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Major hot deserts in northern hemisphere are located between 20-30 degree north and on the western side of the continents. Why? Explain.

Topic:  Geographical features and their location-changes in critical geographical features (including water-bodies and ice-caps) and in flora and fauna and the effects of such changes.

2. Major hot deserts in northern hemisphere are located between 20-30 degree north and on the western side of the continents. Why? Explain.(250 words)

Reference: Physical Geography by Savindra Singh

Why this question:

The question is straight from the static portions of GS paper I, theme physical geography.

Key demand of the question:

One should explain the reasons owing to which all the Major hot deserts in northern hemisphere are located between 20-30 degree north and on the western side of the continents.

Directive:

Explain – Clarify the topic by giving a detailed account as to how and why it occurred, or what is the particular context. You must be defining key terms where ever appropriate, and substantiate with relevant associated facts.

Structure of the answer:

Introduction:

Briefly on a map show the locations of major hot deserts.

Body:

The hot deserts lie along the Horse Latitudes or the Sub-Tropical High Pressure Belts where the air is descending, a condition least favorable for precipitation of any kind to take place.
• The rain-bearing Trade Winds blow off-shore and the Westerlies that are on-shore blow outside the desert limits.
• Whatever winds reach the deserts blow from cooler to warmer regions, and their relative humidity is lowered, making condensation almost impossible.
• There is scarcely any cloud in the continuous blue sky. The relative humidity is extremely low, decreasing from 60 per cent in coastal districts to less than 30 per cent in the desert interiors. Under such conditions, every bit of moisture is evaporated and the deserts are thus regions of permanent drought. Precipitation is both scarce and most unreliable.
• On the western coasts, the presence of cold currents gives rise to mists and fogs by chilling the on-coming air. This air is later warmed by contact with the hot land, and little rain falls. The desiccating effect of the cold Peruvian Current along the Chilean coast is so pronounced that the mean annual rainfall for the Atacama Desert is not more than 1.3 cm.

Conclusion:

Conclude with a reassertion that the climate, geography have a major role to play in deciding the locations of these hot deserts.