Wonders of the winter solstice
By Jared Shelton News-Press NOW meteorologist
Meteorological winter arrived several weeks ago, but the winter solstice marks the “official” or astronomical start of the season. This benchmark in time reminds us of the tilt of Earth’s axis, driving seasonal changes across the globe through its year-long orbit around the sun.
Opposite to the summer solstice, also known as the longest day of the year, the winter solstice is the shortest as the least amount of daylight strikes about half of Earth’s surface. In the northern hemisphere, the winter solstice occurs between Dec. 21 and 23, depending on the year. During this time, the North Pole is tilted farthest from the sun. By definition, that also includes everywhere north of the equator.
This year’s winter solstice is due on Saturday, Dec. 21. Here in St. Joseph that means only nine hours and 21 minutes of daylight, a small change from the day before but a far cry from the 14-plus hours we enjoy in mid-summer. The good news is days will only grow longer after the solstice, as earlier sunrises and later sunsets ultimately lie ahead.
For this reason, the winter solstice has been celebrated by several ancient civilizations as a “rebirth” of the sun. Interestingly, the famed Stonehenge in England was even built to help capture the solstices. The sun centrally aligns with the structure when it rises on the summer solstice and sets on the winter solstice. Thousands will gather at Stonehenge this Saturday to continue the ancient celebratory tradition by observing the sunrise within the circular structure marking the start of the winter solstice.
The darkest days of winter will be behind us by Dec. 21, but the coldest air of the season will certainly not be. Mid-January is climatologically the coldest part of winter in the Midwest and much of the United States. Average temperatures in St. Joseph range from the upper 30s to mid-teens during this time, and periodic outbreaks of arctic air often allow the mercury to plunge into single-digit and subzero territory for several days or even weeks at a time.
The disconnect between hours of daylight and global temperatures is called seasonal lag. Landmasses, bodies of water and ultimately Earth’s atmosphere take about a month to respond fully to the maximum decrease in solar radiation. This is part of the reason for meteorological seasons, which align more closely with seasonal weather changes rather than astronomical benchmarks.
