1. What is Vapor Pressure?

Vapor pressure is the pressure exerted by water vapor in the atmosphere. It represents the partial pressure of water vapor in the air and is an important parameter in meteorology, HVAC, and various scientific applications.

2. How Does the Calculator Work?

The calculator uses the vapor pressure equation:

Where:

• \( e \) — Vapor pressure (hPa)
• \( RH \) — Relative humidity (%)
• \( e_s(T) \) — Saturation vapor pressure at temperature T (hPa)
• \( T \) — Temperature (°C)

Explanation: The saturation vapor pressure \( e_s(T) \) is calculated using the Tetens formula: \( e_s(T) = 6.112 \times \exp\left(\frac{17.67 \times T}{T + 243.5}\right) \)

3. Importance of Vapor Pressure Calculation

Details: Vapor pressure is crucial for understanding humidity levels, predicting weather patterns, designing HVAC systems, and studying evaporation processes. It helps determine the actual amount of moisture present in the air.

4. Using the Calculator

Tips: Enter relative humidity as a percentage (0-100%) and temperature in degrees Celsius. The calculator will compute the vapor pressure in hectopascals (hPa).

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between vapor pressure and relative humidity?
A: Vapor pressure measures the actual amount of water vapor in the air, while relative humidity expresses how close the air is to saturation at a given temperature.

Q2: Why use the Tetens formula for saturation vapor pressure?
A: The Tetens formula provides a good approximation of saturation vapor pressure over water for meteorological purposes and is widely used in weather forecasting.

Q3: What are typical vapor pressure values?
A: Vapor pressure typically ranges from 0 hPa in very dry conditions to about 40 hPa in very humid tropical conditions.

Q4: How does temperature affect vapor pressure?
A: Warmer air can hold more moisture, so saturation vapor pressure increases exponentially with temperature.

Q5: Can this calculator be used for frost point calculations?
A: This calculator uses the water saturation formula. For frost point calculations, different saturation formulas over ice would be needed.