The Atmosphere The Atmosphere The atmosphere is the

The Atmosphere

The Atmosphere The atmosphere is the envelope of gases that surround our planet n It is a very thin layer compared to the radius of the Earth n

State of the Atmosphere n We discuss and study the atmosphere in terms of the following variables: Pressure n Temperature n Wind n Humidity n Cloud cover n Precipitation type and amount n Visibility (distance one can see horizontally) n

Weather vs. Climate • • Weather is the state of the atmosphere at a particular time and a particular place. Climate is the long-term state of the atmosphere at a particular location.

Atmospheric Composition Dry air (neglecting water vapor) is composed of the following gases: Nitrogen (N 2) = 78% Oxygen (O 2) = 21% Argon (Ar) = 1% Trace Gases Dust, bacteria, and other particulates

Atmospheric Composition n Trace Gases • Gases that are only found by examining a million or billion air molecules • Examples include: Carbon Dioxide (CO 2) = 340 ppmv n Neon (Ne) = 18 ppmv n Helium (He) = 5 ppmv n Methane (CH 4) = 2 ppmv n Hydrogen (H 2) = 0. 5 ppmv n

Composition of Air n n n There are many different types of gasses in the atmosphere They include nitrogen, oxygen, argon, carbon dioxide and other noble gasses The gas that is most abundant is nitrogen

Vertical Layers of the Atmosphere The Earth’s atmosphere has 4 distinct layers that are identified by the way temperature changes with height. These layers are: - Troposphere - Stratosphere - Mesosphere - Thermosphere

Vertical Layers of the Atmosphere (continued) n Layers of the atmosphere are determined based on how temperature changes

Troposphere n n This is the layer closest to the Earth’s surface Almost all the weather phenomenon we know of occurs in this layer. The depth of the troposphere varies by the season (deeper in summer) Temperature on average decreases with height.

Stratosphere n n n The next layer above the troposphere The boundary between the stratosphere and troposphere is called the tropopause. The ozone layer is found here Some clouds can form here near the poles Temperature increases with height Very little mixing occurs between the troposphere and stratosphere.

Mesosphere n n n The mesosphere is the next layer above the stratosphere. Clouds are rare in the mesosphere. Temperature decreases with height in the mesosphere

Thermosphere n n n The thermosphere rests above the mesosphere, and no clouds exist. Temperature increases with height in thermosphere. The highest temperatures for the atmosphere occur in thermosphere, but it doesn’t feel hot because the atmosphere is so thin up there.

Thermosphere (continued) n This is where most small meteorites burn up and is also the location in the atmosphere that the northern lights occur (aurora borealis)

Atmospheric Density n n n Density and pressure in the atmosphere decrease exponentially with height Approximately 75% of the total atmosphere is in the troposphere Approximately 99% of the atmosphere is the troposphere and stratosphere