What happened September 2nd? A registrar’s climate mystery
Part 2 – The Hint

what_happened

I had a look at the graph. It looked like a pretty normal day in this area until about 16:40. We have a slow increase in temperature from about 21 degrees to 25 degrees Celsius (69,8 to 77 degrees Fahrenheit) and a drop in humidity from 60% to under 50%. Nothing odd for this less-than-ideal hall in the changing season of a German autumn. If you take a look at the weather dates of said day from the nearby weather station you can see that our inside correspondents with the outside: http://archiv.mannheim-wetter.info/2013/pcws/20130902.gif (thick green line for temperature, thin purple line for humidity).

Then, after 16:40 things got odd. We see a sudden increase in temperature up to 29 °C (84 °F) and a drop from 44% to 23% within only 10 minutes. If this weren’t odd enough, only 20 minutes later we see the temperature dropping back again to 25 °C (77 °F) and humidity slowly increasing to 32%. At 17:30 we see again an increase in temperature, climbing up to over 30 °C (86 °F) and staying as high until 19:00 to slowly, slowly start decreasing over the next few hours, reaching 13 °C (55,4 °F) at half past seven the next morning. Then, suddenly, the temperature increases, again in an unusual way, reaching 16 °C (60,8 °F) at 7:40, nearly 19 °C (66,2 °F) at 7:50, peaking to 22,5 °C (72,5 °F) at 8:10 to become quite stable again at 21 °C (69,8) and 57% relative humidity.

Again and again I looked at the data and discussed it with colleagues. Then, a colleague mumbled “Looks like trouser pocket.”

Suddenly I could see the whole story when looking at the graph. Can you?

The Start
The Solution

This post is also available in Russian translated by Helena Tomashevskaya.

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