The aridity of the hot deserts is mainly due to the effects of off-shore Trade Winds, hence they are also called Trade Wind Deserts.
The major hot deserts of the world are located on the western coasts of continents between latitudes 15° and 30°N. and S (Question asked in Previous Mains Exam).
They include the biggest Sahara Desert (3.5 million square miles). The next biggest desert is the Great Australian Desert. The other hot deserts are the Arabian Desert, Iranian Desert, Thar Desert, Kalahari and Namib Deserts.
The hot deserts lie along the Horse Latitudes or the Sub-Tropical High Pressure Belts where the air is descending, a condition least favourable 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 dessicating 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.
The major hot deserts of the world are located on the western coasts of continents between latitudes 15° and 30°N. and S (Question asked in Previous Mains Exam).
They include the biggest Sahara Desert (3.5 million square miles). The next biggest desert is the Great Australian Desert. The other hot deserts are the Arabian Desert, Iranian Desert, Thar Desert, Kalahari and Namib Deserts.
The hot deserts lie along the Horse Latitudes or the Sub-Tropical High Pressure Belts where the air is descending, a condition least favourable 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 dessicating 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.
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