Wet Bulb Temperature Calculator

Historical Background

The wet bulb temperature is crucial for determining atmospheric moisture content and predicting the cooling effect due to evaporation. The simplified formula used in this calculator is derived from a practical rule of thumb discussed in the literature, which approximates the relationship between dewpoint, relative humidity, and temperature. This method is based on empirical observations that in moist air (relative humidity greater than 50%), the temperature difference between dry and wet bulb decreases almost linearly.

Calculation Formula

The simplified calculation formula used in this calculator approximates the wet bulb temperature (\( T_{wb} \)) as:

\[ T{wb} \approx T{db} - \left( \frac{100 - RH}{5} \right) \]

Where:

• \( T_{db} \) is the dry bulb temperature in °C.
• \( RH \) is the relative humidity in %.

This rule of thumb is most effective for conditions where \( RH > 50\% \).

Example Calculation

Consider a dry bulb temperature of 30°C and relative humidity of 70%. Using the approximation:

\[ T_{wb} \approx 30 - \left( \frac{100 - 70}{5} \right) = 30 - 6 = 24 \, °C \]

Thus, the wet bulb temperature is approximately 24°C.

Importance and Usage Scenarios

1. Weather Forecasting: Wet bulb temperature helps meteorologists determine humidity levels, which are crucial for predicting weather conditions such as fog formation and potential precipitation.
2. Human Comfort Assessment: The wet bulb temperature gives a good indication of how comfortable a given environment is, especially in high temperatures. It is often used in heat stress calculations.
3. Agriculture and Irrigation: Farmers use the wet bulb temperature to determine the rate of evaporation, which influences irrigation requirements.

Common FAQs

1. What is the wet bulb temperature?

   • Wet bulb temperature is the lowest temperature that can be achieved by evaporative cooling. It reflects the cooling effect of evaporation and provides an indicator of the humidity in the air.

2. Why is the simplified calculation valid only for RH greater than 50%?

   • The relationship between dry and wet bulb temperatures becomes non-linear and less predictable for low humidity levels (below 50%), making this approximation unreliable.

3. Can wet bulb temperature be higher than the dry bulb temperature?

   • No, wet bulb temperature can never exceed the dry bulb temperature, as it accounts for the evaporative cooling effect, which always results in a lower or equal temperature.

This calculator offers a quick, approximate way to calculate the wet bulb temperature, useful for practical purposes where high precision is not necessary, such as educational use, general weather understanding, and preliminary agricultural planning.