It’s finally warming up! In fact, many people would say that spring is already here, despite the fact that the spring, or Vernal, Equinox hasn’t even happened yet. Astronomers have discovered that the equinox occurs at a specific point in time on a mid-March day, depending on the sun and earth’s alignment, while meteorologists use the word “spring” a little more loosely. Meteorologists note that spring occurs when the weather starts warming up consistently and plants and animals return to continue their growth cycle. A weather oriented spring generally happens two or three weeks before the official equinox. Confusing, right? Why isn’t there just one spring?
Let’s look more in depth at the two different meanings of spring; the astronomer’s version and the meteorologist’s version.
According to astronomers, spring (or fall, depending on what hemisphere you’re in) is the precise moment that the center of the sun passes over the equator, so this year the Vernal Equinox will be officially on March 20, at 4:30am UTC (Coordinated Universal Time). Since a year is actually 365.21249 days and not 365.25 days (accounting for Leap year) long, the time will vary a tiny bit each year, causing the Equinox to fall on one of three days in March, either the 19th, 20th, or 21st.
In Latin, vernal means spring and Equinox means equal night (aequus + nox). Therefore the Vernal Equinox is supposed to be the time in which there is equal amount of day and night. Due to the time it takes for light to reach the earth (8 minutes) and due to light refracting off of the earth’s atmosphere (light gets bent at the horizon point), by the time that the center of the sun passes the equator, there will be more daylight than not, but the spring season will have started.
According to meteorologists, spring is simply when things start getting warmer and coming back to life. Phenology, or the seasonal change and cycle of nature, is the key to understanding this version of spring. Birds have timed their migration back north so that they can nest during the peak of their food source’s growth. Birds may be migrating, leaves may be emerging and flowers may be in bloom.
These things signify to meteorologists that spring has sprung, but it may not be the best way to tell if the season has changed yet or not due to Phenological Mismatch. This occurs when one of these things, such as migration or leaf-out, becomes out of sync with the others. Any disruption to the phenology of plants and animals can have huge impacts on the ecosystem. For instance, due to climate change birds are migrating north earlier, even though the insects that they rely on as a food source aren’t at their peak yet. This can ultimately cause starvation as creating a nest and reproducing requires a lot of energy. Even though birds may be hopping around and singing in our backyard (a reassuring sight, definitely!), spring may not be in full swing. The plants need to come back as well in order to provide food for the animals.
For those of us that aren’t astronomers, it may be hard to tell if the sun has passed over the equator or not, just by looking at the sky, so yes, those “on the ground” signs of spring are important. Keep an eye out for not just the return of birds, but for flower growth such as daffodils, dandelions, and skunk cabbage. These plants provide food for many of the insects that the returning birds eat.
For further in-you-face facts that tell you that spring has sprung, listen to your body! It’s not just plants and tiny fuzzy or feathery animals that undergo seasonal changes. The spring weather triggers a change in the human body as well. Melatonin, the “sleep” hormone is produced when we’re exposed to periods of darkness (nighttime) and more ends up being produced in the winter as the nights are longer. Once spring comes, the days become longer and less melatonin is produced. Heart rates and brain activity also speed up in the spring, causing us to be more energized and distracted. While these symptoms of spring may not be ideal if you’re working in a quiet office environment, but be encouraged and reassured. It’s a sign of warmer weather coming!
For further information, take a look at these links here!
BCAS Instagram Page! We have many pictures of signs of spring around our Visitor Center