Temperature Arithmetic

Temperatures reported in discussions about global change are usually mean temperatures (monthly or annual).  The mean temperature for any one day is calculated as:

T(mean) = [T(max) + T(min)] / 2

So what does a higher mean mean?  It could mean a higher daily maximum and the same minimum temperature, the same daily maximum and a higher daily minimum, or both could be higher!  So if you want to hide something, the mean is a pretty good choice.  Of course, during the course of the day, the mean temperature exists but for the shortest of times as it usually occurs at the inflection point of the daily sinusoidal curve of temperature.  So the mean happens sometime in the morning and sometime in the early evening. Weather stations recording daily minimum and daily maximum temperatures are known as the class B stations. 

T(range) = T(max) – T(min)

So daily temperature range could increase, decrease, or stay the same, depending on the particular arithmetic circumstance of T(mean).  In short, direct temperature readings are unambiguous.  Temperature means and temperature ranges are arithmetically derived concepts and thus ambiguous and not within everyone’s ken.  Mean annual is also a mind twister.  Seattle, Washington and Springfield, Illinois have about the about same mean annual temperature (53° F).  So what is one to do?  At least report the maximums and minimums.  That gives the inquiring mind at least a chance at comprehension! 

A max-min thermometer is a great help. Each day this thermometer provides a physical record of highest and lowest temperatures in the past 24 hours.  But there is a catch. You have to read the max-min thermometer at the same time of the day, every day. Who is so self-regimented as to invest time thermometer reading and stay in close physical presence to your weather station?

Dairy farmers are a good choice.  Those milkers need to be milked every day. Pastors need to be around their flock to advise on critical life issues. Pastors and milkers and their like usually take their measurements around 6 or 7 o’clock in the morning (early). If you can faithfully take readings for 50 years, you would earn the Jefferson Medal.

For those not arithmetically challenged, thinking about humidity and relative humidity is graduate study and the differences between temperature and heat are post graduate and perhaps rocket science.  CED will get to these issues in due time.


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