ROCHESTER, NY (WROC) – Rochester is fast approaching another milestone this spring season. In just 7 days time our sunsets will begin no earlier than 8 p.m., which means the days are continuing to get longer and ending even later!
As we get closer to summer our sun continues to set later and later, and the northern hemisphere receives increasing amounts of daylight.
How does daylight change year round?
Throughout the course of a year the earth rotates around the sun at a constant tilt of 23.5 degrees. While the earth makes this trek around the sun different parts of the earth receive different amounts of constantly changing sunlight, and is the reason we have seasons.
Fun Fact: The globes that you buy at the store are tilted for this very reason, making them accurate relative to where earth sits in space too!
As we get closer to the summer solstice, which lands on June 20th this year, the amount of daylight we see every day gets a little bit longer. This is because the earth becomes increasingly tilted towards the sun in a way that allows a more direct path of the sun’s energy into the northern hemisphere.
Did you know that the longer the distance light has to travel, the more scattered the light is when it reaches its destination?
This is true as different amounts of sunlight reach the earth at different points of the year. When the earth is tilted at its maximum towards the sun, more sunlight is reaching the northern hemisphere and less is being scattered away in the process since it has less distance to travel through the atmosphere.
Did you know that earth’s orbit around the sun isn’t a perfect circle? It’s actually shaped more like an ellipse, or an oval. This means that the planet spends more time farther away from the sun overall, and therefore receives less sunlight over the course of the year.
The differing amounts of light and energy the earth receives year round is why we have seasons, but the shape of earth’s orbit actually has little to do with it. It’s the earth’s tilt that defines the length of daylight we see, becoming longer from winter to summer, and shorter from summer to winter.
Have you ever noticed looking out your window that the sun isn’t always positioned in the same place at the same time year round? Some parts of the year the sun aligns just right, perhaps when you’re trying to watch the evening news or your favorite show on T.V. and it gets right in your eyes. Then other times of the year the sun has already set and isn’t a bother. That doesn’t happen by coincidence since the sun sets earlier in the winter and later in the summer. The highest point that the sun reaches in the sky each day (what we define as solar noon) is not the same in January as it is in August.
The sun angle is at its highest during our summers, which means we’ll be receiving more light and therefore longer days in just a couple months time. The lower the sun angle, the less solar insolation coming in, and the more the light is spread over a larger surface area. This is why temperatures are warmer in our summer and colder during our winter.
How does daylight change from pole to equator?
Daylight throughout the year is much different at the equator than it is closer to the poles. Since the center of the earth gets the most direct and constant sunlight year round, the change in daylight is drastically different than at the poles. For example, in Quito, Equador which the closest city to the equator gets roughly 12 hours of day and night year round. Barrow, Alaska, located just north of the Arctic Circle sees 67 days of straight night, and over 80 days of straight daylight. This results in very different seasonal experiences throughout the globe. The closer you are to the equator, the less change in daylight and therefore seasons you see.
Time zone affects sunsets too
All sunsets however, are not created equal. Depending on what time zone you live in and which end of that time zone you’re located can affect what time your sun sets. Regardless of which time zone you’re in, the sun will rise relative to earth at the same time in space, but may not be at the same time that your clock says versus someone who lives just few hours west of you.
Time zones don’t line up perfectly with official lines of longitude due to political complications and other reasons. All in all, the farther west you live within your specific time zone, the later your sunset will be. There is a way to calculate how much later the sunsets will be if you’re curious: For every 70 miles you travel to the west, your sunrise will occur about 4 minutes later.
Now that we’re getting into mid April, summer will be here before you know it. Are you counting down the days?
~Meteorologist Christine Gregory