MadSci Network: Earth Sciences

Re: What is meant by the term 'meteorological summer'?

Area: Earth Sciences
Posted By: Steve Czarnecki, senior technical staff member, systems engineering, Lockheed Martin
Date: Thu Oct 2 14:17:42 1997
Area of science: Earth Sciences
ID: 875665621.Es

Interesting question, Marilyn. I hadn't heard this term before, but with a little investigation found out how it compares to the usual meaning for "summer".

Astronomers use the solstices and equinoxes to demarcate the seasons. As observers of the sky and historically the calendar-makers, it's natural that they would denote seasons of the year according to celestial configurations. The astronomical definition is by far the most widely known definition for the seasons. September 22 was indeed the end of summer and beginning of fall; more precisely, the change of seasons occurred on this day as the sun appeared to cross the celestial equator around 7:56 pm, eastern daylight time.

Meteorologists, on the other hand, simply declare June, July, and August as "meteorological summer". Not too surprisingly, September, October, and November are "meteorological fall", December through February are meteorological winter, and March through May are "meteorological spring". I suspect this convention simply makes record keeping and climatic data analysis a bit simpler. The definition is not too far off the astronomical definition of the seasons, and it corresponds nicely to our feeling about seasons starting and ending times (at least in our northern hemisphere mid-latitude climate).

By the way, I found a FAQ sponsored by USA Today that answers these and similar sorts of questions about seasons, solstices, and equinoxes. They also have a Web page for Earth Science teachers that you might find useful.

Finally, one last commercial: perhaps you've seen the "Star Hustler" program on your local PBS television station. It's a five minute long weekly program offering tips and explanations for naked-eye astronomy. It typically describes celestial events for the coming week such as interesting configuraitions of the Moon, planets, and stars, folklore surrounding the constellations, etc. I highly recommend the Star Hustler Web site to anyone with even a passing interest in astronomy. The site provides scripts to the various episodes. In particular, several of the provide additional explanation for the equinoxes and solstices, and explains why we call two of the seasons "spring" and "fall".


Steve Czarnecki

(up the road a bit from you in sunny Binghamton, NY)

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