gen-define-wind-and-the-pressure-gradient-force-and-give-one-sho-b67d

Define wind and the pressure gradient force and give one short worked example.

# Wind and Pressure Gradient Force ## Definitions **Wind** is the horizontal movement of air from areas of high pressure to areas of low pressure. It is air in motion relative to the Earth's surface. **Pressure Gradient Force (PGF)** is the force that drives wind. It acts perpendicular to isobars (lines of equal pressure), directed from high to low pressure. The magnitude depends on how tightly packed the isobars are. The PGF per unit mass is calculated as: **PGF = -(1/ρ) × (ΔP/Δn)** where: - ρ = air density - ΔP = pressure difference - Δn = distance between pressure measurements ## Worked Example **Problem:** Two weather stations 100 km apart measure pressures of 1020 hPa and 1008 hPa. Air density is 1.2 kg/m³. Calculate the pressure gradient force per unit mass. **Solution:** Given: - ΔP = 1020 - 1008 = 12 hPa = 1200 Pa - Δn = 100 km = 100,000 m - ρ = 1.2 kg/m³ PGF = -(1/ρ) × (ΔP/Δn) PGF = -(1/1.2) × (1200/100,000) PGF = -0.01 m/s² The magnitude is **0.01 m/s²** or **10⁻² m/s²**, directed from the high pressure (1020 hPa) toward the low pressure (1008 hPa) station.