Frost above zero

Photo: Pixabay

 In Southern Ontario, May 24^th is the traditional day for planting annuals. That’s because the probability of frost after that date is negligible. Not this year. A few days after the 24^th, Environment Canada warned us of the possibility of frost overnight, and they were correct. We had quite a lot of frost damage. The strange thing was that the overnight temperature was predicted to be above zero by a degree or two. I was puzzled because I thought you can only get frost at temperatures below freezing.

 To understand frost, you have to understand dew. Air contains moisture. The warmer the air, the more moisture it can hold. If the temperature keeps dropping, it reaches the “Dew Point” where the air can no longer contain its moisture and water droplets (dew) form out of the air. The Dew Point is dependent on the humidity of the air. If there a lot of moisture in the air, the Dew point is only a little below the actual temperature. If the air is relatively dry, the Dew Point is well below the actual temperature. What if the Dew Point is below freezing? Then we rename the Dew Point and call it the “Frost Point”. When the temperature drops to the Frost Point — you guessed it — instead of water condensing out of the air, frost appears. 

 Back to the mystery of frost when the temperature doesn’t reach freezing. Overnight, as the temperature drops, the ground radiates heat more quickly than the air. So the ground is colder than the air, and the air closest to the ground is colder than air higher up. The fact that cold air is denser and therefore sinks also contributes to the temperature increasing with height. A difference of four degrees between the ground and a height of 1.5 metres would be typical if there is no wind to mix the layers of air. 

 

Stevenson Box. Photo: Metfm, CC BY-SA 4.0, courtesy Wikimedia Commons

 

 

 

And one learning from this is to remember that meteorology is not an exact science.

The "Ew!" Factor

By Claire Eamer

I have a new book out -- and it's so disgusting that it once put my editor right off her dinner. I'm proud of that! (Sorry-not-sorry, Stacey.)

The book is called Extremely Gross Animals: Stinky, Slimy and Strange Animal Adaptations, and it's exactly what it claims to be -- a book about the animals that make you go "Ew!" 

The thing is, once you get past the "Ew!" moment, these animals are fascinating. And adaptation itself is fascinating. 

For example, when I think of mucus, I mostly think of snot and all the unpleasantness that goes with a bad cold or (currently) my over-reaction to pollen in the air. As I blow my nose for the tenth time in a morning, I am not feeling all that friendly about snot. 

But when I learned about some of nature's snot-monsters, I started to change my mind. I'll be honest, I am just as likely as anyone to have a brief "Ew!" moment, but then.... Did you know that snot can be a primo defence mechanism? Or that snot can make a nice, safe place to sleep? Or a vehicle for travelling the world? Honestly, how can that not be fascinating?

And it's all true. Consider the hagfish, a far-from-beautiful eel-like fish with a mouth out of nightmares.

Pacific hagfish poking out of a hole 150 metres below the ocean surface. Credit: NOAA/CBNMS

Then think about picking up a hagfish, or sharing a tank with it as this fellow does. When a hagfish is attacked by a predator -- or even by a television commentator having an "Ew!" moment -- it can produce enough slime (mucus, snot, whatever you fancy) by the bucketful, enough to clog the gills of any fish that fancies it for dinner. Watch here to see some high school students have their own "Ew!" moment at a hagfish research lab at the University of Guelph.

But what about that snotty but safe place to sleep? That's not hagfish, that's the parrotfish, a much prettier denizen of the world's oceans. 

A rainbow parrotfish. Photo credit: Paul Asman and Jill Lenoble

A parrotfish spends its days pottering around coral reefs, eating algae that it has scraped off the coral with its bill-like mouth parts. At night, it sleeps safe and cozy in a cocoon of mucus freshly expelled from glands near its gills. Scientists aren't sure why. After all, you can't interview a parrotfish. However, the cocoon certainly keeps it safe from sharp encounters with coral, may protect it from parasites, and also would give it advance warning of any predator considering a midnight snack of parrotfish.

And the world traveller? Meet the violet sea snail, also called the purple bubble raft snail. 

This violet sea snail washed ashore in Maui with its bubble raft intact. Public domain photo.

As soon as it's born, the snail creates a raft of air bubbles enclosed in mucus to which its single foot is firmly stuck. The snail spends its life floating around the world's oceans upside-down, its foot attached to this mucus-and-bubble raft which keeps it safely at the water's surface. Both "Ew!" and "Awesome!"

And I haven't even begun to tell you what some animals can do with poop. Or puke. Or...well, you'll have to get the book for the rest of the grossness.

Enjoy!

 

Nominees for Red Cedar Book Award!

 This Red Cedar Book Awards have just announced their nominees for the 2020/2021 season. And on this list there are books by two people among the Sci/Why writers!

Boreal Forest by L.E. Carmichael is one of the nominees, and another nominee is Jude Isabella's book Bringing Back the Wolves: How a Predator Restored an Ecosystem. Both books are from Kids Can Press.

  

Red Cedar Book Awards are British Columbia's Young Readers' Choice Book Awards. Click on this link to see the entire list of nonfiction nominees. It's worth saying that ANY of these nonfiction books will make good reading, and most of them are very scientific indeed. You can also see the list of fiction nominees here at this link.