Thursday, September 01, 2011

Welcome to Spring

Spring arrived today, and not a moment too soon. I don’t like winter, not even the mild “Winter Lite” that Auckland gets. It still gets too cold for me, without even the payoff of a snowstorm (no, those little flurries last month don’t count).

Our Northern Hemisphere cousins enter autumn this month, though when, precisely, that happens points to a major difference between my two hometowns.

When I lived in Chicago, people always referred to seasons starting on the equinox or solstice (as the case may be), which refers to the astronomical seasons (this year, the September equinox is September 23 at 0905 UTC). Apart from one TV weatherman who pointed out that Chicago’s meteorological seasons didn’t match the astronomical ones, I really don’t remember any dissent from the equinox/solstice dogma.

In New Zealand, it’s the opposite: I can’t think of anyone at all who refers to anything but meteorological seasons, meaning the first of the month (September, December, March and June) as the start of the new seasons. The NZ media talk of nothing else, only mentioning an equinox or solstice in passing, as if observing one is a quaint superstition, like throwing spilled salt over one’s shoulder.

The reality is that whether one adheres to the astronomical equinox/solstice orthodoxy or the meteorological first of the month variant, neither is perfect: Since weather is changeable, the actual arrival of seasons will vary. This is why some meteorologists use other ways than calendars to fix the start of a season, as the Scandinavians who say Spring starts when the average daily temperature is above 0c.

Just to confuse things even more, ecologists often use six-seasons for temperate regions. In addition to the four we’re all familiar with—spring (vernal), summer (estival), autumn (autumnal) and winter (hibernal)—ecologists add pre-spring (prevernal) and late summer (serotinal) as distinct seasons. In the tropics, there are typically two seasons: Wet season and dry season; since the temperature/sunlight varies so little, precipitation is a better indicator of seasons.

In most years, the seasonal changes I’ve lived through have happened in accordance with the meteorological model—close to the first of the month of change, and not some three weeks later.

So, yeah: Welcome to Spring.


Roger Owen Green said...

of course with global warming, it'll be all summer or all winter, all of the time.

Arthur (AmeriNZ) said...

Well, then, to stop that all we have to do is elect politicians who deny it's real and it will all go away. Simple.