Meteorology The Study of the Atmosphere

Origin of the Atmosphere Several possible sources: Volcanic outgassing Incoming material from space

Composition of Early Atmosphere Gravity held the heavier gases in place Nitrogen, CO2 predominated

The Atmosphere Changes As earth cooled, water vapor condensed as precipitation. Earth has been recycling water since the outgassing began.

Lab 7: Structure of the Atmosphere Read intro material Plot Table 1 data, identify the various layers, answer questions

Structure of the Atmosphere The atmosphere consists of 4 layers: the troposphere, stratosphere, mesosphere, and thermosphere. The troposphere is the lowest layer of the atmosphere. This is the layer where we live and where weather happens. Temperature in this layer generally decreases with height.

Troposphere, Tropopause The boundary between the stratosphere and the troposphere is called the tropopause. The jet stream sits at this level and it marks the highest point that weather can occur. The height of the troposphere varies with location, being higher over warmer areas and lower over colder areas.

The Stratosphere Above the tropopause lies the stratosphere. In this layer the temperature increases with height. This is because the stratosphere houses the ozone layer. The ozone layer is warm because it absorbs ultraviolet (UV) rays from the sun. 

The Mesosphere and the Thermosphere  The mesosphere is the layer above the stratosphere. The temperature decreases with height here just like it does in the troposphere. This layer also contains ratios of nitrogen and oxygen similar to the troposphere, except the concentrations are 1000 times less and there is little water vapor there, so the air is too thin for weather to occur. The thermosphere is the uppermost layer of the atmosphere. In this layer the temperature increases with height because it is being directly heated by the sun.

ESRT on Atmospheric Structure

What is weather? Weather is the condition of the atmosphere at a particular location for a short period of time. The study of weather is called meteorology. Changes in weather are caused by variations in insolation, which distribute heat energy unevenly throughout the troposphere.

Weather Variables Temperature Air pressure Moisture (relative humidity and dew point) Precipitation (rain, snow, hail, sleet) Wind speed and direction, and cloud cover

Atmospheric Energy The sun is the main source on Earth for weather changes. Energy is described as the ability to do work. Earth processes, such as erosion, weathering, convection, and volcanism all involve energy. All matter at temperatures above absolute zero radiates energy (electromagnetic radiation)

Properties of Electromagnetic Energy Electromagnetic energy has the properties of transverse waves. The top of the wave is called the crest. The bottom of the wave is called the trough. The height of the wave is called its amplitude.

Wavelength The wavelength of a transverse wave is the distance between two successive crests or troughs. Wavelength identifies the type of EM energy that is radiated. The entire range of electromagnetic wavelengths is known as the electromagnetic spectrum.

The Speed of Light All EM energy travels through space at 3 x 108 m/s The number of wavelengths that pass through a given point in a second is the frequency. Frequency is expressed in cycles/s. Frequency is inversely proportional to wavelength

The Visible Spectrum Visible light makes up a tiny proportion of the EM spectrum. Our sun gives off a lot of visible light

Lab 8: The Electromagnetic Spectrum Objective You will observe the spectra of several light sources and draw what you see on the boxes on the following page.

Procedure Using your spectroscope glasses, look out the window at the bright sky. NEVER LOOK DIRECTLY AT THE SUN. In box number 1 on the following page, using colored pencils, draw a spectrogram of what you see. Look at a lightbulb and draw the spectra of what you see in box 2. After the teacher turns on the fluorescent lights, look at them and draw what you see in box 3. Look at the LED light on your cell phones; draw what you see in box 4. At stations around the room are four gas tubes filled with various elements. Draw a spectrogram for each element in boxes 4-8.

Emission Spectra of Air

Discussion Questions (Answer in complete sentences) List the colors of the visible portion of the electromagnetic spectrum in order (long wave to short wave) What is the difference between the the spectrum of the sun and that of the light bulb? What is the difference between the spectrum of the light bulb and the spectra of the gas tubes? There are many people who prefer incandescent light to fluorescent and LED light, even though these lights use much less energy. Using your spectrum, explain why. How is it possible to identify an element by looking at its spectrum?

Use the chart on page 14 of your reference tables to answer the following questions. How does the width of the visible spectrum differ from that of the ultraviolet portion of the spectrum? How does the wavelength of the infrared portion of the electromagnetic spectrum differ from that of the visible portion of the spectrum?

Matter and Electromagnetic Energy When EM energy comes in contact with a material, it can interact in several ways: It can be bent (refracted) as it passes through the material It can be scattered (refracted and reflected) in several different directions It can be absorbed by the material

Energy Transfer in the Atmosphere The movement of heat energy (infrared radiation) is particularly important in Earth Science. There are three ways energy is transferred: Convection Conduction Radiation

Convection Convection is the transfer of heat energy by the collision by movements of liquids and gases (fluids) When most fluids are heated, they expand; their density decreases, they rise Colder water, air is more dense, and sinks

Household Convection

Global Convection Processes

Solar Convection

Conduction Conduction is the transfer of heat energy by collisions of atoms or molecules with adjoining atoms or molecules. Conduction is most effective in solids, but can still occur in liquids and gases.

Lab 9 Heat Transfer by Conduction

Radiation Radiation is the transfer of electromagnetic energy through space in the form of invisible transverse waves. No medium is required for this transfer – convection and conduction require direct contact. The energy travels in straight lines at the speed of light. All objects are constantly radiating and absorbing EM energy.

Differences in Absorption and Radiation There are many different surface materials on land, unlike the ocean. Dark rocks and soils absorb more energy than light-colored ones. Surfaces that warm up faster also cool off faster – they are warmer in sunshine and cooler at night.

Lab 10: Absorption and Radiation of Energy

Measure Temperature Every Minute light on light off