It’s Spring! – Sort Of

I love spring and autumn, both because of their milder temps and their beauty. In Texas, spring means the beginning of bluebonnet season. A favorite day trip for Texans and visitors alike is driving the bluebonnet trails around the Hill Country and taking pictures of family and friends in the fields of  bluebonnets and other wildflowers.

As I sat outside this afternoon enjoying the warmer air, the optimistic side of my brain wandered down the avenue of putting my winter clothes into storage and getting out my summer clothes. Then the logical side told me not to because just as sure as I did we would get one final blast of cold air and I would regret not having a pair of sweats or a hoodie.

A little while ago I checked my Instagram notifications and got excited when I saw the picture below. Then the word meteorological registered and it made me pause. I didn’t know there were two different dates for the start of spring.

meteorological spring

Photo from Texas Storm Chasers on Instagram

Google to the rescue!

There is the meteorological spring and the astronomical spring. The astronomical spring this year runs from March 20th thru June 19th. So what’s the difference?

Astronomical seasons are related to the position of the Earth relative to the Sun. Meteorological seasons are related to the annual temperature cycle. The factors that determine seasons are: [Source]

  • the Earth’s rotation around the Sun
  • Earth’s axial tilt (23.5 degrees but it can vary)
  • the Sun’s position over the equator
Solar Declination 2016

Seasonal variation of the declination angle. Courtesy of the UCAR Comet Program. Retrieved from NOAA GOES page.

The Spring (or vernal) and Fall (or autumnal) equinoxes are the times when the Sun is directly over the equator. The Summer and Winter solstices are when the Sun is farthest from the equator (to the North or South.

It is useful to remember that the Southern (austral) Hemisphere experiences the opposite season from the Northern (boreal) Hemisphere (e.g., at the time of writing, it is meteorological autumn and astronomical summer).  Source

I’m going to stop now because that quote got me a little confused. To me opposite would mean that while we in the Northern hemisphere are in winter, those in the Southern hemisphere are enjoying summer. Maybe it’s just the way it’s written that makes it hard for me to grasp. Guess I’ll never be a meteorologist.