ATMO 1

Atmosphere

The layer of gases around Earth. It shields us from the sun's harmful rays and solar wind, and its gas mixture lets life flourish. The sun's interaction with it drives weather.

Weather vs. Climate

Weather is the state of the atmosphere at a specific time and place. Climate is average weather over a long time. If weather is mood, climate is personality.

Meteorology

The study of the atmosphere and its phenomena.

Geostationary Satellite

A satellite that orbits Earth at the same rate Earth rotates, so it stays over the same spot.

Mid-Latitude Cyclone

A low pressure system that forms in the mid-latitudes. Low pressure systems produce warm and cold fronts.

Wind Direction

The direction the wind is coming FROM. Planes take off and land into the wind.

High vs. Low Pressure Circulation

Winds circulate clockwise around a high and counterclockwise around a low (Northern Hemisphere).

Wind Barbs

The line points toward where the wind is coming from. A short bar is 5 knots, a long bar is 10 knots, and a pennant (triangle) is 50 knots. The values add together.

Station Model Circle

How filled in the circle is shows how much of the sky is covered by clouds.

Dew Point

The temperature the air must cool to in order to become saturated. A higher dew point means more moisture in the atmosphere.

Early Atmosphere

Earth's first atmosphere was mostly hydrogen and helium. CO2 and H2O escaping from the cooling interior formed rain and oceans. The oceans absorbed CO2, and plants converted CO2 to oxygen.

Extent of the Atmosphere

There is no hard upper limit, because it just gets thinner and thinner. 99% of it is within about 20 miles of the surface.

Composition of the Atmosphere

78% nitrogen, 21% oxygen, and 0.9% argon.

Water Vapor and CO2 (Weather-Relevant Gases)

Water vapor, CO2, and other greenhouse gases are tiny percentages but matter most for weather. CO2 is about 0.042%. Water vapor varies from 0 to 4%.

Water in the Atmosphere

It exists in all three phases (vapor, liquid, ice), and it changes phase.

CO2 Sawtooth Pattern

CO2 rises and falls each year with the seasons. It drops when plants are growing and absorbing CO2, and spikes when plants die and decay. The overall trend is still upward.

Ozone (O3)

Good up high, where it absorbs UV in the stratosphere. Bad nearby, where it is a pollutant at ground level.

Air Pressure

Measured as the total mass of air above a point.

Standard Sea Level Pressure

1013.25 mb, or 29.92 inches of Hg.

Lapse Rate

The rate that temperature decreases with height

Temperature Inversion

When temperature increases with height, the opposite of the normal lapse rate.

Layers of the Atmosphere

Four layers, classified by how temperature changes with height: troposphere (decreases), stratosphere (increases), mesosphere (decreases), thermosphere (increases).

Troposphere

The lowest layer, where we live and where weather happens. Temperature decreases with height. The average lapse rate is about 3.5°F per 1000 feet.

Tropopause

The boundary between the troposphere and the stratosphere.

Stratosphere

Temperature increases with height. UV rays hit ozone, breaking it apart and releasing energy as heat.

Mesosphere

Temperature decreases with height.

Thermosphere

Temperature increases with height.

Sounding (Vertical Profile)

A vertical profile of the atmosphere, usually measured by a weather balloon. It shows the lapse rate.

Exosphere

The outermost layer, where air is extremely thin and gradually fades into space.