Coriolis Effect
The Coriolis Effect is the apparent deflection of moving objects — including air and water — caused by Earth's rotation. In the Northern Hemisphere, objects are deflected to the right of their direction of motion; in the Southern Hemisphere, they are deflected to the left. This effect is responsible for the rotation of large-scale weather systems such as cyclones and anticyclones, as well as global wind patterns like the trade winds and westerlies.
Key Formula
F_c = 2m(v × Ω)
LaTeX: F_c = 2m(\vec{v} \times \vec{\Omega})
| Symbol | Meaning | Unit |
|---|---|---|
| F_c | Coriolis Force | N |
| m | Mass of the moving object | kg |
| v | Velocity of the object | m/s |
| Ω | Angular velocity of Earth (7.27 × 10⁻⁵ rad/s) | rad/s |
Worked Example
Problem
Calculate the Coriolis acceleration experienced by a 10 m/s wind at a latitude where the Coriolis parameter f = 1 × 10⁻⁴ s⁻¹.
Solution
Step 1: Coriolis acceleration a_c = f × v, where f = 2Ω sin(φ). Step 2: a_c = 1 × 10⁻⁴ s⁻¹ × 10 m/s. Step 3: a_c = 1 × 10⁻³ m/s² = 0.001 m/s². This is small but cumulatively significant over hundreds of kilometres.
Answer
Coriolis acceleration = 0.001 m/s²
Coriolis Effect in Different Hemispheres
| Feature | Northern Hemisphere | Southern Hemisphere |
|---|---|---|
| Wind Deflection | To the right | To the left |
| Cyclone Rotation | Counterclockwise | Clockwise |
| Anticyclone Rotation | Clockwise | Counterclockwise |
| Trade Winds Direction | Northeast to southwest | Southeast to northwest |
| Effect Near Equator | Negligible (f ≈ 0) | Negligible (f ≈ 0) |
Interactive Tools
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Related Terms
Wind
Wind is the horizontal movement of air from regions of high atmospheric pressure to regions of low atmospheric pressure, caused by differential heating of the Earth's surface. The speed and direction of wind are determined by the pressure gradient force, the Coriolis effect (due to Earth's rotation), and friction with the surface. Wind is a major driver of weather patterns, ocean currents, and climate, and is harnessed as a renewable energy source through wind turbines.
Cyclone
A cyclone is a large-scale atmospheric system with low central pressure, around which winds spiral inward — counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere due to the Coriolis Effect. Tropical cyclones (known as hurricanes in the Atlantic and typhoons in the Pacific) are intense, warm-core systems that derive energy from warm ocean water, while extratropical cyclones are cold-core systems associated with mid-latitude weather fronts. Cyclones bring heavy rainfall, strong winds, and storm surges, and are among the most destructive natural weather phenomena.
Jet Stream
Jet streams are fast-flowing, narrow bands of wind in the upper atmosphere (typically 9–16 km altitude), reaching speeds of 160–480 km/h, found near the boundaries between cold polar air and warmer subtropical air. They flow generally west to east and meander in wavy paths, significantly influencing surface weather by steering storm systems, affecting flight times, and modulating temperature patterns. There are two main jet streams in each hemisphere: the polar jet and the subtropical jet.
Named after French mathematician and engineer Gaspard-Gustave de Coriolis (1792–1843), who first described the effect mathematically in his 1835 paper on equations of motion in a rotating frame of reference.