Winter’s Statistical Wonders
As we write, the midwest is being struck by another polar vortex event. We highlight this anomaly and several other annual weather and astronomical phenomena most residents may be unable to explain. The polar vortex, an unusual outbreak of extremely cold “polar” air has its own connection with statistics. The last polar vortex event occurred in 2013/14. In 1977, 1982, 1985, and 1989 our country experienced polar vortex outbreaks, but the term did not become well known until the 2013/14 event. Our family vividly recalls unusual winter events in 1977 and 1982 which weather scientists have now credited to the polar vortex. Unusually rare cold winter outbreaks were described as early as 1853.
Our discussion affirms the complex uniqueness of our terrestrial weather systems. Planet Earth’s weather and weather statistics are far from dull or uninteresting. Our lives exist on a sphere which rotates on its axis and revolves around the sun. The features of our planetary sphere contribute to a fascinating set of interactions. For example, incoming radiation from the sun strikes Earth’s surface at various angles ranging from 90º to 0º. These changing angles result in large variations in solar energy received by the planet.
Ordinarily polar vortexes sit over both poles as high altitude low pressure zones. Winds circulate around them toward the east. Our northern hemisphere vortex becomes stronger in winter, usually as a single vortex. On occasion it weakens, becomes more disorganized, and sends atypical pockets of intensely cold air as far south as the northern tier of the United States. Temperatures lower than 30º below normal could result. These unusually cold outbreaks have resulted in all-time record cold temperatures. The Book of Job documents such events. In chapter 38 the Lord spoke about many aspects of the awe-inspiring world he created: “From whose womb comes the ice? Who gives birth to the frost from the heavens when the waters become hard as stone, when the surface of the deep is frozen?” (Job 38:29-30 NIV) The Creator knew of the polar vortex before any man explained it and assigned its modern name.
We continue our “statistical wonder” post with mention of three more ordinary weather and astronomical phenomena: (1) Sunrise and sunset times—how they differ at various locations, (2) latest sunrise and earliest sunset times throughout the year, and (3) the date of the “coldest day” and “warmest day” of the year. (As an aside, we mention that many statistical facts are reversed in the southern hemisphere.)
Sunrise and sunset times at any location—Everyone has had phone conversations with someone in a distant location when one party is in sunlight and the other is in darkness. No doubt your phone partner was one or two time zones away—for example, 7 PM at your location, 9 PM at their location. Within any single time zone on a given date, the time by the clock is identical, but sunrise and sunset events for residents of that time zone occur at different times by the clock. To illustrate, statistics from December 7 reveal that four cities on an east to west strip passing through our home town (Chicago IL, Rockford IL, Dubuque IA, and Des Moines IA) had sunset times of 4:19 PM, 4:24 PM, 4:29 PM, and 4:44 PM respectively. These facts could enable young students to prove that we live on a spherical planet.
Latest sunrise and earliest sunset times—Statistics of sunrise and sunset times on every day of the year are easily accessible online for virtually every city in the world. One would think that the shortest day of the year would also correspond with the earliest sunset paired with the latest sunrise. But the earliest sunset precedes the shortest day of the year by about two weeks. The latest sunrise actually occurs a similar amount of time later than the shortest day. Astronomy articles sometimes highlight this unexpected phenomenon. In order to spare our readers from a lengthy esoteric discussion, we are content to affirm that the Earth’s obliquity (tilt on its axis) and it’s ellipticity (the degree of deviation from the circular) both affect sunrise and sunset times. Our world provides many fascinating surprises.
Last, we discuss why the coldest day of the year is not the shortest day of the year, and why the warmest day of the year is not also the longest day of the year. On the shortest day of the year (according to how long the sun is above the horizon), the coldest day of the year is still more than a month away. The longest day of the year (according to the sun) occurs before the warmest day of the year by a similar time interval. Coldest and warmest temperatures are statistically reported as average mean temperatures determined by studying records from many years in the past. Temperature on any given day at a given location is related to the amount of heat energy received balanced by the amount of heat energy lost.
Average temperatures increase over time because the earth receives more heat energy than it loses. When average temperatures decrease the earth is receiving less heat than it loses. On a seasonal scale we are dealing with “seasonal lag.” Many factors relate to this lag, including the fact that land and water bodies absorb and release heat energy at different rates. This is not only a seasonal phenomenon acting over long time frames, but also a daily phenomenon acting over short time frames.
My paternal grandfather, a lifetime farmer in New York State born in 1880, observed that “winter’s back is broken” when the winter temperature commenced its very slow rise about January 25, about one month after the shortest day of the year—December 21. He observed that afternoon sunsets became noticeably later even though the daily temperature had not yet risen significantly. He must have looked forward to the beginning of his annual maple syrup-making activity which was to begin later in February, long before winter was finished with its assaults. We quote from a yellowed newspaper clipping from the Baldwinsville, NY Messenger of March 17, 1955: “Mr. Virkler thinks that he would feel lost if he didn’t get the sap buckets and spiles out each February and begin making the rounds to the big sugar maples that line the road side and driveway of the farm.”
I was raised two houses away from the 150-acre farm on which my grandfather operated his “sugar bush” for several weeks in the late winter and his dairy farm for the remaining weeks of the year. The farm was a wonderful venue for observing weather events and the wonders of plant growth and animal life. His children and grandchildren learned to appreciate the astronomical, meteorological, and agricultural wonders authored by the Creator of All Things. Perhaps the polar vortex which has descended on the midwestern US as I write the current post may have been the subject of the Lord’s reminders in Job 38:29-30.