What Is the Atmosphere and How Is It Measured?
The atmosphere is the thin layer of gas around Earth, mostly nitrogen and oxygen, and nearly all weather happens in its lowest layer, the troposphere. Meteorologists describe it with a few basic measurements: pressure, the weight of the air above; temperature; humidity; and the dew point, which shows how much water vapor the air actually contains.
This is where it all starts. Before radar loops and supercells, you need to know what air is and how we measure it. Four short lessons: the layers, pressure, temperature and the dew point. Do not skip the dew point one. Future you, staring at a storm forecast, will be glad you didn't.
What You’ll Learn
- What air is made of and why water vapor matters most for weather
- The layers of the atmosphere and why storm anvils flatten at the tropopause
- What air pressure is, the units used and why it falls with height
- The four ways heat moves: conduction, convection, radiation and advection
- Why the daily high comes in the afternoon and how inversions form
- Why forecasters trust the dew point more than relative humidity
- How humidity drives the heat index
Lessons In This Unit
- 1.1What Air Is And How The Atmosphere Is LayeredFrom the ground up, the main layers are the troposphere, stratosphere, mesosphere and thermosphere, with the thin exosphere fading into space above. Scientists separate them by...Beginner · 7 min
- 1.2Air Pressure And How We Measure ItAir pressure is the weight of the column of air above you, about 14.7 pounds per square inch at sea level. Meteorologists measure it with barometers in millibars or inches of...Beginner · 7 min
- 1.3Temperature And How Heat MovesHeat moves through the atmosphere four ways. Conduction passes heat by direct contact, mostly right at the ground. Convection carries it upward in rising warm air. Radiation...Beginner · 7 min
- 1.4Humidity, Dew Point And SaturationRelative humidity is a percentage comparing how much water vapor is in the air with how much it takes to saturate it at the current temperature, so it rises and falls as...Beginner · 8 min
Questions People Ask
Where does weather happen in the atmosphere?
Almost entirely in the troposphere, the lowest layer, which holds about 80 percent of the atmosphere's mass and nearly all its water vapor.
What is normal air pressure?
Average sea-level pressure is 1013.25 mb, or 29.92 inches of mercury.
Is dew point or humidity better for judging comfort?
Dew point. It measures the actual moisture, while relative humidity changes with temperature.
Four lessons, and you will read every forecast differently. Promise. — Jen
