Dew Point Calculator Formula

Dew Point Formula:

\[ Td = \frac{b \times \alpha}{a - \alpha}, \quad \alpha = \ln\left(\frac{e}{6.112}\right), \quad a=17.625, \quad b=243.04 \]

Dew Point Temperature (Td):

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1. What is the Dew Point?

The dew point is the temperature to which air must be cooled to become saturated with water vapor. When cooled further, water vapor will condense to form liquid water (dew).

2. How Does the Calculator Work?

The calculator uses the Magnus formula:

\[ Td = \frac{b \times \alpha}{a - \alpha}, \quad \alpha = \ln\left(\frac{e}{6.112}\right) \]

Where:

\( Td \) — Dew point temperature (°C)
\( e \) — Vapor pressure (hPa)
\( a \) — 17.625 (constant)
\( b \) — 243.04 (constant)

Explanation: The formula calculates the temperature at which water vapor in air condenses into liquid water at the current vapor pressure.

3. Importance of Dew Point Calculation

Details: Dew point is used in meteorology to predict frost, fog, and precipitation. It's also important in industrial processes where moisture control is critical.

4. Using the Calculator

Tips: Enter vapor pressure in hectopascals (hPa). The value must be greater than 0.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between dew point and humidity?
A: Humidity measures how much water vapor is in the air, while dew point indicates the temperature at which condensation occurs.

Q2: What is a comfortable dew point range?
A: Below 16°C (60°F) is comfortable, 16-18°C (60-65°F) is slightly uncomfortable, and above 18°C (65°F) becomes increasingly uncomfortable.

Q3: Can dew point be higher than air temperature?
A: No, this would require supersaturation which is unstable in the atmosphere and quickly leads to condensation.

Q4: Why use vapor pressure instead of relative humidity?
A: Vapor pressure is an absolute measure of water vapor content, while relative humidity depends on temperature, making it less precise for dew point calculations.

Q5: How accurate is this formula?
A: The Magnus formula is accurate to within about ±0.4°C for temperatures between -40°C and 50°C.