Climate

• The hot desert biome is characterised by high temperatures and low levels of precipitation.
• There is usually less than 100mm of rain per year.
• Rainfall is lowest at the Atacama Desert of Chile where averages are less than 15 mm per year.
• In the Atacama Desert when it does rain it tends to be concentrated in short bursts
• There is rapid runoff which leaves to low levels of infiltration ( the process whereby rain enters the soil )
• There are also high rates of evaporation.
• Evaporation rates regularly exceed rainfall rates.
• Sometimes rain starts falling and evaporates before it reaches the ground.
• In the North American Hot Deserts ( The Chihuahua Desert, the Sonora Desert, the Mojave Desert ) precipitation is mainly seasonal i.e. they receive either winter or summer precipitation.
• The Sonoran Desert is one of the wettest deserts in North America and receives between 75 and 250 mm of rain per year
• The summer rain in the Sonoran Desert are short and heavy, while the winter rains are longer and lighter.
• Desert temperatures are characterised by their extremes.
• Temperatures are usually more than 30 degrees in the summer as the sun shines from almost vertically overhead.
• Cloudless skies allow daytime temperatures to rise rapidly.
• Very little heat is lost by reflection and it is quickly absorbed by the bare rock or stony surface.
• But with no cloud to blanket it, about 90% of the solar energy hitting the ground during the day is radiated back to space after nightfall.
• This leads to large diurnal (daily) ranges.
• The average daily temperature in the Chihuahuan desert is 38 degrees while the average nightime temperature is -4 degrees.
• As a result ‘night is the winter of the desert’ is often used to describe the Hot Desert Climate.
• deserts have a low latitude, meaning they are found close to the equator ( about 15-30 degrees north and south of the equator)
• the low latitude is a high pressure belt meaning that air is constantly sinking to the ground and warming up
• The high pressure belt causes constant evaporation and prevents cloud and rain from forming.
• Deserts lie in the path of the dry trade winds that blow towards the equator and are therefore warming up and absorbing moisture as they blow across deserts.
• hot deserts lie beside cold ocean currents. These cold ocean currents prevent winds and rain from reaching land. All the rainfall falls over the sea leading to drier conditions inland.
• The Canaries Current travels along the western coast of Africa preventing rain from reaching the Sahara Desert.