How do we map surface temperatures?

isotherms.jpeg

Temperature is probably the weather variable that is most important to us.  We praise it when its nice, and complain when its not.  Most of us check it before we leave our homes each morning. 

We feel and describe temperature in terms of hot and cold, but temperature is actually a measure of the kinetic energy of molecules within a substance.  Fast moving molecules rub against each other generating heat through friction, while slow moving molecules are cold.

Isotherms

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Because it is so useful to us, we make maps showing us the temperature of different locations.  These maps like the one shown above look very similar to topographic maps because they have familiar looking curving lines.  

On topographic maps, contour lines are drawn to connect points with equal elevation.

On temperature maps, ISOTHERMS are drawn to connect points with equal temperature.

Rules for drawing isotherms:

  • Must be pretty - smooth flowing lines, no corners or sharp angles
  • No touching and no crossing
  • No dead ends

Isotherms Shift

Because temperature changes all the time, isotherms move around.  They shift towards the south in winter, and towards the North in the summer.

Because there is more land in the Northern Hemisphere, isotherms move more in the North than the South.