《环境化学》课程PPT教学课件讲稿（英文版）Unit 1 Atmospheric structure

Atmospheric structure

Atmospheric Structure

The atmosphere The atmosphere is a thin blanket of gas that envelops the earth The gases that make up the atmosphere are held close to the earth by the pull of gravity With increasing distance from the earth's surface, the temperature, density, and composition of the atmosphere gradually change On the basis of air temperature, the atmosphere can be divided vertically into four major layers

The atmosphere • The atmosphere is a thin blanket of gas that envelops the earth. • The gases that make up the atmosphere are held close to the earth by the pull of gravity. • With increasing distance from the earth’s surface, the temperature, density, and composition of the atmosphere gradually change • On the basis of air temperature, the atmosphere can be divided vertically into four major layers

Atmospheric structure 300 200 Thermosphere Mesopause ionosphere Mesosphere Stratopause Ozone 40 Stratosphere Lay Tropopause 20 Troposphere -100 0 5 100 Temperature (oC)

Atmospheric structure

Troposphere The troposphere is the layer from the earths surface to the tropopause, which is at 10-15 km altitude depending on latitude and time of year( Mt Everest 8.85km) As altitude increases air temperature decreases at a rate of about 3.5 per 1000 ft. The tropopause has a temperature of about -57oC The lower part of the troposphere interacts directly with the surface of the earth-this part of the troposphere is generally called air. The atmosphere in this layer is heated from below by convection and radiation from the earth s surface Most of our weather occurs in the troposphere

Troposphere • The troposphere is the layer from the earth’s surface to the tropopause, which is at 10-15 km altitude depending on latitude and time of year. (Mt. Everest 8.85km) • As altitude increases, air temperature decreases at a rate of about 3.5o per 1000 ft. The tropopause has a temperature of about –57oC. • The lower part of the troposphere interacts directly with the surface of the earth–this part of the troposphere is generally called air. • The atmosphere in this layer is heated from below by convection and radiation from the earth’s surface. • Most of our weather occurs in the troposphere

Stratosphere The stratosphere is the layer above the troposphere and extends to about 50km The temperature rises with increasing altitude, reaching a maximum of about -1C at the stratopause The ozone layer is in the stratosphere. Ozone absorbs Uv, causing the rising temperature with altitude in this layer The temperature structure keeps the air calm in this layer. (That's why jet aircraft fly in the lower stratosphere

Stratosphere • The stratosphere is the layer above the troposphere and extends to about 50km. • The temperature rises with increasing altitude, reaching a maximum of about –1 oC at the stratopause. • The ozone layer is in the stratosphere. Ozone absorbs UV, causing the rising temperature with altitude in this layer. • The temperature structure keeps the air calm in this layer. (That’s why jet aircraft fly in the lower stratosphere!)

Mesosphere The mesosphere extends from the top of stratopause to 80 km In the mesosphere, the temperature decreases with altitude

Mesosphere • The mesosphere extends from the top of stratopause to ~80 km. • In the mesosphere, the temperature decreases with altitude

Thermosphere The layer of air above mesosphere is called thermosphere In the thermosphere temperature rises with altitude, caused by absorption of UV solar radiation by n2 and o2

Thermosphere • The layer of air above mesosphere is called thermosphere. • In the thermosphere, temperature rises with altitude, caused by absorption of UV solar radiation by N2 and O2

The lower atmosphere The troposphere and the stratosphere together are called the lower atmosphere The lower atmosphere account for 99. 9% of total atmospheric mass The lower atmosphere is the domain of main interest from an environmental perspective Ozone depletion(stratosphere) Air pollution(troposphere)

The lower atmosphere • The troposphere and the stratosphere together are called the lower atmosphere. • The lower atmosphere account for 99.9% of total atmospheric mass • The lower atmosphere is the domain of main interest from an environmental perspective. – Ozone depletion (stratosphere) – Air pollution (troposphere)

Ionosphere Ionosphere is a region where ions and electrons are most abundant This region is located at altitude above 60km therefore lie within the mesosphere and above

Ionosphere • Ionosphere is a region where ions and electrons are most abundant. • This region is located at altitude above 60km, therefore lie within the mesosphere and above

Ionosphere Ionosphere acts as a conducting layer Re flec tive Region in the upper atmosphere that would allow a transmitted electromagnetic Transmitter Receiver signal to be reflected back toward the earth

Ionosphere Ionosphere acts as a conducting layer in the upper atmosphere that would allow a transmitted electromagnetic signal to be reflected back toward the Earth