1. What Is Water Vapor Pressure?

Water vapor pressure is the partial pressure of water vapor in any gas mixture in equilibrium with solid or liquid water. It represents the contribution of water vapor to the total atmospheric pressure and is a key parameter in meteorology and humidity calculations.

2. How Does The Calculator Work?

The calculator uses the water vapor pressure equation:

Where:

• \( e \) — Water vapor pressure (hPa)
• \( RH \) — Relative humidity (%)
• \( e_s \) — Saturation vapor pressure (hPa)

Explanation: The equation calculates the actual vapor pressure by multiplying the saturation vapor pressure by the relative humidity expressed as a decimal fraction.

3. Importance Of Water Vapor Pressure Calculation

Details: Accurate water vapor pressure calculation is essential for meteorological forecasting, HVAC system design, industrial processes, and understanding atmospheric thermodynamics and humidity effects.

4. Using The Calculator

Tips: Enter relative humidity as a percentage (0-100%) and saturation vapor pressure in hPa. The saturation vapor pressure depends on temperature and can be calculated using various formulas like the Magnus formula or obtained from standard tables.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between absolute and relative humidity?
A: Absolute humidity is the actual mass of water vapor in a volume of air, while relative humidity is the ratio of current vapor pressure to saturation vapor pressure at the same temperature.

Q2: How does temperature affect vapor pressure?
A: Saturation vapor pressure increases exponentially with temperature, meaning warm air can hold much more water vapor than cold air at the same relative humidity.

Q3: What are typical values for water vapor pressure?
A: In Earth's atmosphere, vapor pressure typically ranges from 0-40 hPa, with higher values in tropical regions and lower values in polar regions or at high altitudes.

Q4: How is saturation vapor pressure determined?
A: Saturation vapor pressure is typically calculated using temperature-dependent empirical formulas like the August-Roche-Magnus approximation or obtained from thermodynamic tables.

Q5: Why is vapor pressure important in weather forecasting?
A: Vapor pressure helps determine dew point, relative humidity, and is crucial for predicting fog, precipitation, and understanding heat index and apparent temperature.