1. What is Actual Vapor Pressure?

Actual vapor pressure (e_a) represents the partial pressure of water vapor in the air. It's calculated from the saturation vapor pressure (e_s) and relative humidity (RH), providing a measure of the actual amount of water vapor present in the atmosphere.

2. How Does the Calculator Work?

The calculator uses the actual vapor pressure equation:

Where:

• \( e_s \) — Saturation vapor pressure (kPa)
• \( RH \) — Relative humidity (%)
• \( e_a \) — Actual vapor pressure (kPa)

Explanation: The equation calculates the actual amount of water vapor in the air by scaling the maximum possible vapor pressure (saturation) by the relative humidity percentage.

3. Importance of Actual Vapor Pressure Calculation

Details: Actual vapor pressure is crucial for meteorological studies, humidity control systems, agricultural planning, and understanding evaporative processes. It helps in predicting dew point, frost formation, and human comfort levels.

4. Using the Calculator

Tips: Enter saturation vapor pressure in kPa and relative humidity as a percentage (0-100%). Both values must be valid (e_s > 0, RH between 0-100).

5. Frequently Asked Questions (FAQ)

Q1: What is saturation vapor pressure?
A: Saturation vapor pressure is the maximum pressure of water vapor that can exist at a given temperature before condensation occurs.

Q2: How does temperature affect vapor pressure?
A: Saturation vapor pressure increases exponentially with temperature, meaning warmer air can hold more water vapor.

Q3: What are typical values for actual vapor pressure?
A: Actual vapor pressure typically ranges from 0.1 kPa in dry conditions to 4-5 kPa in very humid tropical environments.

Q4: How is this different from dew point?
A: Dew point is the temperature at which air becomes saturated, while actual vapor pressure measures the current amount of water vapor regardless of temperature.

Q5: Why is actual vapor pressure important in agriculture?
A: It helps determine evaporation rates, plant transpiration, and potential for fungal diseases that thrive in high humidity conditions.