Question

Albuquerque, New Mexico, receives an average of 20.7 centimeters \((8.07\) inches) of rainfall annually. Albuquerque is considered a desert under the commonly used Köppen climate classification. The Russian city of Verkhoyansk is located near the Arctic Circle in Siberia. Yearly precipitation at Verkhoyansk averages 15.5 centimeters \((6.05\) inches) about 5 centimeters ( 2 inches) less than Albuquerque, yet it is classified as a humid climate. Explain why this is the case.

Short answer

Verkhoyansk retains more moisture due to its cold climate, classifying it as humid, unlike Albuquerque's high evaporation desert climate.

Step-by-step solution

Understand Köppen Climate Classification

The Köppen climate classification system uses factors like temperature and precipitation to divide the world's climates into groups. A 'desert' climate (designated as 'B') under the Köppen system means very low precipitation, especially in relation to evaporation, which affects plant and animal life.

Examine Precipitation Levels

Albuquerque receives an average of 20.7 cm (8.07 inches) of rain annually, while Verkhoyansk receives 15.5 cm (6.05 inches) of rain annually. At first glance, Verkhoyansk might seem drier, but precipitation alone does not determine Köppen climate classification.

Consider Temperature and Evaporation Rate

Desert climates are characterized not only by low precipitation but also high evaporation rates. Albuquerque's hot desert climate means it has high evaporation rates, which makes the region arider, while Verkhoyansk has a much colder climate with low evaporation, retaining more moisture.

Role of Temperature in Humid vs. Desert Climate

Despite receiving less precipitation, Verkhoyansk is much colder and thus retains the moisture it receives. The ground remains moist for longer, supporting a different ecosystem than a desert. Thus, it aligns more with a humid (D) climate type in the Köppen classification.

Conclusion

Even though Verkhoyansk receives less precipitation than Albuquerque, its cold temperatures result in less evaporation and higher moisture retention. This makes its climate more humid according to the Köppen classification, despite its low precipitation rate.

Key concepts

Desert Climate

Desert climates, known as 'B' under the Köppen climate classification, are defined by their limited rainfall in contrast to high evaporation rates. A critical aspect of desert climates is the scarcity of water due to rapid evaporation processes, making it challenging for vegetation to thrive.
This category typically features arid landscapes with barren land and little plant life. In desert regions, the temperatures are often high, leading to increased evaporation, which removes moisture quickly from the ground. This high evaporation rate means that even limited rainfall evaporates before it can nourish the soil.
Hence, a place like Albuquerque, with moderate rainfall, can still be classified as a desert due to its high temperatures that lead to significant water loss.

Humid Climate

Humid climates, such as those under the 'D' classification in the Köppen system, are much cooler and retain moisture better than desert climates. The classification 'D' implies climates that have a higher capacity for moisture retention, even when precipitation is not very high.
In areas like Verkhoyansk, the low temperatures mean that there is minimal evaporation, allowing even a small amount of precipitation to remain in the soil for longer. This leads to a wet environment year-round, with conditions that can support ample vegetation despite low rainfall amounts.
To contextualize, while Verkhoyansk annually receives less precipitation than some desert areas, the persistent cold keeps the atmosphere moist enough to support a "humid" classification.

Evaporation Rate

Evaporation is a key player in determining the climate classification of a region. This process involves water transforming from a liquid to a gas, dissipating into the atmosphere.
In warm regions, like deserts, high temperatures fuel an increased evaporation rate that contributes significantly to an arid landscape. Because water evaporates quickly in such climates, the soil remains dry and unable to support much plant life.
On the other hand, in colder climates, evaporation rates are lower. This means that whatever precipitation the area receives tends to stay longer on the surface or within the soil. Therefore, colder areas can maintain a humid climate because they can store more water, supporting a lush environment even if the precipitation is limited.

Temperature Influence on Climate

Temperature has a pivotal influence on determining the climate of a region. It affects both the rate of evaporation and the overall ability of an area to retain moisture.
In warmer climates, high temperatures accelerate evaporation, leading to drier conditions even if there is considerable rainfall. This is why places like Albuquerque are classified as having desert conditions.
Conversely, in colder regions, such as Verkhoyansk, the low temperatures lead to slower evaporation rates. As a result, the limited precipitation these areas receive remains within the environment, increasing moisture availability. This retention of moisture supports verdant ecosystems, defining these locales as humid despite their relatively low precipitation.
Thus, temperature is a determining factor as it regulates how much water stays in the environment versus how much is lost to the atmosphere.