How Do We Measure Temperature?

Posted: October 2, 2017, 2:57 pm by mpriante

You’ve seen it before: on the evening weather report, in your home, on your phone, and even displayed on your local bank’s signage. Temperature is everywhere. It is one of the most crucial points in any forecast. It can determine whether you’re sweating or shivering, or if it’s wet or frozen outside. For the busy person on the go, the temperature can be the difference between a light jacket and a full-fledged parka during the winter. Temperature is very important to meteorologists because everyone depends upon it in one way or another.  Today, we are going to talk about how it is measured (properly), and how very beneficial good temperature readings are. 
Thermometers come in many different shapes and sizes, from the old-fashioned mercury tube varieties to the more modern digital sensors. Much of the temperature data meteorologists use in modern times are computed from digital sensors, but you will still see some old school thermometers in use. Stevenson Screens are a prime example of their usage today. 

Named after the man who developed it, this chicken coop-like box houses instruments that help to measure not only the temperature but also the relative humidity. The structure is designed in a way to shelter these thermometers from the elements and allows great ventilation, which means a more accurate representation of what conditions are like.
 

Stevenson Screen
 

So let’s say you don’t have one of these fancy temperature shelters and want to set up a thermometer outside for yourself. Here’s how to get the most accurate readings:

1. First, place your thermometer roughly 5 feet above the ground. Having it too close to the ground may pick up excess heat from the Earth, and having it too high up can keep it too cool.  

2.
You’ll also want to have your thermometer set up in the shade. Keeping it out of direct sunlight prevents solar radiation from heating up the instrument to a point that is higher than that of the actual ambient air temperature that you feel. 
 

3.     Having a good enough airflow will also aid in your temperature taking skills. Keeping the set up away from any obstructions like trees and buildings will prevent errors from occurring. This allows your reading to be the most representative of the actual temperature as possible.
 

4. Make sure the thermometer is placed over an earthy plot, like grass or dirt. Asphalt and concrete warm much more efficiently (and to a warmer temperature) than the Earth, leading to your equipment warming faster than the surrounding air and providing an “incorrect” reading.
 

5. Finally, just like how the Stevenson Screen keeps the thermometers sheltered from the elements, so too must your setup be covered. It can be as simple as creating a makeshift wooden box with adequate ventilation. 

 

If you follow the steps above, you will have an instrument that provides a reading that is much closer to being accurate than just leaving a thermometer in a window or on the outside of a house. Now that you are a temperature taking expert, you should have no trouble going out there and collecting some measurements!

Associate Meteorologist
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