How is Barometric Pressure Calculated

Barometric Pressure Formula (ISA):

\[ P = P_0 \times \left(1 - \frac{0.0065 \times h}{T_0}\right)^{\frac{g \times M}{R \times 0.0065}} \]

Barometric Pressure (P):

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1. What is Barometric Pressure Calculation?

Definition: This calculator estimates atmospheric pressure at a given altitude using the International Standard Atmosphere (ISA) model.

Purpose: It helps meteorologists, aviators, and scientists understand how pressure changes with altitude.

2. How Does the Calculator Work?

The calculator uses the ISA formula:

\[ P = P_0 \times \left(1 - \frac{0.0065 \times h}{T_0}\right)^{\frac{g \times M}{R \times 0.0065}} \]

Where:

\( P \) — Pressure at altitude (Pa)
\( P_0 \) — Sea level pressure (101325 Pa standard)
\( h \) — Altitude above sea level (meters)
\( T_0 \) — Sea level temperature (288.15 K standard)
\( g \) — Gravitational acceleration (9.81 m/s²)
\( M \) — Molar mass of air (0.02896 kg/mol)
\( R \) — Universal gas constant (8.314 J/mol·K)

Explanation: The formula models how pressure decreases exponentially with altitude in Earth's atmosphere.

3. Importance of Barometric Pressure

Details: Atmospheric pressure affects weather patterns, aircraft performance, and human physiology at different altitudes.

4. Using the Calculator

Tips: Enter altitude in meters, sea level pressure (default 101325 Pa), and sea level temperature (default 288.15 K). Temperature must be > 0 K.

5. Frequently Asked Questions (FAQ)

Q1: What is standard sea level pressure?
A: The standard atmospheric pressure at sea level is 101325 Pa (1013.25 hPa or 29.92 inHg).

Q2: Why does pressure decrease with altitude?
A: Pressure decreases because there's less atmospheric mass above higher elevations exerting downward force.

Q3: How accurate is this formula?
A: It's accurate for the standard atmosphere model but doesn't account for weather variations or local conditions.

Q4: What's the temperature lapse rate?
A: The standard lapse rate is 0.0065 K/m (6.5°C per km) in the troposphere.

Q5: Can I use this for very high altitudes?
A: This formula works best below 11 km (tropopause). Different models exist for higher altitudes.