“Time And Tide Wait For No Man.”

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That quote is from Goeffrey Chaucer and it has been used in many different situations. This time it has meaning for two situations. If you pay attention to your calendar you probably noticed that the Vernal Equinox is fast approaching and so is the changeover to Daylight Saving Time. As a matter of fact both events occur on the same day March 14, 2021. The Vernal Equinox marks the beginning of Spring in the Northern Hemisphere.

Vernal Equinox3
Vernal Equinox3 | Image by earthsky.org

We all remember being taught about Equinox and Solstice events in school, but how many of us actually remember the details today? That’s why I am going to explain it in detail now.

Here is the definition of the Vernal Equinox according to an article in Astronomy Essentials by Deborah Byrd posted on earth sky.com: The Vernal Equinox “signals the beginning of spring in the Northern Hemisphere and autumn in the Southern Hemisphere. It marks the special moment when the sun crosses the celestial equator going from south to north.” Equinox translates as “equal night” which means the length of day and night is nearly equal all over the world during the equinox.

Vernal Equinox2
Vernal Equinox2 | Image by heimhenge.com

It all has to do with the earth’s axis. That’s the reason for the seasons. As you might remember the earth’s axis is tilted and not parallel to the earth’s orbit. According to the meteorology text book The Atmosphere by Anthes, Panofsky, Cahir, and Rango “There is an angle between the plane of the equator and the plane of the earth’s orbit (also called the ecliptic). This angle, which has the impressive name obliquity of the ecliptic, is now 23 1/2 degrees.” “As the earth revolves about the sun, it’s axis points in the same direction in space.”

Solar Rays
SolarRays | Image by lpi.usra.edu

Both the northern and southern hemispheres get exactly the same amount of sunshine during the two equinoxes, March 20-21 and September 22-23. The authors explain that over tens of thousands of years this angle has changed, and, as a result, the severity of the seasons has also changed. The seasons are less harsh when the angle is small and conversely they are more harsh when the angle is large. Over the last 100,000 years or so the angle has varied between 22 and 25 degrees because the earth actually rocks back and forth a bit as it continues it’s march around the sun.

Solar Rays At Equator
Direct Solar Rays At Equator | Image by Annenberg Learner

At the Vernal Equinox the rays of the sun are directed straight at the equator and then move northward continuing the spring warming and then bringing on summer, the warmest time of the year.

Sun Ray Angles
Solar Ray Angles | Image by physics.weber.edu

One would think that the direct straight-line rays of the sun when the distance between the earth and the sun are at their closest would make the area under them see the warmest time of the year but that is not the case. There is a space of about 3 months between the Vernal Equinox and the warmest days of summer.

Daylight Saving Time
Daylight Saving Time Clock | Image by 1011now.com

Daylight Saving Time is when we “Spring Forward” by turning our clocks ahead by one hour at 2:00 am Sunday March 14th or at bedtime Saturday night if you are not a stickler for being perfectly accurate and don’t want to stay up until 2:00 am to change your clocks. Most of the newer appliances and electronic devices make the change automatically, but the older models must be changed manually which can be a pain. The authorities tell us that we should also check our smoke alarms, Carbon Monoxide detectors, and Radon detectors to make sure they are in working order. Replace batteries if necessary.

Oregon lawmakers passed a bill in June 2019 to keep Oregon on Daylight Saving Time all year long. The Governor signed the bill one week later, but we still went back to Standard Time November 1, 2020. It is possible that we will have made that changeover for the last time, but we’ll have to wait for an official announcement that the change is really final.

Let me know what you would like me to talk about or explain. You can comment below or email me at: [email protected].

Tim Chuey is a Member of the American Meteorological Society and the National Weather Association and has been Awarded Seals of Approval for television weathercasting from both organizations.

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