The arid expanse covering north africa is called

The Sahara Desert

The arid expanse covering the northern part of Africa is called the 'Sahara Desert'.

Explanation:

The total area of the Sahara desert is 92,00,00 sq. kilometers. It stretches east-west across the entire northern part of Africa and consumes about 25% area of the continent. It houses 10 African countries and forms a natural physio graphic boundary between the world to the north and the rest of the African continent. Out of all the hot deserts in the world, the Sahara desert is the largest and the driest.