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!
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.
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.
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)
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(*).
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.
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.
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.
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.
This morning is overcast with a 10oF wind chill. I plan to go outdoors … later.
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.
Michigan nurse Lori Marie Key, who went viral singing ‘Amazing Grace’ at work, reprises the song at the national COVID-19 memorial ceremony pic.twitter.com/8OtCaNU5mw
Sunrise on Friday 15 January was a deep crimson red. Though it was sunny for a couple of hours yesterday, gusty wind arrived at 9:30a and rain followed five hours later.
Mackerel sky without rain.
A mackerel sky can predict rain 6-8 hours later, but that wasn’t the case over Frick Park on Saturday 9 January 2021. The day was brilliantly sunny for two hours but became overcast by 5p. These clouds were the leading edge.
Are they a “mackerel sky” or not? What do you think?
Meanwhile, I’d say the bottom right corner is a Harbinger of Gloom.
The desert dips below freezing on winter nights but if you want ice in the summer, how do you get it? This is a story of human innovation using natural processes.
In the 17th century BCE the Persians (Iranians) figured out how to make ice in the desert and store it through long hot summers. They used this method for 3,600+ years until electric refrigeration replaced it in the 20th century.
Though water is scarce in Iran, the method works well because the air is so dry. The process requires many steps: deliver water, make ice, store ice and keep it cool.
Deliver water to the ice-making location: The Persians built underground water channels called qanats to deliver water from uphill wells to the downhill population. Water in the qanat does not evaporate in the sun and stays cooler because it’s underground.
Make ice: To make ice the Persians built plaza-like ponds, shaded by a high wall, where the shallow water froze on winter nights. Collecting the ice before sunrise, they stored it in the ice house (dome in the background). Here are two photos of the same ice plaza no longer in use. People give it a sense of scale.
Store the ice: The ice house, called a yakhchal, stored ice underground, where conditions are naturally cooler, and protected it with an insulated dome. The hole at the top of the dome allowed hot air to escape.
Keep the ice cool: The ice was kept cool using natural ventilation to draw in cold air and remove hot air. Windcatcher towers in some towns were quite ornate.
Here’s a video that puts it all together.
(photos from Wikimedia Commons; click on the captions to see the originals)