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Semi-arid climate

earth science Maturity 9-11 Next article →

A semi-arid climate is a specific type of dry environment. These regions are also known as steppe or semi-desert climates. They exist in a middle ground between very wet areas and extremely dry deserts. In these places, the amount of rain that falls is less than the amount of water lost to evaporation. However, they still receive more moisture than a true desert. This balance of water shapes the entire landscape.

BS climate
BS climate

Scientists use the Köppen climate classification system to define these regions. This system identifies steppe climates, labeled as BSh or BSk, as intermediates. They sit between desert climates (BW) and humid climates (A, C, or D). To find the precipitation threshold, scientists follow a specific mathematical process. First, they multiply the average annual temperature in Celsius by 20. Next, they add a value based on seasonal rain. If 70% of rain falls in the summer, they add 280. If 30% to 70% falls in summer, they add 140. If less than 30% falls in summer, they add nothing.

Koppen-Geiger Map v2 BSh 1991–2020
Koppen-Geiger Map v2 BSh 1991–2020

A location is classified as a steppe climate if its annual precipitation is less than that calculated threshold. It must also be more than half of that threshold. Once a location is identified as a BS-type climate, scientists separate it into two categories. They use a mean annual temperature isotherm to make this distinction. If the mean temperature is above this line, it is a hot semi-arid climate (BSh). If the temperature is below it, it is a cold semi-arid climate (BSk).

Les Falaises de Bandiagara
Les Falaises de Bandiagara

Hot semi-arid climates (BSh) are often found near tropical or subtropical regions. These areas usually sit at latitudes between the high tens and mid-30s. They are often located near tropical savanna or humid subtropical climates. These regions frequently appear on the fringes of subtropical deserts. They experience hot or extremely hot summers and warm to cool winters. Common locations include Africa, Australia, the Indian subcontinent, and the edges of the Iranian plateau.

Koppen-Geiger Map v2 BSh 1991–2020
Koppen-Geiger Map v2 BSh 1991–2020

Many diverse places share the hot semi-arid climate. In Australia, much of the Outback near central deserts has this climate. In South Asia, India and Pakistan experience seasonal monsoons. These monsoons create short, well-defined wet seasons. Other examples include northern Mexico and the Southwestern United States. Parts of South America, such as the Gran Chaco, also feature this climate. In Europe, BSh climates are found in southeastern Spain and parts of Greece.

Mitchell grass downs post rain Boulia Shire Queensland P1070007
Mitchell grass downs post rain Boulia Shire Queensland P1070007

Cold semi-arid climates (BSk) are different in many ways. These are typically found in elevated temperate zones. They usually sit between the mid-30s and low 50s latitudes. These areas are often in continental interiors far from large bodies of water. They feature warm to hot dry summers. However, their summers are usually not as hot as BSh regions. Unlike hot climates, BSk areas have cold or even freezing winters.

Hell Creek State Park
Hell Creek State Park

Cold semi-arid regions often experience significant weather changes. They may see snowfall during the winter months. These areas tend to have higher elevations than hot semi-arid regions. They also experience large diurnal temperature variations. This means the temperature can swing by 20 °C (36 °F) or more between day and night. Such large swings are rare in hot semi-arid climates. These regions are common in central Asia, the western United States, and the Middle East.

Koppen-Geiger Map v2 BSk 1991–2020
Koppen-Geiger Map v2 BSk 1991–2020

The vegetation in these climates is limited by the lack of moisture. Because they cannot support large forests, these lands are dominated by grasses or shrubs. You will often see short, thorny, or scrubby plants growing there. This type of environment is vital for understanding different biomes. It shows how small changes in precipitation can change the entire look of the Earth. These semi-arid zones connect the lush, wet parts of our world to the barren, dry deserts.

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🖼️ Images & Media (6)
File:BS climate.png
BS climate.png
File:Les Falaises de Bandiagara.jpg
Les Falaises de Bandiagara.jpg
File:Koppen-Geiger_Map_v2_BSh_1991–2020.svg
Koppen-Geiger_Map_v2_BSh_1991–2020.svg
File:Mitchell grass downs post rain Boulia Shire Queensland P1070007.jpg
Mitchell grass downs post rain Boulia...
File:Koppen-Geiger_Map_v2_BSk_1991–2020.svg
Koppen-Geiger_Map_v2_BSk_1991–2020.svg
File:Hell Creek State Park.jpg
Hell Creek State Park.jpg
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