Winter Solstice *

At 12:47 pm today, December 21, 2009, winter begins in the Northern Hemisphere. The first day of winter is called the Winter Solstice; likewise, the first day of summer is the Summer Solstice. The word solstice is derived from Latin and means “sun standing still.” On these two days of the year, the sun’s apparent position in the sky has reached its most southern or northern extreme. Today there will only be 9 hours and 33 minutes of daylight in Richmond, but tomorrow the number of daylight hours will once again begin to increase.
The solstices and the seasons occur because the Earth’s axis is tilted 23.5° relative to its plane of revolution around the sun (see illustration). In the Northern Hemisphere winter, the northern half of the globe is tilted away from the sun; therefore, the sun is low in the sky giving us shorter days and longer nights. At this oblique angle, the sun’s energy is spread over a larger area of the Earth’s surface and thus is weaker than if it was hitting the surface more directly. Also, the sun’s rays must travel through more atmosphere before they reach the Earth’s surface, and some of the solar energy is reflected back into space. In addition, there are less daylight hours to warm the Earth. With all these factors combined, is it any wonder that we have winter weather?
Contrary to what many believe, the Earth is not farther from the sun during the winter. Actually, the Earth is almost at its closest point to the sun at the time of the northern hemisphere’s Winter Solstice. This variation in the Earth’s distance from the sun is small and does not greatly affect the weather; however it does slightly modify the severity of the Northern Hemisphere winters and summers.
While we are experiencing winter, the southern hemisphere is experiencing summer. Our Winter Solstice is the southern hemisphere’s Summer Solstice. If you lived in Rio or Sydney, the winter months would be June through August and the summer months would be December through February.
Here’s some food for thought: what if the Earth’s axis was not tilted? Would we have seasons? What if the axis was tilted more than 23.5°? Or less than 23.5°? What would our seasons be like? How did the Earth get its tilt? All the planets in our solar system have some axial tilt, but they are all different. Why?

*Technical difficulties delayed the posting of this blog entry.

Tis the Season… for Nor’easters?

What will this winter be like? If the current weather pattern continues, the East Coast will certainly be stormy. Friday night through Saturday (December 18-19), Virginia experienced yet another intense Nor’easter (see blog of November 12). This one dumped huge amounts of snow over the central and western parts of the state.
Whether Virginia gets rain or snow from a winter Nor’easter depends largely on the track of the storm. A more westerly inland track will pull in warmer ocean air and Virginia will usually get rain. If the center of the storm stays just off the coast, cold air is often pulled in behind the storm and Virginia can get snow, sometimes lots of it. Nor’easters can intensify to hurricane strength and bring extremely high winds, coastal flooding, beach erosion, and heavy rain or snow to the mid-Atlantic and Northeast states. In the satellite picture above, note the hurricane-like eye in the center of this intense storm.
In addition to the heavy snow and gusty winds, this storm also included thundersnow. Thundersnow occurs only rarely and is basically a winter thunderstorm with falling snow instead of the usual rain. The lightning is nearly blinding due to its reflection off the white snowflakes, and the sound of the thunder is acoustically suppressed by the snowfall. Normally, thunder can be heard many kilometers away from a thunderstorm, but the thunder from thundersnow can only be heard 2 or 3 kilometers away. We had thundersnow at my house just after midnight on the 19th with at least two very bright lightning strikes and accompanying thunder.
How much snow did you get from this storm? I had 1 foot at my house in Midlothian, about 15 miles west of Richmond.

Turkey daze...

Do you fall into a satiated stupor after Thanksgiving dinner? Have you heard that eating turkey makes you sleepy? Turkey contains tryptophan, an amino acid often blamed for the post-meal lethargy. The human body uses tryptophan to make serotonin. Studies have shown that serotonin, a type of neurotransmitter, induces sleep in nonhuman mammals and scientists believe it may do the same in humans. But don’t blame the turkey for your drowsy state. To enter the brain, tryptophan must hitch a ride through the blood-brain barrier on specialized protein transporters. Turkey contains five other amino acids in addition to tryptophan, all vying for a ride. Since tryptophan is the scarcest of the amino acids in turkey, it usually loses out in the competition.
What probably makes you sleepy after Thanksgiving dinner is dessert. Carbohydrates increase brain serotonin even though carbs contain no tryptophan. Here’s how: sweet desserts trigger your pancreas to produce insulin, a hormone that helps cells absorb glucose and amino acids. Insulin has little effect on tryptophan, but it does allow your cells to absorb other amino acids. With the others out of the way, tryptophan catches a ride into the brain and steps up the brain’s production of serotonin. Hence, the urge to snooze…
Even in the absence of dessert, you may find yourself nodding off after Thanksgiving dinner. Loading the stomach with food stretches the small intestine, causing sleepiness. All that blood going to the stomach and intestines means less blood for the brain and muscles. And then there are the beverages. Do you enjoy wine or beer with your meal? Drinks containing alcohol can also cause drowsiness. So enjoy Thanksgiving dinner but please don’t blame the bird for your turkey daze!

Turkey Trivia

1. Top 5 turkey-producing states: Minnesota, North Carolina, Arkansas, Missouri and Virginia.
2. The average American consumed 13.8 pounds of turkey in 2007.
3. Turkey sales are estimated to be $3.8 billion in 2009.
4. Towns named for the bird: Turkey, TX (2008 pop. 456), Turkey Creek, LA (361) and Turkey, NC (272)

Data from the US Census Bureau.

Another helping of cranberries, please...

Did you know, of all fresh fruits, cranberries contain the most phenols, a type of disease-fighting antioxidant? Phenols and polyphenols are strong antioxidants and many scientists believe antioxidants protect the heart. Uncooked berries, dried berries and pure juice are best because processing, storage and heating reduces antioxidant levels, but cranberry sauce still contains lots of antioxidants. So enjoy your extra serving of cranberry sauce…

Which vegetable is #1?

Would you believe it’s the sweet potato? According to nutritionists at the Center for Science and Public Interest, the sweet potato ranked #1 in nutrition when compared to other vegetables. Foods were given points for their content of dietary fiber, naturally occurring sugars and complex carbohydrates, protein, vitamins A and C, iron and calcium. Points were deducted for fat content, sodium, cholesterol, added refined sugars and caffeine. The sweet potato, with a score of 184, easily beat out the second place vegetable, the white potato, by more than 100 points. It’s easy to see why: sweet potatoes have twice the daily allowance of vitamin A, 42% of the vitamin C recommendation and 4 times the RDA of beta carotene. So this Thanksgiving Day, enjoy this yummy and good-for-you treat!

What do you think of this storm? Virginia and much of the mid-Atlantic coast is experiencing a Nor'easter today: heavy rain, gale force winds, coastal flooding, downed trees, power outages, beach erosion... well, you catch my drift. The storm gets the name Nor'easter because the wind blows primarily from the northeast. A Nor'easter is a cyclone, or low pressure system, whose center stays just off the coast. Nor'easters can have winds of hurricane force and can sometimes intensify very quickly.

This particular storm began as hurricane Ida, a tropical cyclone. Tropical cyclones form over very warm ocean waters and get their energy from the release of latent heat when water vapor condenses into water droplets. They have a warm core, no fronts associated with them and have their strongest winds near the surface. Extra-tropical cyclones get their energy from temperature gradients, such as when a warm air mass collides with a cold air mass. They have a cold core, usually both warm and cold fronts associated with them and have their strongest winds in the upper atmosphere. Tropical cyclones can "morph" into extra-tropical cyclones and vice versa, although the latter is more rare.

Many of the worst blizzards in the Northeast US were Nor’easters. Extreme cold often follows in the wake of a Nor’easter, due to cold air being dragged out of Canada by strong northwest winds behind the storm.

The book and movie The Perfect Storm was about an actual 1991 Nor’easter that absorbed Hurricane Grace and later moved far enough south to become a hurricane itself. Unlike most hurricanes, this storm was never named, and New Englanders still refer to it as the No-Name storm.

Did you know surfers love Nor'easters? Waves can be very high during these storms. Even though it is cold, they just don their wet suits and head out.

Do you have a Nor'easter experience? Here's one of mine: my brother had rented a house in the Outer Banks one spring when a Nor'easter hit. Large quantities of sand blew onto and covered the road near Rodanthe. The highway department managed to open a one-lane track for cars to pass, necessitating a wait for oncoming traffic to clear. In the 30 minutes we were waiting, huge hunks of wet sand were raining down on our car. By the time we arrived at the house, the entire left side of the car was caked in sand. That night the house rocked us like we were in a cradle. It was an experience I will never forget.