« Return to Thread: there is NO seasonal temperature lag!
there is NO seasonal temperature lag!
by Irv Bromberg
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Dear Calendarists:
I found a web site that posts daily average temperatures for many locations around the world:
... and used their data to make a 2-year plot for Toronto, attached as a small PDF (20 KB).
(Watch out, when there is missing data, they have an entry of -99 as the temperature for the missing date. Also, their data is degrees Fahrenheit, I converted to Celcius.)
The astronomical equinoxes and solstices (from SOLEX) are indicated as vertical lines, at the appropriate position in terms of standard time in Toronto.
To my surprise, and in direct contradiction to Mike's assertions otherwise, in terms of daily average temperature, the actual data shows that there is no seasonal lag -- the chart clearly shows that the maximum average is reached around the time of the north solstice (red), temperature falls off slightly by the time of the southward equinox (brown), the coldest average is reached around the time of the south solstice (blue), and temperature starts to rise by the time of the northward equinox. I checked a lot more years than are shown here (1995-2009 as provided by U Dayton) but the chart is too cramped when it includes the full range. I assure you that the pattern is consistent in any of those years.
(Don't judge the plot in your email client, if it can show PDF images, open it in a PDF viewer application to see the full quality.)
I'm open to suggestions for a limited set of other locales to generate such a plot for. I am thinking about making an Excel macro that could open any of the downloaded files from U Dayton, extract the data from the format that they use (fixed spacing, oddly enough), clear the cells that contain -99, convert to Celcius, and automatically change the chart title to appropriately match the file name (U Dayton uses the file name format XXcity.txt where XX is a two-character country code and city is the name of the location). It would suffice to show the equinox and solstice moments in terms of constant UT moments. It could have scrolling arrows to allow the plotted date range to be scrolled by the user, plot would update in a moment or two. Then anybody could plot whatever locale they want and see what interesting findings emerge. I could be persuaded to make the choice of degrees Fahrenheit or Celcius a user-controlled option. It would be neat to try fitting an appropriate curve, it looks quasi-sinusoidal, although that is not a built-in feature of Excel, my macro would have to carry out the fit. At this point, even though the PDF is only 20 KB, the Excel spreadsheet is 2/3 MB, because it contains all the raw data (has both degrees F and C, doesn't need both).
The point is that the public perception of seasons lagging for some few weeks after the equinoxes and solstices is not based on average temperature but on other perceived factors such as vegetation, blooming, fruiting, harvesting, precipitation, social activities (school vacations), etc. On the other hand, maybe the daily maximum and the minimum temperatures (as opposed to highest averages) aren't reached until the middle of summer and middle of winter, respectively. The U Dayton site doesn't offer that data, as far as I could see. There are different definitions of the "average" temperature. Is it the daytime only? Is it part of the daytime only? Is it the average of hourly temperatures or the average of the minimum and maximum within each day? Ideally (perhaps) it would be based on continuously measured temperature integration for as long as Sun is above the horizon.
Toronto avg temp.pdf (25K) « Return to Thread: there is NO seasonal temperature lag!
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