Mirages, Miracles & the Science of Deserts

My love for deserts is well established with my aiming to set the record to be the first Asian and first Indian who has visited all Deserts of the Earth. But it’s more than just this record for me; in fact it’s much more than that. I think deserts are profoundly spiritual places. Their silence can be deafening and the connection with your own self is sometimes a bit too close for comfort. The technologies of the world seem far away and so do the sounds of everyday life that we are so used to in our cities and towns. Initially it is eerie and unnerving but just try to stay there for a day longer and then another day to see the magic that takes over your mind. You are calmer yet scared, but one thing is for sure – You are more real. The pretentions that this world demands slowly strip away and you become closer to who you are – sometimes too close.

Deserts are indeed spiritual places where we realize our true size in comparison to the vastness of nature, on a land full of surreal structures carved by wind and water over millions of years. Yet paradoxically this emptiness seems to magnify everything as well and suddenly even the smallest insect is noticed or even the slightest sound is heard. Deserts are disorienting places for those of us who dwell in cities and it’s no over exaggeration when travellers speak of mirages and miracles. You see, these stories of the desert are as old as man, the man that first walked out of Africa a million years ago and recorded his existence in cave paintings and rock art that have stood the test of all elements till now because of the dryness of this timeless landscape. I have seen such rock art with my own eyes in the Sahara, the Syrian and the Kalahari Deserts.

We have to also realize that deserts are not really empty and devoid of life as we assume them to be or as they are portrayed in popular culture. Besides some small animals and a few hardy plants like cacti, many humans also call deserts their home and have adapted themselves to live in these godforsaken places. In fact through their hardships they have built a few qualities that we can all learn from – the qualities of generosity, hospitality, courage and calmness. It is indeed sad that these remote and inaccessible lands are also the refuge of those who deal in nefarious activities, thereby making deserts inherently dangerous places to be in. It is these locals who face the harshest brunt of the situation, and not us travellers passing through on the kindness of these beautiful strangers.

Playing tricks in world’s largest salt flat, Bolivia.The Science of Deserts

In simple terms and as explained in last Sunday’s editorial (3rd Mar’ 24), deserts are arid places where the average annual rainfall is less than 10 centimetres or 2.5 inches. They are not necessarily hot or sandy but can be cold or polar deserts too and instead of having topography of sand dunes, can have rocky or icy surfaces as well. These deserts are the largest biome on Earth, being around 1/3rd of the land surface and marginally bigger than all the forest cover.

When we speak of the various types of deserts, there are essentially 5 scientific classifications – Tropical, Relief, Continental Inland, Coastal and Polar Deserts. The hot deserts are found typically around the tropics on both hemispheres between 15 and 30 degrees latitude and are simply called ‘Tropical Deserts’. The science is that the lighter warm air from the tropics rises at the Equator due to Earth’s convection currents (the concept of Hadley cell & trade winds can be searched) and becomes heavy as it collects moisture on its way up, which results in rainfall. Due to this heavy constant rain we have dense rainforests near the equator, from the Amazon in South America to Congo in Central Africa and in the rainforests of Borneo and Papua New Guinea in Asia. However after pouring down on the land below the equator, the air left behind is dry and through the same convection currents the dry air flows towards the tropics on either side, further losing its moisture and water vapour on the way. So because of this drying air we first move from the dense forests to grasslands, then semi desert shrub-lands till we finally reach the ‘Tropical Deserts’ with minimal precipitation. Classic examples are the Sahara, Syrian, Arabian and Thar Deserts in the Northern Hemisphere and the Kalahari, the Great Australian Deserts in the South. Such ‘Tropical Deserts’ occupy the greatest land area on Earth amongst deserts, barring the polar deserts of Antarctica and The Arctic. It must be pointed out that the conditions in these ecosystems are clearly not tropical since we generally associate tropical areas with rain and heat. These are places of dry heat instead.

The other type of desert is the ‘Relief Desert’ which is found in the rain shadows or the leeward side of mountains. The precipitation takes place in the opposite windward side of the mountains and on the leeward side, the sinking and warming air masses break up the clouds and reduce precipitation. On such leeward side are many deserts of USA and Mexico such as the Great Basin and Mojave against the ranges of Sierra Nevada and Cascade Mountains, and the Chihuahua desert which is on the leeward side of Sierra Madre Occidental. The semi-arid Patagonia of Argentina is also a relief desert against the mighty Andes range, whereas The Great Kavir and Lut of Iran in West Asia are similar examples, next to the Zagros Mountains.

Then there are the ‘Continental Inland Deserts’ which lie in the center of great land masses which don’t receive moist air even without any barriers of mountains (as in the case of Relief Deserts). By the time the air mass has come all the way inland from the sea, it has lost all its moisture and the land below becomes arid and dry. This applies to the Central Asian deserts of Karakum, Kyzylkum, Gobi and Taklimakan besides the central and eastern parts of the Sahara in Africa. These deserts lie deep within the Asian and African continents and are very far removed from the nearest ocean or sea. But since the size of the continent plays the key role here to create desert conditions rather than dry and hot tropical air, such deserts have a huge range in temperatures – From 40 degrees minus to 50 degree centigrade plus.

The 4th type are the ‘Coastal Deserts’ which are strange in that they are practically without rainfall but are nonetheless relatively moist and cool. Some examples are parts of the Sonoran Desert on the peninsula of Baja California (which falls under Mexico), the Atacama in South America, and the Namib in Namibia (where else) in the South-West part of the African continent. The dryness of these deserts is caused by their proximity to cold ocean currents that run parallel to the coast. These currents ensure that the moist air is carried towards the oceans and the high ground temperatures in the mainland generally disperse the fog and water vapour, thereby preventing precipitation and thus rainfall. It also so happens that all these deserts are on the western side of their respective continents.

Finally we have the very cold ‘Polar Deserts’ of The Arctic and The Antarctic which have some of the lowest precipitation on Earth and hence fit the scientific definition of a desert (a dry and arid place) very well, even if we don’t typically associate the polar areas with deserts.