Climatic Conditions:

Rainfall: The aridity of deserts is the most outstanding feature of the desert climate. Few deserts whether hot or mid-latitude have an annual precipitation of more than 10 inches while in others less than 0.02 inches. The hot deserts lie astride 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 reaches the deserts blow from the cooIer to the warmer regions, and their relative humidity is lowered, making condensation almost impossible.

Temperature: The deserts are some of the hottest spots on earth and have high temperatures throughout the year. There is no cold season in the hot deserts and the average summer temperature is around 30°C. The highest shade temperature recorded is 58°C at Al Azizia, 25 miles south of Tripoli, Libya, in the Sahara. The diurnal range of temperature in the deserts is very great.

Natural Vegetation: All deserts have some form of vegetation such as grass, scrub, herbs, weeds, roots or bulbs. Though they may not appear green and fresh all the time, they lie dormant in the soil awaiting rain which comes at irregular intervals or once in many years. The environment, so lacking in moisture and so excessive in heat, is most unfavourable for plant growth and significant vegetation cannot be expected. The predominant vegetation of both hot and mid-latitude deserts is xerophytes or drought-resistant scrub. This includes the bulbous cacti, thorny bushes, long-rooted wiry grasses and scattered dwarf acacia. Trees are rare except where there is abundant ground water to support clusters of date palms.

Life in the Deserts: Despite its inhospitality, the desert has always been peopled by different groups of inhabitants. They struggle against an environment deficient in water, food and other means of livelihood. The desert inhabitants may be grouped under the following categories - The primitive hunters and collectors (The Bushmen and The Bindibu), the nomadic herdsmen (The Tuaregs of the Sahara, the Gobi Mongols and The Bedouin of Arabia), the caravan traders, the settled cultivators and the mining settlers.