What is Weather?

Solar energy enters the atmosphere and is absorbed by land and surface water, which then emit infrared thermal radiation that warms the air. This heat either escapes into space or is trapped by atmospheric gases through the greenhouse effect. The resulting temperature differences drive convection circulation, where warm air rises and cool air falls, creating the pressure and temperature changes that produce daily weather variations across different locations.

Convection circulation is the process where warm, less dense air near Earth's surface rises into the upper atmosphere, which has lower pressure. As air rises and moves away from the heat source, it cools, becomes denser, and falls again. This continuous vertical movement of air masses creates local atmospheric changes in pressure, temperature, and rainfall that directly influence daily weather conditions.

Weather varies by location because the interactions between the sun, atmosphere, ocean, and land differ geographically. Solar radiation absorption and thermal radiation emission depend on local surface characteristics, while convection circulation patterns and atmospheric pressure systems are influenced by Earth's tilt and rotation. These combined factors create distinct weather conditions at different latitudes and elevations.

Meteorologists measure weather using temperature, atmospheric pressure, wind, humidity, precipitation, and cloudiness. Atmospheric pressure reflects the weight of the atmosphere above and indicates weather trends; high pressure typically brings cooler temperatures and clear skies, while low pressure associates with warmer weather and storms. These measurements allow meteorologists to predict short-term weather changes.

The greenhouse effect occurs when specific atmospheric gases trap thermal radiation emitted from Earth's surface, preventing heat from escaping into space. This retained heat warms the air and influences atmospheric temperature and convection patterns. Research indicates that anthropogenic climate change has intensified this effect, leading to increased frequency and intensity of extreme weather events and temperature extremes.

Extreme weather events include heat waves, cold waves, hurricanes, tornadoes, droughts, and floods. These events are typically sudden and harder to predict than daily weather. Meteorologists describe extreme events relative to historical weather patterns for specific locations. Climate models suggest that with ongoing climate change, Earth will experience more frequent and intense extreme weather, particularly persistent summer extremes in northern latitudes.

Atmospheric pressure reflects the weight of the atmosphere above a location. Observing pressure drops or rises allows meteorologists to make short-term weather predictions; falling pressure often signals approaching storms and warmer conditions, while rising pressure typically indicates clearing skies and cooler temperatures. These pressure trends provide early indicators of whether to expect rain or sunny weather.