gen-define-high-and-low-pressure-systems-and-give-one-short-work-4c68

Define high- and low-pressure systems and give one short worked example.

# High- and Low-Pressure Systems ## Definitions **High-Pressure System (Anticyclone)** - Region where atmospheric pressure is higher than surrounding areas - Air descends, warms, and diverges at the surface - Generally brings clear, calm weather - Rotation: clockwise in Northern Hemisphere, counterclockwise in Southern Hemisphere **Low-Pressure System (Cyclone)** - Region where atmospheric pressure is lower than surrounding areas - Air converges at surface and rises, cools - Generally brings clouds, precipitation, and storms - Rotation: counterclockwise in Northern Hemisphere, clockwise in Southern Hemisphere ## Worked Example **Scenario:** A weather station measures atmospheric pressure of 1020 hPa while surrounding areas average 1013 hPa (standard sea-level pressure). **Analysis:** - Pressure difference = 1020 - 1013 = **+7 hPa** - This is a **high-pressure system** (pressure above surroundings) **Expected weather:** - Air sinks and warms → evaporates clouds - Result: **Clear skies, light winds, dry conditions** - If in Northern Hemisphere: winds blow **clockwise** outward from center **Contrast:** If pressure were 1006 hPa (7 hPa *below* average), it would be a low-pressure system with rising air, likely clouds, and possible rain.