Apparent Temperature Calculator

Historical Background

The concept of apparent temperature was developed to better represent how humans perceive the temperature in various conditions, considering more than just the dry-bulb temperature (the actual measured temperature). Factors like humidity, wind speed, and radiation can significantly affect our comfort level. Therefore, the apparent temperature calculation was created to offer a more comprehensive understanding of temperature perception.

Formula

The formula to calculate the apparent temperature is:

\[ AT = T_a + 0.348 \cdot e - 0.7 \cdot ws + 0.7 \cdot \left( \frac{Q}{ws + 10} \right) - 4.25 \]

where:

• \( AT \): Apparent temperature in °C,
• \( T_a \): Dry bulb temperature in °C,
• \( e \): Humidity in hPa,
• \( ws \): Wind speed in m/s,
• \( Q \): Net radiation absorbed per unit area.

Example Calculation

Let's assume the following values:

• Dry bulb temperature: 28°C,
• Humidity: 20 hPa,
• Wind speed: 3 m/s,
• Net radiation absorbed: 100 W/m².

Using the formula:

\[ AT = 28 + 0.348 \cdot 20 - 0.7 \cdot 3 + 0.7 \cdot \left( \frac{100}{3 + 10} \right) - 4.25 \]

Simplifying:

\[ AT = 28 + 6.96 - 2.1 + 5.38 - 4.25 \approx 34.99 \text{ °C} \]

Importance and Usage Scenarios

The apparent temperature is crucial in understanding how environmental factors like humidity, wind, and radiation affect human perception of temperature. This understanding is vital in fields such as:

• Meteorology: Accurate forecasts for public health and safety.
• Occupational Health: Ensuring safe working conditions outdoors or in hot environments.
• Sports Science: Monitoring athlete safety during outdoor activities.

Common FAQs

1. Why does it feel hotter than what the thermometer says?

   • It could be due to high humidity or low wind speed, which impair the body's ability to cool down through perspiration.

2. What is reflected apparent temperature?

   • It’s the perceived temperature due to reflected photons from surfaces like buildings or pavements.

3. How does wind speed affect the apparent temperature?

   • Wind can either cool down or warm up a person depending on its speed and the surrounding temperature.