Fall Equinox 2026: There GOES Summer!
Today is the Fall Equinox in the northern hemisphere and a great opportunity to show off some full disk GOES images. The passing of the seasons has always been marked by humans, sometimes because of agricultural significance, spiritual significance, community bonding, or simply to mark time. The fall (or autumnal) equinox marks the time when the sun is directly above the equator, as we transition seasons from summer to fall in the northern hemisphere (and it’s going from spring to summer in the southern hemisphere). This year the fall equinox is September 22, 2026. It can be seen in GOES visible band imagery at satellite sunrise or sunset where the terminator (the dividing line between night and day) is aligned perfectly north/south in the middle of a full disk visible band image. For the people in the northern hemisphere, the autumnal equinox marks the end of summer and the beginning of autumn, which lasts until the winter solstice (usually December 21). This is the astronomical definition of the changing of seasons as the tilt of the earth on its axis will lead to summer in the southern hemisphere as we head into winter up here in the northern hemisphere.
Sunset and sunrise time-lapse animations from space (below) show the progression of the terminator from spring equinox, through summer solstice, to fall equinox from the satellite’s point of view. For these times of day the disk is “half” illuminated so the terminator formed by the shadow of the night-side of earth is easy to track. GOES-East sits over the equator above 75 West (which is in Columbia, near where the borders of Peru, Ecuador, and Columbia meet) and GOES-West sits over the equator above 137 West (which is out in the Pacific Ocean away from any major land masses – maybe the closest thing is French Polynesia, 680 miles to the southwest; and for reference, Hawaii is over 1700 miles to the northwest of the GOES-West subpoint). These two views provide coverage of nearly two thirds of the earth and so in addition to the terminator you can see some of the things that affected life across our hemisphere from major storm systems to smoke and dust. Technically sunrise, sunset, and local noon vary from day to day, but these animations use a consistent time every day that is close to sunrise or sunset.
Looking back at the past 6 months or so the CIMSS Satellite Blog has been full of interesting cases. We’ve covered: Earth Day, fog, flooding, hail, thunderstorms, tornadoes, tropical storms, volcanic eruptions, wildfires and more!