The Canicula and Extreme UV Index

[Really full garden]

In Guatemala we have what is known as the Canicula . This is a dry period during the rainy season that can last a few days or a month. This year it came earlier and we also have haze from the sand blowing in from the Sahara . We are also having extreme UV index 14+ .

I have noticed some normally very beach tolerant palms showing some burn despite abundant irrigation.

 

 

[palmsOrl]

UV index of 14!  What is the highest ever recorded and the highest theoretically possible UV index I wonder?

Nice to put a name to those irksome dry periods in the middle of our rainy season.  Canicula.

[palmsOrl]

...and the answer is: 43.3 UV index recorded at the top of Bolivia’s Licancabur volcano in December 29, 2003, due to a combination of exacerbating factors.

[Really full garden]

At 14 you can feel a burning sensation on bare skin after just a few seconds.

Imagine palm fronds exposed for many hours!

[kinzyjr]

And I thought a UV index of 11 was skin cancer waiting to happen...

[DeletedAccount14e83d09a24f]

2 hours ago, kinzyjr said:

And I thought a UV index of 11 was skin cancer waiting to happen...

hahaha, pretty much the same as me. And it is, under UV 11 you're at extreme risk. Any outdoor activity from 12 to 4 PM is strongly not advised!

[tropicbreeze]

You can't feel UV radiation from the sun. What you feel is the thermal radiation which can get blocked by cloud cover. UV radiation is little affected by clouds so in cloudy conditions you can be lulled into a false sense of security. During periods of higher UV radiation, with or without cloud cover you still need to protect yourself.

[Silas_Sancona]

7 hours ago, Alicante said:

hahaha, pretty much the same as me. And it is, under UV 11 you're at extreme risk. Any outdoor activity from 12 to 4 PM is strongly not advised!

This time of year here, any watering / other chores to be done outside are done before 10am, or after sundown ( 7:40-ish pm currently ) Our UV index also seems to top out at 11 though I myself think it should be closer to 13 right about now. As thick as FL / monsoon season humidity can make it feel at times, i dare anyone to work outside thru a summer here when it's as dry and toasty as it is right now.  You'll wish for that kind of buffer from the sun..  Never thought I'd prefer humid heat over the "drier" version, lol.

Edited July 7, 2019 by Silas_Sancona
Edit

[Daryl]

During our summer here, we regularly see UV over 13, and the highest this year was almost 16. In Nth Qld and the NT, it is consistently higher than here.  During these times it is very hot and  humid in these areas and even with the humidity a lot of plants (and humans ) burn very easily.  The surface temperatures of exposed leaves are very high, and I think this is the main culprit.   As Tropicbreeze mentioned above,  even when it is cloudy it is bad, and because the sun is not directly cooking your skin, you expose yourself to slightly lower UV levels for much longer times, so end result is much greater exposure and the 'Lobster' effect if you didn't take any sun-care precautions.  Unfortunately for our poor plants they just have to deal with it...resulting in leaf burn...and those leaflets held more horizontally tend to burn more than droopy leaflets...just some of my observations over the years...

I remember as a kid, helping my dad with his Met observations...one device I thought was cool was this...the old fashioned way to measure sunlight hours....burning a piece of cardboard with a glass sphere...

 

Campbell Stokes Recorder

 

[Really full garden]

Today there is a definite change. Its cooler,cloudy and the tropical convergence zone has moved further north where it normally is.