It’s been a rough winter, and we need spring! We’ve had prolonged stretches of bitter cold with a few weeks of non-stop snow storms. My shovel broke from shoveling so much, and my back isn’t far from breaking, too! We’ll get a step in the right direction Thursday afternoon when spring arrives.
At exactly 12:57pm EDT, the sun’s geometric center shines down on the equator. That is the moment when spring begins in the Northern Hemisphere and Autumn begins in the Southern Hemisphere.
What is an Equinox?
Equinox is Latin for “equal night”, but on this date we don’t have an equal day and night. In fact, the length of the day for March 20th in Providence is 12hours, 8minutes and 45 seconds. The closest we got to an equal day/night was on March 17th when we had 12 hours, 0 minutes and 17seconds of daylight.
Why isn’t there an equal night/day on the day of the equinox? It has to do with a few things. Most importantly, it’s the latitude or how far north/south you are. The shape of the Earth gives northern areas longer days in the spring and summer. For instance Anchorage Alaska’s length of day on March 20th is 12hours, 14minutes and 53seconds (more than 6 minutes longer than the length of day in Providence). Don’t be jealous…they only had about 5 and half hours of daylight in December and the sun was barely above the horizon.
Also, refraction of the light around sunrise/sunset can change the appearance of sunrise/sunset by as much as 6minutes. In addition, sunrise is defined by when the sun’s disk first appears above the horizon; whereas sunset is when the top of the disk reaches the horizon. Equinoxes are determined by the geometric center of the sun, not the top of its disk.
Of course, just because it is astronomical spring, that doesn’t mean old man winter won’t pay more visits. We are expecting a cold last week of March with possibly some snow. Also, history tells us that it can snow pretty good as late as the second week of May here in Southern New England.
The summer solstice is on June 21 at 6:51am….that’s when the sun is directly above 23.5° latitude also known as the Tropic of Cancer.
-Meteorologist T.J. Del Santo