1. What is Pressure Gradient Force (PGF)?

Definition: The pressure gradient force is the force that results when there is a difference in pressure across a surface, causing movement from high to low pressure.

Purpose: In meteorology and fluid dynamics, it's the primary force responsible for initiating wind and fluid motion.

2. How Does the PGF Work?

The calculator uses the formula:

Where:

• \( PGF \) — Pressure Gradient Force (m/s²)
• \( \nabla P \) — Pressure gradient (Pa/m)
• \( \rho \) — Density of the fluid (kg/m³)

Explanation: The negative sign indicates the force is directed from high to low pressure. Greater pressure differences over shorter distances create stronger forces.

3. Importance of Pressure Gradient Force

Details: PGF is fundamental in atmospheric sciences, explaining wind patterns, storm development, and ocean currents. It's one of the primary forces in the Navier-Stokes equations.

4. Using the Calculator

Tips: Enter the pressure gradient (change in pressure per meter) and fluid density (default 1.225 kg/m³ for air at sea level). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is the PGF negative?
A: The negative sign indicates the force acts from high to low pressure areas.

Q2: What's a typical pressure gradient in weather systems?
A: For large-scale weather, typically 1-5 Pa/km (0.001-0.005 Pa/m). Strong storms may have gradients up to 10 Pa/km.

Q3: How does density affect PGF?
A: Lower density fluids (like warm air) experience greater acceleration from the same pressure gradient.

Q4: What other forces act with PGF in the atmosphere?
A: Coriolis force, friction, and centrifugal force all interact with PGF to determine actual wind patterns.

Q5: How is pressure gradient measured?
A: Using pressure observations from weather stations or buoys, calculating the difference over distance.