Hot, then cold

As extremes of nature go, the marked contrast in temperature of a desert during the day and at night is one of the most impressive. On average, temperatures in Africa’s Sahara Desert can swing an astounding 42 degrees Celsius in 24 hours, rising to an average 38°C with the sun out and plummeting to -4°C after it sets.

What causes this?

Blame the sand. When the sun is out, sand proves to be an effective distributor of heat, reflecting it back into the air. But it’s not very good at retaining heat. Once the sun goes down, heat from the sand is released quickly.

The thing that could help retain warm air overnight is humidity, but deserts don’t have much of that. Water vapour in the air traps heat, preventing either heat or cold from dispersing into the air. Without sun or humidity, daytime heat isn’t being held anywhere, and the desert will cool rapidly.

Why humidity matters

Humidity is also why deserts can feel hotter than other places even though the temperature is the same. The water vapour needs lots of solar energy to heat up, while a dry climate takes that energy head-on.

All of this happens quickly because of that lack of humidity. Just as warm air escapes when night falls, there’s no humidity to trap the chilly evening weather. When the sun rises, it’s back to scorching.

Other factors

Other factors can come into play. Clouds that help moderate temperature and wind can both help keep temperatures from dropping. But generally, you’ll roast in a desert and then freeze because the combination of sand and low humidity isn’t really suited for comfortable and consistent climates.

Man bitten by pet green mamba

The University of North Carolina Rex Healthcare in Raleigh contacted the Riverbanks Zoo in Columbia, S.C., after a man came in reporting that he was bitten by his pet green mamba, a venomous species native to Africa.

“[If] you get bitten by a green mamba without antivenin, your chances of survival are very low,” Sean Foley, curator of herpetology at Riverbanks Zoo, told.

A cooler packed with 10 vials of antivenin was flown via helicopter to UNC Rex, where doctors used four vials to treat the man.

The man is expected to make a full recovery and is back at home with his snake, which is legal to be kept as a pet in North Carolina.

Published in Dawn, Young World, April 17th, 2021