*** Paul Piorek is editor and publisher of Paul's Local Weather Journal for southwestern Connecticut ... Paul is the on-air meteorologist at WICC 600 AM and 107.3 FM ... Paul is a New York Emmy award winner (2007), five-time Emmy nominee, and four-time winner of the Connecticut Associated Press Broadcasters' Association award for Best TV Weathercast (2006, 2008, 2009, 2012) ... Paul was voted Best Local Television Personality by the readers of Fairfield County Weekly Magazine (2012) ... Paul was inducted into the Housatonic Community College Hall of Fame and received the Distinguished Alumni Award (2012) ... The local weather journal is a two-time winner of the Communicator Award of Distinction (2012 & 2013) ... Paul is currently a full-time teacher of Earth Science and Mathematics in Fairfield ... Follow Paul on Twitter @PaulPiorekWICC ...

Monday, September 23, 2013

Fall Foliage I: What Causes the Leaves to Change Color

Ctmansfieldhollow1Today is the first full day of Autumn. This is the first of a three-part series on Fall Foliage in New England. Today, I take a look at why the leaves change colors and what ingredients are necessary for optimum viewing of Autumn’s splendor. The next installment looks at the when the colors reach their peak in southwestern Connecticut and New England. Finally, I’ll explore the best places to view the wide array of colors locally and across Connecticut.

Autumn officially arrived Sunday afternoon at 4:44 p.m. EDT, and it certainly feels like it this morning after a cold front pushed through the region early yesterday. Temperatures fell into the 40s across southwestern Connecticut early today, and Monday night's lows may dip into the 30s inland. Naturally, it’s time to look ahead to what this year’s Fall foliage may bring. Have you noticed any leaves beginning to change color yet? I have. And have you wondered if our weather has cooperated to give us optimum colors this Fall? You’re certainly not alone.

I’ve only noticed just a few trees beginning to show their Autumn colors so far. I’m sure you’ve wondered why the leaves change color. All leaves contain a green pigment called chlorophyll, which is instrumental in photosysnthesis. That’s the process in which energy from sunlight is used to make the sugars that feed the tree or plant. During the growing season, it is continually replaced, but eventually it breaks down.

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As the days continue to get shorter and cooler, the environment is less conducive to growth. Sunset is before 7:00 p.m. now. Photosynthesis, naturally, is suppressed. Chlorophyll continues to deteriorate, and not much is replaced. The rate of breadown increases dramatically after the first frost. The yellow and orange pigments, known as cartenoids, which have been in the leaves all along, become radiant as the chlorophyll levels continue to decline.

Red and purple pigments, called anthocyanins, develop in late Summer and Fall, largely in response to the first frost. These can be seen in some tree species such as red and sugar maples. Leaves with a variety of chlorophyll levels create the colorful landscape that we’ve come to appreciate in the Northeast in the Fall. The shades of color are also influenced by how the pigments interact with other factors in the leaf, including the pH level and what minerals may be present.

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What are the weather factors which ultimately hasten the beauty of the fall colors? The most important factors are sunny, warm days and cool nights. Thus far this month, the average temperature is 67.3 degrees, which is just 0.3 degrees below normal. Eleven of the 22 days this month (50%) have been cooler-than-normal, including a stretch of six straight days from September 14th through the 19th. The warmest temperature was 90 degrees (Sept. 11), and the coolest was 45 degrees (Sept. 18).

Another ingredient necessary for the brilliant colors is rain, and this month has been wetter than normal. Although there have been just seven days with measured rain in September, two of the days featured more than an inch, including September 12 (1.28") and September 22 (1.13"). The total monthly rainfall at Sikorsky Memorial Airport in Stratford is 2.72" which is nearly a quarter-inch above normal. However, no rain is expected this week through the upcoming weekend.

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Too little rain can cause trees to “shut down” early and cause stress for trees. A quick peek at the week ahead shows another splendid week across the Northeast. Today will be mostly sunny, breezy, and chilly with a high temperature in the mid 60s. The rest of the week features slightly moderating temperatures, and no rain is expected through the upcoming weekend.

Paul