Monday, September 3, 2007

Seasons in the Sun

My friends in the U.S. might be surprised to learn that September 1 is considered the first day of Spring in Australia. The fact that it’s the “opposite” season from autumn in the northern hemisphere isn't a surprise, of course, but from an American perspective, seasons don’t change until the 22nd. Sometime during elementary school (in Illinois) I had learned the seasons changed during the March equinox, June solstice, September equinox, and December solstice, each around the 21st or 22nd of their respective months. I liked the certainty of those dates, but I really didn’t question whether it made sense to do it this way. In fact, here’s a link to a site where the author examines the logic, but is also apparently unaware that some countries do not observe the beginning of the seasons on these dates because their citizens rely on meteorological, rather than astronomical, reckoning to determine them. Quoting from Wikipedia: “Meteorological seasons are reckoned by temperature, with summer being the hottest quarter of the year, and winter the coldest quarter of the year.

Using this reckoning, the Ancient Roman calendar began the year and the spring season on the first of March, with each season occupying three months. This reckoning is also used in Denmark, the former USSR, and Australia. In modern United Kingdom and Ireland there are no hard and fast rules about seasons, and informally many people use this reckoning. So, in meteorology for the Northern hemisphere:

* spring begins on March 1,
* summer on June 1,
* autumn on September 1, and
* winter on December 1.

Conversely, for the Southern hemisphere:

* summer begins on December 1,
* autumn on March 1,
* winter on June 1, and
* spring on September 1.”

I think this meteorological reckoning actually makes sense, even for the United States. When I lived in the Midwest, it always seemed somewhat stupid to hear on December 22 that it was “the first day of winter,” as I trudged out to the driveway to shovel the snow for the third time since Thanksgiving. Similarly, June 22 is well into summer, especially when you think of Memorial Day and Labor Day in the U.S. as the real bookends to the season.

A final note: I hope that those of you back in the good old USA are having a relaxing Labor Day weekend.

6 comments:

darron said...

We explored the UP of Michigan for the Labor Day weekend. We camped in Marquette County, the largest county in MI for two nights. They had a Blues Fest right on the Lake Superior. They also had a deal going on called "Grandma Doors." They used regular wood doors and put pics and facts about grandma and displayed them along the sidewalk in Marquette(city). We also explored the northern most part of the UP (Copper Harbor). We enjoyed Eagle Harbor the best (the winds were blowing 35 knots). A Coast Guard liaison was making sure a sailboat got back safely to the shore.

Mooselet said...

I want to thank you for that link to Bad Astronomy (a site I've visited before for other things). I always thought it odd the way Australia did it based on merely the first of the month and not an astronomical event. But since I've read that link I'm thinking that waiting until the Equinox is silly.

I guess your work as a teacher is never done! I'll leave you an apple the next time I see you.

The Prof said...

Darron-

Now, that sounds like a real classic American Labor Day weekend! I hope you're going to post pictures on your new blog!

Mooselet-

Yes, my lecturing is nonstop some days...ask my poor wife. Maybe I should have been a tour guide.

Brett said...

Eric, thanks for doing the legwork on the season mystery. I heard a colleague mention spring at work the other day, but didn't think much about it. The first day of spring in Perth this year was nothing to write home about (meteorologically speaking), but the second day...perfection!

Tors said...

Very interesting post. I guess I haven't thought much about the seasons, since we only have 2 up here: Wet and Dry.

The Prof said...

Brett- I hardly heard mention of the "first day of spring" here in Brisbane, but they do seem to note the beginning of summer more prominently.

Tors- What a strange (and wonderful) land you live in! Moving to the tropics must completely affect the way you see the world now. The Wikipedia entry includes a reference to the Wet/Dry distinction, but it's so hard to get my head around that.