Today is the Autumnal Equinox. The term “equinox” means “equal night” and today everyone on planet Earth – from the Poles to the Equator gets 12 hours of day(light) and 12 hours of night…well…not exactly.
Today in Grand Rapids, the sunrise is at 7:29 am and the sunset is at 7:39 pm. That’s 12 hours and 10 minutes. The reasons for that extra 10 minutes are the way sunrise and sunset are measured and the fact that light bends a little bit when it passes through the Earth’s atmosphere, kind of like a spoon in a glass of water looks like it bends when it enters the water. Sunrise and sunset are not measured from the middle of the sun. Sunrise is when the first tip of the sun appears over a totally flat horizon. Sunset is when the last tip of the sun disappears over a totally flat horizon.
The length of day is now 12 hours and 10 minutes. That will shrink to 9 hours and 1 minute (in Grand Rapids) at the Winter Solstice on Dec. 21.
Today the sun will disappear for the next 6 months at the North Pole and appear for the next 6 months at the South Pole.
Here’s a screen grab from the South Pole webcam at 1:50 am EDT. The sky is mostly clear as they await the first rays of the sun in half a year. It’s a bit chilly at the South Pole this morning.
The temperature this morning is a balmy 80 below zero with a wind chill factor of -118F.
The South Pole is colder than the North Pole…and that’s even true on many days when it’s summer at the S. Pole and winter at the North Pole. That’s because the North Pole is at sea level and while the ice there is several meters thick, some “warmth” can come “up” through the ice from the water below. The South Pole sits on land that’s 9,300 feet above sea level.
So far, this month of September has been 3 degrees warmer than average. It’s turned cooler for a few days and the average temperatures do drop at a pretty good clip as we get past the Equinox, but overall we should be a little warmer than average in October.
The latest 8-14 day forecast from the Climate Prediction Center has Michigan and much of the country in the warmer than average area as we close out September and move into the first week of October.