What is and how is the wind chill calculated?

We have all heard talk either by meteorologists, mobile applications that tell us the weather or simply by general culture, that "it is such a temperature with such a thermal sensation." That thermal sensation it may or may not differ with the actual temperature we are at.

Do we really know what that wind chill is and how do meteorologists calculate it?

On a winter or summer day, we do not feel the same heat or cold if it is windy, there is more humidity or it is raining. Maybe we are on a winter day with 9 degrees of temperature but no wind, all calm and sunny and it is not the same as the same day with the same temperature but raining or with a north wind. It is that difference that we call thermal sensation. Is the cold or the heat that we perceive regardless of the actual temperature to which the environment is.

That difference in temperatures that exists between the sensation of the skin, the environment that surrounds us and the speed of the wind are what determine the amount of heat we lose from our body and is what makes us feel colder or hotter. In winter we know that the combination of cold and wind in the most exposed areas of our body is what determines the amount of heat we lose. That is why it is important to wear warm clothes to reduce the surface exposed to these changes in temperature and loss of body heat. Usually, The parts of the body that are most exposed to this thermal sensation are the hands, the face and sometimes the feet.

This thermal sensation arouses interest and curiosity in citizens, since sometimes and with relative frequency, we find ourselves in winter days in which we look at the thermometer and observe a not too cold temperature. However, we are cold. This is because if there is high humidity or cold windWe must wrap ourselves well because the ideal conditions will be given for our skin to lose our body heat.

So, as a summary we can define the thermal sensation as a temperature based on an index of body heat loss caused by combining temperature, wind and, to a lesser extent, humidity.

How is the wind chill calculated?

We know that the sensation of cold or heat can vary depending on the weather conditions of wind, humidity, etc. But how is the wind chill calculated?

There are tables that calculate the thermal sensation based on wind speed and temperature. Obviously if we coin the term wind chill as something subjective, these tables would not be of much use. That is, each person has their own perception and endurance in the face of cold and heat. Sometimes, there are people who can be in short sleeves with 10 ° C and others who at the same temperature need a lot of shelter on top. This does not mean that the ambient temperature may be 10 ° C, but the thermal sensation, due to wind or humidity conditions, is 7 ° C. That is, although the real temperature is 10 ° C, we we perceive it as if it were 7 ° C.

For example, according to these tables, at a temperature of 0 ° C and with a calm wind, we will probably not feel too cold if we are warmly dressed. However, with the same temperature but with a wind of about 40 km / h, the thermal sensation that we will have will be -15 ° C and it will be much colder. As a curiosity, if we stay at 0 ° C and winds of more than 65 km / h blow it can cause us health problems.

The calculation of the thermal sensation is not easy, because we look at the tables and that's it, but how were these values ​​calculated? Well, in the late 1930s, the explorer Paul Simple established an approach to the first mathematical formula for the calculation of the thermal sensation since he saw that in the polar zones, if the low temperatures were combined with the strong winds, the freezing became more imminent and therefore situations of greater danger were created .

This formula has been improved over the years until reaching its limit in 2001 through a consensus between Canadian and United States scientists. The definitive formula for calculating the thermal sensation is:

Tst = 13.112 + 0.6215 Ta -11.37 V0.16 + 0.3965 Ta V0.16

If we add values ​​to our formula we will be able to predict the temperature we will feel when going out, in this way we will know how to dress better to stay as cold as possible and avoid colds.