Archive for the 'Weather & Sky' Category

Apr 14 2017

Fewer Mild Weather Days

Published by under Weather & Sky

Mild weather during the Cherry Blossom Festival in D.C., 2006 (photo by Andrew Bossi via Wikimedia Commons)

Mild weather during the Cherry Blossom Festival in Washington, D.C., 2006 (photo by Andrew Bossi via Wikimedia Commons)

Ah, the mild days of spring!  You know the days I’m talking about, the ones that are perfect for birding, gardening, picnics and outdoor weddings.  The not-too-hot, not-too-cold, not-too-wet weather that makes you happy to be outdoors.

Unfortunately Pittsburgh will have fewer of them in the future. That’s what scientists from NOAA and Princeton University found out when they studied how the warming climate will affect our pleasant weather.

The loss has begun already though you may not have noticed it. For the last 35 years (1980-2015) earth’s climate has been converting 1 nice day per year into something unpleasant, mostly in Brazil, Africa and the Middle East.

By the end of the century the change will affect us.  The world will lose 10 mild days out of 74 but the loss won’t be evenly distributed.  The tropics will lose even more mild days while Canada, Maine and the Rockies can look forward to a pleasant future.

Here’s what our future looks like on the map.  Notice how the eastern U.S. is light orange indicating a net loss.

Change in Number of Mild Weather Days by 2090 (map from Van der Wiel/ NOAA/ Princeton)

Map showing the change in the annual number of mild days across the globe comparing 1986-2005 to 2081-2100. Areas of blue have increased in mild days. Areas of brown see a decline. (Van der Wiel/ NOAA/ Princeton)

That map shows the annual change but in fact it will vary by season.  For instance, Pittsburgh will gain some mild days in the fall (maybe 15) but lose more than that in the summer (25 to 50).  June-to-August will be hot!

Changes in the number of mild weather days by season by 2090 (map from Van der Wiel/ NOAA/ Princeton)

Changes in the number of mild weather days by season for 2090 (maps from Van der Wiel/ NOAA/ Princeton)

The full report includes details on mild weather in major cities at: Shifting patterns of mild weather in response to projected radiative forcing.

Now, more than ever, mild weather is a gift.  Enjoy it while you can.

 

(photo by Andrew Bossi via Wikimedia Commons; click on the image to see the original.
Climate map screenshots from Shifting patterns of mild weather in response to projected radiative forcing
)

(*) “Mild weather” is defined as temperatures between 64 and 86 °F, only a trace of rain (less than 0.04 inches) and low humidity (a dewpoint below 68 °F).

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Mar 29 2017

I’m Moving Northward

Carolina chickadee in North carolina (photo from Wikimedia Commons)

Carolina chickadee in North Carolina (photo from Wikimedia Commons)

Last week I wrote about Pittsburgh’s Puzzling Chickadees and promised to tell you why we have fewer black-capped chickadees every year.  The reason is: Our winters are getting warmer.

The Pittsburgh area is squarely in the contact zone where black-capped (Poecile atricapillus) and Carolina chickadees (Poecile carolinensis) meet and hybridize.  Black-capped chickadees can survive cold winters so they live north of the zone.  Carolinas cannot; they live in the south.

The contact zone snakes from New Jersey to Kansas, dipping south along the chilly Appalachian Mountains.  Studies by Robert Curry and his team at Villanova University found that the contact zone is located where winter low temperatures average at or above 14 to 20oF.

In 2010 David Sibley drew the contact zone for his Distinguishing Black-capped and Carolina Chickadees article. Click on the screenshot to see his original map and zoom it for your area.  The map is about 7 years old.

Screenshot of David Sibley's map of the black-capped and Carolina chickadee contact zone in 2010 (click on the map to see the original and zoom it in for your area)

Screenshot of David Sibley’s map of black-capped and Carolina chickadee contact zone approximately 2010. Click on the map to see Sibley’s original article and zoom the map for your area.

 

Seven years make a difference.  During that time the zone moved north almost 5 miles.  Here’s why:

Chickadees don’t migrate but young birds disperse to find a breeding territory.  The easiest territory to claim is an “empty” place where there aren’t competing birds of the same species.  For Carolina chickadees, that place is on the northern edge of the contact zone.

In 2000-2002 and 2010-2012, Robert Curry and his team measured winter temperatures and conducted DNA tests to identify chickadees in study plots north, south and inside eastern Pennsylvania’s contact zone.

The studies showed that over the 10-year period winter average low temperatures moved north 0.7 miles per year. They also found that female Carolina chickadees are dispersing further than their usual 0.6 miles.  They’re moving 0.7 miles northward in lock-step with climate change.

What does this mean for you?

If you live on the northern edge of the contact zone your chickadees can change in a year or two from 100% black-capped chickadees to a mix including Carolinas and hybrids.  On the southern edge it’s just as interesting as the black-cappeds disappear.

So don’t take Pittsburgh’s chickadees for granted.  The contact zone is moving northward.

 

(photo from Wikimedia Commons, map screenshot from David Sibley’s blog: Distinguishing Black-capped and Carolina Chickadees.  Click on each image to see the original.)

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Dec 21 2016

Solstice

Winter sunset at Kuznetsk Alatau, South Siberia (photo from Wikimedia Commons)

Winter sunset at Kuznetsk Alatau, South Siberia (photo from Wikimedia Commons)

By the time you read this, the winter solstice will have passed.

The sun paused it’s southward journey today at 5:44 AM Eastern Time and is already moving north.

Soon the days will be getting longer and the birds will begin to sing.

Listen for the song sparrow.  What day will he sing his first song?

 

(photo from Wikimedia Commons. click on the image to see the original)

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Dec 17 2016

Variably Icy

Icy path in Schenley Park, Feb 2015 (photo by Kate St. John)

Icy trail in Schenley Park, Feb 2015 (photo by Kate St. John)

Snow, sleet, rain, freezing rain.

From 5 degrees F on Thursday night to 53 degrees with freezing rain today, we’ve had it all.  And there’s more to come.  Tomorrow night will be 15 degrees.

This yo-yo weather reminds me of what we learned during the polar vortex in January 2014:  Climate change is making the jet stream wobble so we get shots of very cold air and then warm air soon after, as shown in drawing(c) below.

Jet stream Rossby waves (graphic from Wikimedia Commons)

Jet stream Rossby waves (graphic from Wikimedia Commons)

 

Be careful today!  It’s variably icy out there.

 

p.s. I’ve used an old photo of ice because it’s too icy to step outside this morning!

(photo by Kate St. John.  Drawing from Wikimedia Commons; click on the image to see the original)

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Dec 16 2016

Uh Oh! Blue Light Isn’t Better

 

Uh oh!  Blue light, though bright, isn’t better at night.

As cities switch from incandescent or mercury street lights to LEDs they’re saving electricity and money and providing more light.  But brighter isn’t better if it’s blue.

The video above shows how the color temperature of light matters to our eyes and sleep patterns.  Though the video doesn’t mention it, the color also matters to birds and animals.

It’s possible to buy yellow-toned LEDs but blue, because its bright, has been the default choice for city lights.  We didn’t know that color mattered when the world began switching to LEDs and the bulbs have such a long life it’ll be decades before it’s time to replace them.  Meanwhile humans, birds and animals will be coping with the change.

It makes me want to close my eyes.

 

(video by TOMO news on YouTube)

p.s. Here’s a really helpful video showing the difference between incandescent, compact fluorescent and LED light bulbs in home use (the A19 screw base).  You’ll also see the inside of an LED bulb. I was surprised to learn it’s a tiny computer.

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Dec 09 2016

In 4 Billion Years

Published by under Weather & Sky

 

If you’re planning to be here four billion years from now you’ll see an amazing slow-motion sky show when two galaxies collide — Andromeda and our own Milky Way.

What will the sky look like when that happens? (very amazing!)

Will it be dangerous for Earth?  (probably not)

How many years before this happens?

Billions and billions.

 

(video posted in June 2012 by SpaceRip on YouTube)

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Dec 02 2016

How We’ll See The Stars Again

In my blog two weeks ago, the night sky video Lost in Light made me wonder how we’ll ever see the stars again.

Since then I’ve learned that our outdoor lights waste money and energy, disrupt wildlife, and ruin our own sleep patterns.  What we can do?

The video above from McDonald Observatory shows a simple answer.  Use lampshades.

The quick demonstration below shows why.

 

Right now our cities and towns are switching out incandescent street lights for LEDs.  It’s the perfect time to put on lampshades.    You can shade your home lights, too.

 

p.s. Stay tuned for a future blog about blue light versus red spectrum LEDs.  Yes, the color matters.

(videos from McDonald Observatory and darksky.org)

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Nov 18 2016

We Cannot See The Stars

Published by under Weather & Sky

 

Have you ever seen the Milky Way?

That question would have been absurd 200 years ago because billions of stars were visible on every clear night.

But now with the prevalence of artificial outdoor light most of us cannot see the Milky Way and many children don’t know what it is.

Because of this, some ancient stories don’t make sense.  In Genesis Abraham worried that he had no heir but God reassured him, “Look up into the sky and count the stars if you can. So many shall your descendants be.”   Today we look at the sky and count 50 stars, not realizing that Abraham was overwhelmed.

So what are we missing?  Sriram Murali traveled in California recording time-lapse video of the night sky in places with high light pollution (San Jose) and almost no artificial light (Death Valley).

His video let’s us see the sky as our ancestors did.

Watch the stars come out.

 

(video by Sriram Murali)

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Nov 11 2016

Spring Tide In November

Spring tide Wimereux, France, Sept 2007 (photo from Wikimedia Commons)

Spring tide at Wimereux, France, Sept 2007 (photo from Wikimedia Commons)

Despite the fact that it’s autumn we’re going to have a spring tide next week.

In this case the word “spring” has nothing to do with the season.  Instead it means the ocean will be “springing up” in the highest high tide.

Spring tides occur a day or two after a full moon and are highest when the moon is closest to Earth at perigee.  On Monday the moon will be full and at its closest perigee since 1948.   Watch for nuisance flooding on Tuesday in low-lying coastal communities.

Perigee also makes the moon look larger, an effect called the supermoon.  Here are two photos of the full moon in 2007, perigee on the left on October 26, apogee (furthest) on the right on April 3.

Size comparison of full moon at perigee versus apogee (image from Wikimedia Commons)

Size comparison of full moon at perigee versus apogee (image from Wikimedia Commons)

The difference is about 30,000 miles.  Closer objects look larger.  (Duh!)

If you miss this supermoon you’ll have to wait 18 years for it to be this close again.

Read more about November’s supermoon and spring tide at earthsky.org.

 

(images from Wikimedia Commons. Click on each one to see its original.)

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Oct 29 2016

First Killing Frost?

Published by under Weather & Sky

Frosty leaves (photo by Dianne Machesney)

Frosty leaves (photo by Dianne Machesney)

In the olden days the first killing frost in Pittsburgh usually occurred by Halloween and we had to wear winter coats over our costumes while trick-or-treating.  … I always hated to cover my costume.

This year has been very warm, even hot.  Only ten days ago it felt like August and today the temperature is 5-10 degrees above normal.  When will we experience the first killing frost?

Some of you already have.  If you live east or north of Pittsburgh the growing season is shorter (bluer), as shown on the USDA Plant Hardiness Map below.  Bradford, Pennsylvania is three growing zones colder than Pittsburgh and the Monongahela and Ohio Valleys.  I’ll bet they’ve had a killing frost.

Pennsylvania within the USDA Plant Hardiness Map retrieved October 2016 (map from USDA)

Pennsylvania within the USDA Plant Hardiness Map retrieved October 2016 (map from USDA)

 

Here in Pittsburgh the weather forecast says we won’t dip near freezing for the next several days.  Today it’ll be 10 degrees above normal.

When do you think we’ll have our first killing frost?

 

(photo of frosty leaves by Dianne Machesney, excerpt from USDA Plant Hardiness map at USDA.gov)

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