Note4Students
From UPSC perspective, the following things are important :
Prelims level: Death Valley, Mojave Desert
Mains level: Not Much
California’s Death Valley registered a temperature of 54.4 degrees Celsius or 129.9 degrees Fahrenheit on August 16, 2020, which, once verified, could be the hottest temperature ever recorded on Earth.
Some years back, there was a question in the mains:
Major hot deserts in the northern hemisphere are located between 20-30 degree north and on the western side of the continents. Why?
Death Valley and its location
- Death Valley is a desert valley in Eastern California, in the northern Mojave Desert, bordering the Great Basin Desert.
- It is one of the hottest places on Earth, along with deserts in the Middle East and the Sahara.
- The valley is extremely dry because it lies in the rain shadow of four major mountain ranges (including the Sierra Nevada and the Panamint Range).
- Moisture moving inland from the Pacific Ocean must pass eastward over the mountains to reach Death Valley; as air masses are forced upward by each range, they cool and moisture condenses, to fall as rain or snow on the western slopes.
- When the air masses reach Death Valley, most of the moisture has already been lost and there is little left to fall as precipitation.
Key factors leading to its high temperature
- Solar heating: The valley’s surface (consisting of soil, rocks, sand, etc.) undergoes intense solar heating because the air is clear and dry, and the land is dark and sparsely vegetated. This is especially noticeable in summer when the sun is nearly directly overhead.
- Trapping of warm air: Warm air naturally rises and cools; in Death Valley, this air is subject to continual reheating as it is trapped by high, steep valley walls and recycled back to the valley floor.
- Migration of warm air from other areas (advection): Warm desert regions adjacent to Death Valley, especially to the south and east, often heat air before it arrives in Death Valley.
- Warm mountain winds: As winds are forced up and over mountains (e.g., the numerous ranges west of Death Valley), the winds can be warmed in several ways. The resulting dry, warm winds are known as foehn winds.
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