude cyclones (causing heavy precipitation during mild winters).

• II. Cw Climate:
• Characterized by dry winters, and has 10 times more precipitation in the wettest month of summer season than the driest month of winter season.
• Dominant climatic type in China
• III. Cs (Mediterranean):
• The primary rainfalls from mid-latitude cyclones during the winter season. Extreme summer aridity is caused by the sinking airs of the subtropical highs. The wettest winter month receives at least three times the amount of rain as the driest summer month.

Mid-latitude Cold or Micro-thermal (D) Climate

• Also called continental climate
• Found on the poleward side of the moderate (C) mid-latitude climate.
• Warm to cool summers
• Snowstorms, high winds, and brutal cold from polar or arctic air masses characterize the harsh winters.

• Df climate (humid cold climate with no dry season),
• Dw climate (humid cold climate with dry winters), and
• DS climate (humid cold climate with wet winters) is the three sub-classes of this climate type.

Polar Climate (E)

• Characterized by cold temperatures year-round
• Found on the landmasses of Greenland and Antarctica, northern coastal portions of North America, Europe, and Asia.

• The two minor types of polar climate are
•  Polar tundra (ET) is defined by permafrost
• The warmest month’s average temperature is greater than 0⁰C (32⁰F) but less than 10⁰C. (50⁰F).
• Mosses, lichens, dwarf trees, and scattered woody shrubs can be found scattered throughout the polar tundra.
• A polar ice cap (EF) is permanently covered with snow and ice.
• The average temperature of the warmest month is 0⁰C (32⁰F) or below.

Highland Climate

• The afro-alpine zones on the highest parts of the Ethiopian plateaus
• The Senate Plateau (Bale Zone),
• Simien Mountains (north Gonder), Mount Guna (south Gonder),
• Amara Saint (South Wollo),
• Choke Mountains (Gojam) are examples

The Merits and Demerits of Köppen’s System

Dear Online Learner! The Köppen system has been criticized by several people, including for reasons.

• Extreme events, such as a periodic drought or a common cold for, are as reasons important in controlling vegetation distribution as the mean conditions on which Köppen’s scheme is based;

• In addition to precipitation and temperature, sunlight and wind are important to vegetation;
• Natural vegetation can only respond slowly to environmental change (as a result, the vegetation zones visible today are in part adjusted to past climates);
• It is inconsistent since it based A, C, D, and E zones on mean temperature, whereas zone B is based on a precipitation-evaporation ratio;
• It is insufficiently thorough since it ignores the climate of mountainous regions and fog-affected regions, and
• The boundaries of Köppen’s climatic classifications are too empirical.

The strength of Köppen’s system:

• Its ability to provide a clear, quantifiable, and straightforward method based on temperature and precipitation.
• Acknowledges the link between vegetation kinds and climate.