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


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.


This post is also available in: German French

Leave a Reply

Your email address will not be published. Required fields are marked *