How to work with temperatures and humidity in mushing?

Continuation of the article Overheating and cooling of the dog sprinter. The biggest limit in dog pull training is the high air temperature. We have already written something about overheating in the article Overheating and cooling of a dog sprinter. Humidity combined with temperature and wind force during training I mentioned only marginally in the article. In the following lines, we will focus on these quantities in more depth. We will write why it is good to know the effect of humidity and wind force on the air temperature and try to understand the formula for calculating the feels like temperature.

Beware of high air temperatures

The first signal to leave the harness on the hanger and the dogs in the litter should be the air temperature. As we explained in the article on overheating, the dog cannot sweat and its cooling system therefore relies on other mechanisms, especially the low temperature of the surrounding air in combination with its flow. The main "coolers" in a dog are its ears, tongue and, last but not least, the entire surface of the body, which releases the accumulated heat by radiation. For your dog, the high temperature can be above 15 ºC. However, this value takes many forms and 15 ºC is not always the same. Why? It depends on other factors such as relative humidity, wind force and sunlight intensity.

Humidity

Humidity is still an easily measurable quantity. Each local weather station lists it in %. We will be interested in the relative humidity of the air, which is expressed by the amount of water vapor in the air. The basic characteristic of air humidity is the water vapor pressure, which expresses the water vapor pressure in a mixture with dry air. In layman's terms, the higher the humidity, the harder it is for the sweat to evaporate from the body surface or, in the case of a race dog, water from the fur (if you soak the dog). However, this does not mean that 100% humidity is ideal for training, because your dog will not dry so quickly. On the contrary, high humidity combined with high temperature is a deadly combination. This brings us to a combination of humidity and "feels like temperature", which we call the combination temperature, and it is no longer so easily measurable.

Wind Chill

This method is only used at temperatures below 10 ° C and wind speeds above 1.3 m / s. In addition to the measured temperature, it also takes into account the strength of the wind. The human body creates a thin layer of heated air around itself in an environment with a lower than body temperature. This layer can be disturbed, or "Blown away", so we feel more cold than would correspond to the measured temperature.

Feels like temperature

The temperature measured by a thermometer indicates a physical quantity - that is, information about the air temperature. However, everyone somehow subconsciously suspects that at 30 ° C in big city they will feel completely different than at 30 ° C in the rainforest. How we subjectively feel temperature is affected by many factors. It is for these reasons that the so-called "feels like temperature" is often mentioned, which can take into account, for example, wind speed, humidity or even the amount of sunlight. There is no single formula for calculating this data. The most commonly used formula is this:

AT = T + 0,33*e – 0,7*v – 4, where T is the air temperature (° C), v is the wind speed (m / s) and e is the water vapor pressure (hPa). The following then applies to: e = (RH / 100) * 6,105 * exp((17,27 * T) / (237,7 + T)), where RH is the relative humidity (in%), T is the temperature (° C) and exp is the exponential function. It is very important to realize that the feels like temperature depends mainly on the combination of wind force, humidity, ambient temperature and the intensity of sunlight. As a converter, I am adding several tables that clearly show the feels like temperature under certain conditions. Windless temperature in different humidity levels: Example: At a temperature of 10 ° C and a humidity of 50%, the sensory temperature is 8.5 ° C.

Feeling temperature under different wind forces at different humidity levels: Example: At a temperature of 10 ° C, a humidity of 50% and a wind speed of 9.7 m / s (35 km / h), the sensory temperature is 1.2 ° C.

Feeling temperature under different wind forces in average humidity in the Czech Republic (70%):

Practical use in mushing

The practical use for training may not be obvious at first glance. Feeling temperature is more valuable than just air temperature because it takes into account humidity and gusts of wind. If we can calculate the sensory temperature very accurately, it only depends on the coach's ability to draw conclusions from the values ​​obtained. It is logical that the limit temperature for canicross will be different than for scooter and bicycle. The IFSS (International Federation of Sleddog Sports) Rules of Procedure deal with this problem more precisely. Although we have calculated the correct temperature for the given locality under the current conditions, keep in mind that we still proceed from the general formula, which gives average numbers. It takes into account the average wind speed at a given location, temperature and relative humidity, which prevail directly at the measuring sensor. All these factors can change rapidly in different parts of the track. This brings us to the level of the microclimate for the given location and there can be several of them on the 6 km long track. The temperature here can oscillate by 5 to 10 ° C.

You can also use an unofficial formula that will tell you immediately whether it is good to start or not. Multiply the temperature by the humidity. Example 18 ° C at 85% humidity. If the product is higher than the number 1500 for canicross, it is recommended to shorten the track or not start at all. If the product is higher than 1360 for wheel classes, it is also canceled or shortened. However, it always depends on the plant director and the conditions on site. According to the racing rules, the temperature and humidity are measured 50 cm above the ground at the start point. However, as we wrote above, the conditions change along the track and if the start is in the forest by the stream and the rest of the track through the meadows, then the starting value is misleading.

Race what you train and train what you race

It seems like a trivial lesson, but it hides a simple relationship. If you average the product of temperature and humidity for the last month of training and get a value of 700, then it is clear that a race worth 1300 will be a nice mess for your dog. He is used to training at temperatures around 8-10 ° C at a humidity of 70% and suddenly he arrives at a race with a temperature of 16 ° C and a humidity of 81%. Although the race rules allow you to start, you can easily cook your dog, because the conditions to which the body is accustomed are suddenly almost twice as high. Therefore, it is good to guard these values, even if only for guidance.

Conclusion

Long clearings in the middle of the forest with almost zero gusts of wind in direct sunlight. A glowing hot road in the late afternoon. This is a murderous cocktail that should be avoided. Another common mistake is to go training after the summer rain. The relative humidity is then maximum and with zero wind gust and summer temperature it creates a murderous combination for training. We could continue the list, but that is not the subject of the article. As a bonus to the article, I enclose a table for calculating the sensory temperature, which I compiled in Excel, it can take into account the temperature, humidity and wind force.

Download temperature matrix HERE Sources: Portál ČHMÚ www.priroda.cz