Atmosphere Layers

Vertical Structure of the Earth’s Atmosphere Vertical temperature (T) profile: troposphere stratosphere mesosphere Thermosphere (contains both the ionosphere and magnetosphere) The atmosphere can be divided vertically into four layers based on temperature. Our atmosphere is unique to our planet in the solar system. One of NASA’s intentions is to locate similar sized planets with similar atmospheres.

Atmospheric Pressure Atmospheric pressure is force exerted by the weight of the air. The atmosphere rapidly thins as you travel away from Earth until there are too few gas molecules to detect.

How Pressure Changes with Altitude Atmospheric pressure decreases rapidly with height. Climbing to an altitude of only 5.5 km, where the pressure is 500 mb, would put you above one-half of the atmosphere’s molecules. Atmospheric pressure at sea level = 1013mb or 1 atm air density ( ρ pronounced “row”) air pressure (p) sea-level pressure (p s )

Layers of the Atmosphere Troposphere The troposphere is the bottom layer of the atmosphere where temperature decreases with an increase in altitude. The troposphere is the lowest layer of Earth's atmosphere. Most of the mass (about %) of the atmosphere is in the troposphere. Most types of clouds are found in the troposphere, and almost all weather occurs within this layer.weather The troposphere extends upward to about 10 km (6.2 miles or about 33,000 feet) above sea level. The boundary between the troposphere and the stratosphere is called the "tropopause" The limit of troposphere/tropopause varies with season and latitude. Temperature decreases with altitude – sea-level 15^C compared to the -60^C at the tropopause. Contains the majority of atmospheric water vapor Rapid decrease in water vapor with increasing height

Stratosphere Overview The stratosphere is the layer of the atmosphere where temperature remains constant to a height of about 20 kilometers. It then begins a gradual increase until the stratopause. Ozone (O3) is a primary absorber of solar UV. This creates a shield for the Earth from this destructive and dangerous emitted energy from our Sun.

Mesosphere and Thermosphere Overview Mesosphere: -50km-90km -Extends from the stratopause to the mesopause. -Temperature decreases with altitude (same as troposphere) -Coldest regions of the atmosphere -Combined troposphere and stratosphere contains 99.9% of the atmospheric mass, the remaining 0.1% exists in the Mesosphere. -Gases become thinner and thinner with increasing altitude. -Meteors burn up -Noctilucent clouds form (ice crystals = -85^C average) -Forms the mesopause (temp min) Thermosphere: The thermosphere is the region of the atmosphere immediately above the mesosphere and is characterized by increasing temperatures due to the absorption of very short-wave solar energy by oxygen. UV radiation is absorbed by oxygen molecules. UV radiation dissociates (breaks-up) molecules of CO2 and O2 and allows for energy loss to be a minimum, thus creating very hot molecules. Temperature increases with altitude to values in excess of 1,500 C. The temperature of the air is an expression of its kinetic energy, which is related to the speed at which its molecules move