Saharan dust: Orange skies and sandy snow in southern Europe | Hacker News Reader

Saharan dust: Orange skies and sandy snow in southern Europe

bbc.com

116 pointspseudolus64 comments

I love the Sahara. I spent one night in the desert and I will never forget it. The stars were amazing. The moon didn't rise until ~midnight. When it did finally rise, I got really confused because I hadn't noticed it missing. At first I thought the sun was rising. I layed on the dunes so long I could watch the stars rotate in the sky.

Watching the stars in a desert is really magical

When the sand falls on the snow in the Alps, it increases the ability of the snow to absorb heat from the sun (because it's darker -- this is known as "albedo") which accelerates the melting of the snow. This happens in the Western United States too, and has been studied [0] as a source of uncertainty in predicting snow melt timing (e.g. for things like water availability).

[0]: https://www.pnas.org/content/107/40/17125.short

This effect is also in play in the arctic, but there it is the dark (compared to ice) sea that absorbs more energy.

Also soot that decreases the albedo of snow. On a smaller scale this effect is also readily visible in just about any city that gets snowfall, especially in the spring!

As a former competitive alpine ski racer, that effect plus the abrasion of the sand itself would make for some very interesting wax choices. “Wetter” usually means a softer wax, but softer waxes don’t stand up to abrasion like that. I’d be interested where the majority of the sand ends up on a mountain and how it gets distributed through the snowpack when groomed out.

Funny, I went through Raytracing In One Weekend[0] recently and encountered the word "albedo" there for the first time in my life. Since then I feel like I've read it or heard it nearly every day! Anyway, thanks for being today's "albedo" guy :-D

[0] = https://raytracing.github.io/books/RayTracingInOneWeekend.ht...

There’s a phenomenon for that called Baader-Meinhof.

https://en.wikipedia.org/wiki/Frequency_illusion

This is very accurate. I spent 10 months in the Saudi Arabian desert as a young airman during Desert Storm in '90-'91. I experienced 3 or 4 sand storms and the enormity of them overwhelmed everything with an orange/tan/yellow hue. I also witnessed sandstorms wear down paint on vehicles to shiny bare metal!!

It's not the first time. [0] This is my picture taken April 3rd 2016 in Poland from Babia Gora mountain.

[0]: http://signalstorm.net/sahara_sand.jpg

Wow, it reaches Poland? I can only imagine what a volcano or an asteroid would cause. I still remember the April 2010 when the Eyjafjallajökull volcano erupted in Iceland causing 100k flight cancellations and a very rainy summer.

Sahara sand likes long journeys: https://www.nasa.gov/content/goddard/nasa-satellite-reveals-...

whoah! I had no idea transatlantic Saharan dust was a thing, let alone that it delivers phosphorous to things growing in South America!

That’s why we’re so fucked if we ever manage to break global weather in such a way that sand doesn’t go from the Sahara to the rest of the world anymore.

Richard Hammond did a pop-science series about the weather and it talked about how dust from deserts can move very far. It's an interesting watch: https://youtu.be/DeYvP2A3QvU&t=8m20s

The dust particles bounce against one another and propel some of the particles higher and higher up into the atmosphere. Then the winds can carry them very far.

Real-time simulation of the Chixculub impact that caused the Cretaceous-Paleogene extinction event: https://youtu.be/ya3w1bvaxaQ

It was quite magical the first time I saw the red dust on my car. I put some of it in a vial, as it came from far, far away.

But as I look around my living room, everything around me comes from even farther, farther away than the Saharan desert.

Were those things in your living room carried by the wind too?

Toto, we're not in Kansas anymore!

Haha, no I think shipping container from Asia.

If they were transported by plane, yes?

January 2020 in New Zealand we had smoke that block out the sky, making everything a weird red hue. The smoke travelled from Australia, 2645km away ( roughly the same as London to Algeria. I was amazed that the smoke could travel that far without dropping off.

I sure felt it made for an ominous start to the decade. I still can't forget that oppressive smoke-cloud with the infrared sun glaring down on us.

It happens relatively often here in the French Pyrenees (it may double down as a Foehn effect going from South to North after passing the ridge line (which is horizontal on a map). If you pay attention, you may notice the result in one James Bond from the Pierce Brosnan era "Tomorrow never dies"; the opening (or second?) scene is supposed to take place in a rogue airbase in Somewheristan, but it was actually shot in an altitude airport in the French Pyrenees, just a day or two after one of those Sahara sand winds.

But this time, it was not just a fine dust. There is plenty glued on the house windows, and shutters, and walls. It was raining mud :-D Never seen that in over 40 years.

I'm 35 and already experienced this mud (in Provence) caused by the Sirocco.

Saharan dust likes to travel, that's for sure.

https://www.nasa.gov/content/goddard/nasa-satellite-reveals-...