Write a geographical account of Hot Desert Climate under the following: (a) Location (b) Characteristic features, (c) Vegetation, (d) Human activities.

Hot Desert Climate

(a) Location

Hot deserts are mainly found between about 15° and 30° north and south of the Equator, especially on the western sides of continents and in continental interiors. They occur in the belt of subtropical high pressure where dry, descending air prevents cloud formation and rainfall.

Examples include the Sahara in North Africa, Arabian Desert, Thar Desert, Namib and Kalahari deserts in southern Africa, Atacama Desert in South America, deserts of south-western USA, and the Great Australian Desert.

(b) Characteristic features

The climatic graph below shows the very low rainfall and persistently high temperature of a hot desert climate.

• Temperatures are high throughout the year. Day temperatures may exceed 38°C and may rise to about 50°C in some deserts.
• There is a large diurnal range of temperature: days are intensely hot, while nights may be cold because clear skies permit rapid loss of heat by radiation.
• Rainfall is very low, unreliable and usually below 250 mm annually. In the graph, the annual total is only 25 mm.
• When rain falls, it is often convectional, sudden and violent, producing flash floods in dry valleys.
• Skies are generally clear, sunshine and solar radiation are intense, and evaporation is high.
• Relative humidity is low, often about 30% or less.
• Dry descending air of the subtropical high-pressure belt produces arid conditions. Cold currents, such as the Canary and Benguela currents, intensify aridity along some west coasts.
• Dust storms and sand storms are common. Soils are mainly sandy, stony or rocky and have little humus.

(c) Vegetation

• Vegetation is sparse, scattered and widely spaced because of inadequate moisture.
• The plants are mainly xerophytes, that is, plants adapted to drought. Common examples are cactus, acacia, thorny shrubs, grasses and herbs.
• Plants often have long tap roots or widespread shallow roots to obtain scarce water.
• Some have thick, fleshy or succulent stems for storing water.
• Leaves are small, waxy, leathery, hairy, needle-like, or reduced to spines or thorns, thereby reducing transpiration.
• Date palms occur around oases where underground water is available. Some plants are salt-tolerant halophytes.
• Annual grasses and herbs grow rapidly after short periods of rain, flower, produce seeds and die before the next dry period.

(d) Human activities

• Nomadic pastoralism: camels, goats and sheep are reared as herders move in search of water and pasture.
• Oasis and irrigated farming: dates, vegetables, wheat, millet, sorghum and other crops are grown where river water, wells or underground water is available.
• Mining and petroleum production: oil, natural gas, phosphates, salt and other minerals are extracted in many desert areas.
• Trading and transport: caravan routes and modern roads link settlements and move goods across deserts.
• Tourism and energy generation: desert scenery attracts tourists, while the abundant sunshine favours solar-energy projects.