1. What is Relative Humidity?

Relative humidity (RH) is the ratio of the amount of water vapor present in the air to the maximum amount that the air could hold at the same temperature, expressed as a percentage. It's a crucial parameter in meteorology, HVAC systems, and various industrial processes.

2. How Does the Calculator Work?

The calculator uses the relative humidity equation:

Where:

• \( RH \) — Relative Humidity (%)
• \( w \) — Specific Humidity (kg/kg)
• \( P \) — Total Atmospheric Pressure (Pa)
• \( e_s \) — Saturation Vapor Pressure (Pa)
• 0.622 — Ratio of molecular weights of water vapor to dry air

Explanation: This equation converts specific humidity (mass of water vapor per mass of moist air) to relative humidity by considering the saturation vapor pressure and total atmospheric pressure.

3. Importance of Relative Humidity Calculation

Details: Accurate relative humidity measurement is essential for weather forecasting, climate studies, industrial processes, agricultural applications, and maintaining comfortable indoor environments. It affects human comfort, material preservation, and various chemical and biological processes.

4. Using the Calculator

Tips: Enter specific humidity in kg/kg, total pressure in Pascals (Pa), and saturation vapor pressure in Pascals (Pa). All values must be positive numbers. For accurate results, ensure all measurements are taken at the same temperature and pressure conditions.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between specific humidity and relative humidity?
A: Specific humidity is the mass of water vapor per unit mass of moist air, while relative humidity is the ratio of actual vapor pressure to saturation vapor pressure at the same temperature, expressed as a percentage.

Q2: Why is 0.622 used in the equation?
A: 0.622 is the ratio of the molecular weight of water vapor (18.015 g/mol) to the molecular weight of dry air (28.965 g/mol), which is essential for converting between mass and pressure units.

Q3: How do I obtain saturation vapor pressure?
A: Saturation vapor pressure can be calculated using various empirical formulas (like Tetens equation or Magnus formula) that depend on temperature, or obtained from standard meteorological tables.

Q4: What are typical relative humidity values?
A: Relative humidity typically ranges from 0% (completely dry air) to 100% (saturated air). Comfortable indoor levels are usually between 30-60%.

Q5: Are there limitations to this calculation?
A: This calculation assumes ideal gas behavior and may have reduced accuracy at extreme temperatures or pressures. The accuracy also depends on the precision of the input measurements.