Air pressure, wind and fronts – Coriolis effect
GeographyWeather & ClimateAges 15–16
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Weather & Climate
A pressure map with a draggable high-pressure centre (H) and low-pressure centre (L), with isobars drawn automatically. Air parcels move from high to low pressure and are deflected by the Coriolis effect (to the right in the Northern Hemisphere, to the left in the Southern Hemisphere), forming an anticyclone around the high and a cyclone around the low; change the pressure difference, latitude, hemisphere and friction to see how wind speed and direction change. The panel below shows a cross-section of a cold front (cold air undercuts and lifts warm air, bringing thunderstorms) or a warm front (warm air glides up over cold air, bringing steady rain).
Lesson: Air pressure and wind; fronts; the Coriolis effect on wind direction
What it shows
Wind is air moving from high to low pressure, pushed by the pressure gradient force; closely spaced isobars mean a steep gradient and a strong wind. Because Earth rotates, the Coriolis effect deflects moving air to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, and the deflection grows from zero at the Equator to a maximum at the poles. Well above the ground, wind blows almost parallel to the isobars; near the surface, friction slows it so it crosses them towards low pressure. Fronts are boundaries between air masses where warm air is forced to rise, forming cloud and rain.
How to use
Drag the H and L centres closer together or further apart and watch the isobar spacing and the speed of the air parcels. Change the Pressure difference between the high and low centres, then switch the Hemisphere and compare the direction of rotation around each centre. Move the Latitude slider between 5° and 80° to see the deflection change, and turn Friction with the ground on and off. Finally, compare the Cold front and Warm front cross-sections.
Parameters you can change
- Pressure difference between the high and low centres 4–40 hPa
- Hemisphere Northern Hemisphere (deflects right), Southern Hemisphere (deflects left)
- Latitude (Coriolis effect increases with latitude) 5–80 °
- Friction with the ground (wind crosses the isobars)
- Show front cross-section
- Front type Cold front, Warm front
Questions to explore
- Why does air not flow straight from the high-pressure centre to the low-pressure centre?
- How does the direction of rotation around a low differ between the Northern and Southern Hemispheres?
- Why does a cold front bring short, heavy showers while a warm front brings long, steady rain?
