In these early days of our brand-new year — and by the way, happy new year. 2020 … how did that happen?
OK, as I was saying, in these early days of January, the sun, as seen from earth, is already moving northward after the winter solstice in December. Not only does this give us a much-appreciated increase in daylight, it also plays a role in how high in the sky the sun gets on a given day. By “high in the sky,” I am talking about how many degrees it is above the southern horizon at its highest point in a given day. This is known as solar noon.
I have previously given the formula to calculate how high the sun is in the sky at solar noon for four specific days: the summer and winter solstices and the spring and fall equinoxes. If you missed that, it is ESN (elevation at solar noon) = 90 – (your latitude) + declination. Think of declination as the latitude that the sun is shining directly over on a particular day. For instance, the declination for the winter solstice is -23.5, because on that date, the sun is shining over 23.5 south latitude, also known as the Tropic of Capricorn. (In the equation, latitudes south of the equator are negative, so get a minus sign in front of them.) When the latitude is the equator, on the spring and fall equinoxes, the declination is simply 0.
Presque Isle’s latitude is 46.68 N. Round down to 46.5 N for simplicity. Using the equation, Presque Isle’s sun is 67 degrees above the southern horizon on the summer solstice, 43.5 degrees on the equinoxes (to visualize it, take your arm and hold it straight out in front of you. Let that be the southern horizon. Now hold your hand straight up, like you are asking a question. 43.5 degrees would be about halfway from straight out front to straight overhead. On the winter solstice, the sun is only 20 degrees above the southern horizon at its highest point.
I’ve already given the winter solstice declination, as well as the two equinoxes (above). The summer solstice declination is 23.5 N, also called the Tropic of Cancer.
So, now that you have the equation, ESN= 90 – (your latitude) + declination, you can visit theskylive.com/sun-info#position to get the declination on any day, allowing you to know how high the sun gets in the sky on any day of the year. One nifty way to use this is if you are concerned than an adjacent house to one which you are considering buying, might block your sun at certain times of the year. Well, now you can know.
Incidentally, in earth’s elliptical orbit around the sun, the earth was just at perihelion last Sunday, Jan. 5. At perihelion, the earth is about three million miles CLOSER to the sun than it will be at aphelion, on July 4. It’s the tilt of the earth on its axis as it orbits the sun that is the primary driver of our seasons. In our warm season the northern hemisphere is tilted toward the sun, in our cold season it is tilted away.
One more thing about solar elevation. I’ve always noticed that the sun’s radiant warmth becomes increasingly noticeable as we get deeper into the month of February.
Switching gears, have you ever heard of terrain shadowing? Here’s how it works. Let’s take a nor’easter, so named because the wind direction is typically from the northeast. If there is significantly higher terrain immediately northeast of you, that wind will glide up and then back down to your location. On the upslope side, the precipitation will be enhanced (you’ll get more), and on the downslope side, precipitation rates will be lighter and you’ll get less. So when listening to forecasts for winter storms, it’s always handy to know from which direction the wind will be blowing, as it will inform you whether you could have localized areas of more or less, depending on where you are, relative to the terrain.
Once a winter storm has passed, the wind often increases from the west or northwest, with snow showers on the west-facing higher terrain, while sunny breaks develop on the downslope side.
Oftentimes, ski enthusiasts downstate will head to the western Maine ski resorts following a big snow, and they start out their trip under partly sunny skies…but once they get into the mountains, there can encounter heavy snow showers, reducing visibility, and making travel hazardous. They think, “Hey, I thought the storm was over!”. Well, the region-wide precip part of the storm was indeed over, what they are catching in the mountains is upslope snow showers on a west or northwest wind.
Ted Shapiro holds the Broadcast Seal of Approval from both the American Meteorological Society and the National Weather Association. An Alexandria, Virginia native, he has been chief meteorologist at WAGM-TV since 2006. Email him at tshapiro@wagmtv.com.
