Category Archives: Weather & Sky

Air Then and Now

50 million year-old spider and air trapped in amber (photo from Wikimedia Commons)

22 April 2021

If you want to know what the air was like 100 million years ago, look at the air trapped in amber. In 2013 scientists analyzed 538 samples and discovered that in the age of the dinosaurs there was less oxygen in the air than now. The concentration in the early Cretaceous period was only 10-15% compared to 21% oxygen today. It was similar to the available oxygen at Mount Everest Base Camp.

If you want to know what the air is like now in the U.S. check the 22nd annual State of the Air Report issued yesterday by the American Lung Association (ALA). Sadly, Pittsburgh is still in the top 10 of Bad Air cities for year-round particle pollution.

The State of the Air Report doesn’t even measure the rotten egg smell — hydrogen sulfide, H2S — that’s produced by U.S. Steel’s Clairton Coke Works and Edgar Thompson Works in Braddock.

High concentrations of H2S (widely recognized by its foul, rotten-egg odor) are registered all too often in the Mon Valley. In fact, so far this year there have already been 21 exceedances of Pennsylvania’s 24-hour average H2S standard – 13 at the Liberty monitor and eight more at the North Braddock monitor., State of the Air Report, 21 April 2021

This month has been especially bad. Here’s what it looked like last Sunday 18 April on Smell PGH’s crowd-sourced bad smell report.

In Pittsburgh, the nose knows.

That rotten egg smell (Tammany cartoon via Wikimedia Commons, text removed)

Read more about the air the dinosaurs breathed in this vintage blog: Ancient Air.

Read more about Pittsburgh air quality (Pittsburgh area air quality still gets failing grades) and what you can do about it at the Group Against Smog and

p.s. The scientific paper about the air-in-amber research is here:

(photos from Wikimedia Commons, Smell PGH screenshot from the app; click on the captions to see the originals)

Cleared For Take Off?

Volcanic eruption plume of La Soufrière, 9 April 2021 (photo from Wikimedia Commons)

21 April 2021

Twelve days ago Saint Vincent’s La Soufrière volcano began erupting after four decades of silence. Since 9 April it has blanketed the island with thick ash, forced the evacuation of 20,000 people, and ruined fresh water, homes, and farms. It has also caused a deep humanitarian crisis (see 5-minute British Channel 4 video at bottom) and killed untold numbers of local plants, animals and birds.

map of Saint Vincent and the Grenadines in the Caribbean (Wikimedia Commons)

The volcanic plume is also devastating the air, bad to breathe and dangerous for anything that flies. Saint Vincent’s airport closed when the eruption began while NOAA’s Volcanic Ash Advisory Center provides maps of Caribbean no-fly zones for pilots. The 10 April zones match the plume graph from NASA.

NOAA VAAC maps, Saint Vincent
Tracking La Soufrière’s plume (image from NASA Earth Observatory)

Though the disaster feels far from Pennsylvania it may affect our migratory birds that have not yet crossed the Caribbean from South America. Will the birds smell the plume and find a way to avoid it?

Airplanes will soon be cleared for take-off at Saint Vincents airport. I wonder if the birds will be, too.

This 8-minute video from Britain’s Channel 4 shows the devastation at Saint Vincents.

p.s. Click here for a video of satellite imagery showing the atmospheric effect of La Soufrière volcano.

(images from Wikimedia Commons, NOAA and NASA Earth Observatory)

The Worm Moon is The Crow Moon

American robin pulling up a worm (photo from Wikimedia Commons)

27 March 2021

You may have heard that tomorrow’s full moon at 2:50pm EDT (28 March 2021) is called the Worm Moon after the earthworm casts that appear as the ground thaws.

Did you know it’s also called the Crow Moon?

The more northern tribes of the northeastern United States knew this as the Crow Moon, when the cawing of crows signaled the end of winter.

NASA: The Next Full Moon is a Supermoon Crow Moon

Northern tribes didn’t have worms where they lived because the Ice Age wiped them out. Instead they noticed the change in crow behavior.

Nowadays we have earthworms that were accidentally imported from Eurasia so the Worm Moon makes sense to us.

In Pittsburgh the Crow Moon happens in December. 😉

Crows silhouetted against the supermoon, December 2017 (photo by Kate St. John)

Read more at The Next Full Moon is a Supermoon Crow Moon.

(photo from Wikimedia Commons and by Kate St. John)

Sights and Sounds of Early Spring

Sun pillar at sunrise, 6 March 2021 (photo by Kate St. John)

14 March 2021

Spring is coming! Our native trees are slow to bloom but cultivated flowers and amphibians are already active. There’s a lot to see and hear.

Above, on 6 March we were greeted by a sun pillar caused by ice crystals slowly falling through the air at sunrise.

A shagbark hickory lives up to its name in bright sunlight.

Shagbark hickory, Raccoon Wildflower Reserve, 12 March 2021 (photo by Kate St. John)

American basswood now has bright red buds that are still cautious about opening.

American basswood buds, Raccoon Wildflower Reserve, 12 Mar 2021 (photo by Kate St. John)

Cultivated European white willows have bright yellow twigs in March.

Cultivated willows turn yellow in early spring, Homewood Cemetery, 9 Mar 2021 (photo by Kate St. John)

Non-native crocuses are blooming so I hoped to see native snow trillium at Raccoon Wildflower Reserve on Friday, 12 March 2021. I did not find any, not even leaves. Was I too early or did the deer eat them?

However I was rewarded with the sound of frogs! Spring peepers and a few wood frogs called from the first vernal pool.

Peepers calling at Raccoon Wildflower Reserve, 12 March 2021

Wood frogs quacked in the second pool joined by a few solo peepers (hear that slow “creeeek” sound). In the video you can see the surface of the water moving with so many wood frogs.

Get outside while the sun’s shining. There’s more spring to come!

(photos audio and video by Kate St. John)

A Chunk of Comet Killed the Dinosaurs

Incoming! The event that killed the dinosaurs (screenshot from Harvard University video)

24 February 2021

Ever since the early 1980s when Luis and Walter Alvarez discovered that the Chicxulub Crater in the Yucatan and the extinction of the dinosaurs were caused by the same event, we’ve talked about the “asteroid” that killed the dinosaurs. Recently two Harvard researchers took a new look at the composition of Chicxulub rocks and the physics of comet behavior and revised that conclusion. It wasn’t an asteroid that killed the dinosaurs. It was a chunk of comet!

Asteroids live in the main belt of the inner solar system located between Mars and Jupiter. Comets are from the Oort cloud of interstellar space.

Logarithmic scale distance of the Oort Cloud from the rest of the Solar System. Voyager 1 location in 2013 (image from Wikimedia Commons)

The video below explains how a piece of comet could break off and cause the Cretaceous–Paleogene extinction … and how soon one could hit us again. By the way, Jupiter is involved.

Yow! Oh no!

Illustration of an unusual association of hadrosaur and therizinosaur from tracks found in Denali National Park, Alaska (illustration by Karen Carr via Wikimedia Commons)

A chunk of comet killed the big dinosaurs. Fortunately we still have the little ones with us … Birds!

(screenshot at top from Harvard University video, remaining photos from Wikimedia Commons; click on the captions to see the originals)

Will We See A Moon Ring This Winter?

22 degree halo around the moon, Croton-on-Hudson, 30 Dec 2020 (photo from Wikimedia Commons)

30 January 2021

In winter when the moon is full and the sky is almost clear with a thin layer of cirrus clouds you may see a halo around the moon. The ring has a radius of 22o so it’s called a 22o halo, a moon ring, or a winter halo.

The conditions for a moon ring are relatively rare in Pittsburgh: a full moon + a clear sky + thin cirrus clouds whose ice crystals refract and reflect the moonlight. Seeing the halo is a matter of perspective based on where you stand and which ice crystals refract/reflect for you.

That’s why, like rainbows, halos around the sun – or moon – are personal. Everyone sees their own particular halo, made by their own particular ice crystals, which are different from the ice crystals making the halo of the person standing next to you. “What makes a Halo Around the Moon”

On Wednesday night, 27 January, the nearly-full Wolf Moon rose before sunset hidden by Pittsburgh’s overcast sky. By 8pm the clouds were breaking up and made an iridescent halo around the moon. It was not a true 22o halo but it cast enough light to make shadows. All I have to show for it is this very blurry photo.

Fuzzy photo of full Wolf Moon with iridescent cloud ring, Pittsburgh, 27 Jan 2021 (photo by Kate St. John)

The next morning at 4:15am the sky was absolutely clear and the moon was shining brightly without a ring. I was disappointed because the clear sky was wasted on us while Pittsburgh slept. Three hours later the sun rose in an overcast sky.

Last night was the same — a nearly full moon and an absolutely clear sky. No moon ring.

The Wolf Moon is waning and winter will too. The next full moon on 27 February is our last chance at a Winter halo. The full moon after that — 28 March — will be in the Spring.

(photo at top from Wikimedia Commons; click on the caption to see the original. blurry photo by Kate St. John)

Seven Years Ago: Snow Rollers

Field of snow rollers, Clarion County, PA, 27 Jan 2014 (photo from Wikimedia Commons)

28 January 2021

Seven years ago this week open fields in eastern Ohio and western Pennsylvania were graced with a rare winter phenomenon. Snow rollers!

Snow rollers are delicate snow balls made by the wind that look like snow bales or jelly rolls.

Snow roller, Newark, Ohio, 30 Jan 2014 (photo by Mary Ellen St. John (no relation) via Wikimedia Commons)

They can only happen when all of these weather conditions are met.

  • First an icy layer(*) forms on top of old snow that new snow will not stick to.
  • Then, a thin layer of wet, loose snow falls on the ice.
  • After the wet snow falls, the wind blows just hard enough to start the balls rolling without destroying them.
  • Snow rollers stop when they are too heavy for the wind to move. 

The center of a snow roller, the first layer, is fragile and disintegrates easily. Even before a snow roller becomes hollow it is too fragile to pick up.

Snow rollers, Clarion County, PA, 27 Jan 2014 (photo from Wikimedia Commons)

This year it’s too warm and we have don’t have much snow so I doubt we’ll see snow rollers any time soon.

Read about 2014’s rare occurrence in this vintage article: Nature’s Snowballs.

(photos from Wikimedia Commons; click on the captions to see the originals)

(*) In other climates snow rollers can form on top of powder snow and can be triggered by a snowball falling on a steep hill.

Speaking of Clouds …

Clouds and blue sky above Nine Mile Run, Pittsburgh, 11 Jan 2021 (photo by Kate St. John)

25 January 2021

During Pittsburgh’s overcast winters we grumble about clouds and pray for sunshine. On Saturday after blogging about last week’s clouds, I was outdoors with Liz Spence when the clouds broke at 1pm. “Look! We have shadows!”

For real excitement, though, check out these lenticular clouds over the Rincon Mountains in Tucson, Arizona, 18 January 2021. We never see this in Pittsburgh(*).

(*) because we don’t have mountains. Read more here about lenticular clouds.

(top photo by Kate St. John)

Keyholes and Clouds

Through the garden gate at Phipps Conservatory, 17 Jan 2021 (photo by Kate St. John)

On overcast days it’s too easy to convince myself not to go outdoors but last week, when five of seven days were overcast, I forced myself to walk to Phipps to take photos of dawn redwoods. While there I looked through the garden gate — like a large keyhole.

On the 20th I promised myself to be at Schenley Park Overlook at noon for a big view of the sky, the city and the Cathedral of Learning (falcon home). On the way there I snapped a photo of Panther Hollow Lake, surprisingly shaped like a giant keyhole.

Panther Hollow Lake, normal water level, 20 Jan 2021 (photo by Kate St. John)

The day ended with a Gleam At Sunset, 10 minutes of happy sunshine before darkness. Below you can see the source of the gleam, a patch of clear sky in the lowest notch between the buildings.

The Gleam at Sunset, Pittsburgh PA, 20 Jan 2021 (photo by Kate St. John)

Working backwards in time, 19 January provided a welcome respite with a panoply of blue sky and clouds. One cloud broke away from the pack.

One cloud above the hill, Pittsburgh PA, 19 Jan 2021 (photo by Kate St. John)

January 16th was gloomy with freezing fog, light snow and mist but two merlins and The Gleam At Sunset made my late-day walk to Schenley Park worthwhile.

The Gleam at Sunset, Schenley Park, 16 Jan 2021 (photo by Kate St. John)

This morning is overcast with a 10oF wind chill. I plan to go outdoors … later.

p.s. I digitally brightened the gloomy skies in yesterday’s blog.

(photos by Kate St. John)


Sunrise over Joshua Tree, California, 2011 (photo from Wikimedia Commons)

20 January 2021

Little did we know a year ago today when the first known case of COVID-19 was reported in the U.S. that we were heading for a year of recurring fear, illness, death, isolation, political unrest and economic hardship. By now almost everyone knows someone who tested positive. Too many know someone who died.

Yesterday the U.S. COVID-19 death toll reached 400,000. To put this in perspective, that’s the entire population of Tulsa, Oklahoma or Tampa, Florida or 1/3 of Allegheny County, Pennsylvania.

For a year we have been grieving alone or in small groups. Yesterday for the first time we mourned as a nation for the lives lost to the coronavirus. A nurse from Livonia, Michigan who cares for COVID patients sang Amazing Grace as a tribute to those we’ve lost.

We’ve been going through a very dark time but we can work together for a brighter future.

Today let us take solace in the beauty of nature and begin to hope.

(video by Terje Sorgjerd at El Teide Mountain, Spain, April 2011; music by Ludovico Einaudi)