It’s a mistake we’ve all made: leaving home thinking it’s hotter outside than it really is and regretting leaving our winter coats behind.
As winter arrives and a strong cold front makes its way across the east of the country, Australians are more dependent on how fast it will be when they are out of the elements.
But if you often feel much colder than the weather forecast has warned, there is another measure of temperature that you should consider: temperature “seems”.
What is the “sensation” temperature?
As its name suggests, the “feeling” temperature is how we will feel when we venture outdoors.
The daily temperatures we see on our smartphones, in our cars and at the end of the nightly news take into account the temperature of the air, which is measured in isolation by a thermometer that is protected from wind, rain and the sun, also known as the Stevenson Screen.
It may not sound like much, but that’s how the BOM measures temperatures. (ABC Radio Perth: Emma Wynne)
While it’s a useful measure, it doesn’t take into account other factors that affect the way we experience temperature, such as humidity and wind (but we’ll talk about that later).
Basically, you can consider the “feeling” temperature to be an indication of how comfortable we feel when we are outside.
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How do you measure what “feels”?
It’s more than the outdoor atmosphere. The Bureau of Meteorology (BOM) has a mathematical equation for estimating how it really feels for an average person outside.
The actual recorded air temperature is taken into account, along with humidity and wind speed to determine the apparent temperature, which is what we know as the “sensation” temperature.
If you are interested in how it is, here is the equation.
AT = Ta + 0.33E – 0.70WS – 4.00
Don’t worry if math isn’t your forte. The BOM helps us with the numbers a bit, so all we have to do is decide if we should take a jacket before taking the dog for a walk.
Temperatures have plummeted in eastern Australia as a cold front swept across the country. (ABC News)
But there are some important assumptions that BOM makes to calculate how the temperature will feel when we are outside.
The BOM bases the “feeling” temperature on an adult who is dressed appropriately for the season, which means there are no T-shirts or shorts in the middle of a Victorian winter, for example, and they are outdoors. walking in the shade, not just direct.
This is because being in direct sunlight can raise the “feel” temperature by about 8 degrees Celsius, so the use of shade ensures that there is more consistency in the measurement.
The cooling of the wind can make us feel colder than expected. (AAP: Joe Castro)
Why does the temperature feel different?
Both humidity and wind affect the way we experience air temperature or what is forecast for the day.
For example, we will often feel colder when the wind is stronger. This is because the wind removes the thin layer of warm air we naturally have around our body to keep us comfortable.
When this goes away, our skin is more exposed and this makes us feel colder as a result.
But when the humidity is higher, it becomes harder for our sweat to evaporate, which would otherwise keep us cooler.
Given the wind and humidity, we get a more complete picture of the “feeling” of temperature, an important indicator as we prepare to shake for the next few months.
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