The atmosphere S6E4a: Demonstrate that land and water absorb and lose heat at different rates and explain the resulting effects on weather patterns. S6E4b: Relate unequal heating of land and water surfaces to form large global wind systems and weather events such as tornados and thunderstorms.

Warm Up: Monday February 10, 2014 What happens to the sun’s energy once it reaches earth?

Layers of the atmosphere Objectives: Identify the four main layers of the atmosphere. Describe the characteristics of each layer.

4 layers of the atmosphere The troposphere The stratosphere The mesosphere The thermosphere

The troposphere The lowest layer of the Earth’s atmosphere. This is where we live. The layer of the atmosphere in which Earth’s weather occurs. Air pressure decreases as you rise in the atmosphere. Although the shallowest layer, contains almost all of the mass of the atmosphere. As altitude increases, the temperature decreases.

The stratosphere The second layer of the atmosphere and contains the ozone layer. Extends from the top of the troposphere to about 50 km. The lower stratosphere is cold (about -60 degrees C), the upper is warmer. Why? Because the middle portion contains a layer of air where there is much more ozone than in the rest of the atmosphere. When the ozone absorbs energy from the sun, the energy is converted into heat, warming the air. The ozone layer protects Earth’s living things from dangerous ultraviolet radiation from the sun.

The mesosphere The 3rd layer of the atmosphere. Above the stratosphere Marked by a drop in temperature. Begins 50km above Earth’s surface and ends 80 km. In the outer mesosphere temperatures approach -90 degrees The layer of the atmosphere that protects Earth’s surface from being his by most meteoroids.

The thermosphere The outermost layer of Earth’s atmosphere The air is very thin. 80km above Earth’s surface No definite outer limit but blends with outer space Very hot! Up to 1800 degrees Sun strikes the thermosphere first, which causes it to be so hot. Divided into two parts: Ionosphere (lower layer) Exosphere (outer portion)

Energy from the sun Where does the heat in the atmosphere come from? Comes from the sun Travels to Earth as electromagnetic waves (a form of energy that can move through the vacuum of space) These are classified by wavelength Radiation: a direct transfer of energy by electromagnetic waves

Energy from the sun Most of the energy from the sun travels to Earth in the form of visible light and infrared radiation. A small amount arrives as ultraviolet radiation.

Includes all of the colors you see in the rainbow Visible light Includes all of the colors you see in the rainbow Red, orange, yellow, green, blue, indigo and violet Different colors = different wavelengths

Non-visible radiation Infrared radiation: one form of electromagnetic energy that has wavelengths that are longer than red light Not visible but can be felt as heat Ultraviolet radiation: Given off by the sun An invisible form of energy with wavelengths that are shorter than violet waves Can cause sunburns, skin cancer and eye damage

Energy in the atmosphere Some sunlight is absorbed or reflected by the atmosphere before it can reach the surface. The rest passes through the atmosphere to the surface. Some solar radiation is absorbed in the atmosphere Ozone layer absorbs most ultraviolet radiation Some sunlight is reflected Clouds reflect light back into space Scattering: dust particles and gases in the atmosphere reflect light in all directions – looks bluer than ordinary light (sky)

Energy at earth’s surface Some of sun’s energy reaches Earth’s surface and is reflected back into the atmosphere About half is absorbed by the land and water and changed to heat When Earth’s surface is heated, it radiates most of the energy back into the atmosphere as infrared radiation. This is absorbed by water vapor, carbon dioxide, methane and other gases in the air. This energy hats the gases in the air Gases form a “blanket” around Earth that holds heat in the atmosphere – this process is called the greenhouse effect

Heat transfer – thermal energy and temperature Thermal energy: the total energy of motion in the particles of a substance Air temperature is usually measured with a thermometer Thermometer: thin glass tube with a bulb on one end that contains a liquid Temperature is measured in degrees Two temperature scales: Celsius – freezing 0 degrees, boiling 100 degrees (scientists use this) Fahrenheit scale – freezing 32 degrees, boiling 212 degrees

How heat is transferred Heat: transfer of thermal energy from a hotter object to a cooler object Heat is transferred in three ways within the atmosphere: radiation, conduction, and convection

radiation Direct transfer of energy by electromagnetic waves Ex: warmth of the sun’s rays on your face – this energy was directly from the sun as radiation.

Conduction The direct transfer of heat from one substance to another substance that it is touching Ex: spoon in a pot of soup Ex: foot on sand on beach

convection The transfer of thermal energy by the movement of a fluid In liquids and gases, particles move easily from one place to another As they move, their energy goes along with them Caused by the difference of density

Heating the troposphere Radiation, conduction and convection work together to heat the troposphere During the daytime – sun’s radiation heats the surface Land becomes warmer that the air Air near surface heated by both radiation and conduction Only first few meters of troposphere by conduction Air close to ground warmer than a few meters up

Heating the troposphere Troposphere heated mostly by convection air near ground heats and spreads Cooler, denser air sinks toward surface, forcing the warmer air to rise As the warm air rises and cools, becomes more dense and sinks where it may be heated once again. This forms convection currents – upwards movement of warm air and the downward movement of cool air Convection currents move heat throughout the tropsphere