Geo D Unit 6 Lecture

Chapter 11 pages 271-282, all of Chapter 12, and Chapter 14 pages

559-363 and pages 370-377

CHAPTER 11PAGES 271-282

Key Atmospheric Gases

• The atmosphere is made up of many gases• 99% nitrogen and oxygen• Water vapor and carbon dioxide determine

temperature• Particulates are solids floating around in the

air that water vapor can condense on

Ozone

3 oxygen molecules bonded together• Located in the stratosphere• Absorbs UV rays and protect us from the sun

Layers of the Atmosphere

• Troposphere- closest to Earth, where most of the weather occurs, gets colder as your go higher

• Stratosphere- contains ozone, gets warmer as you go higher

• Mesosphere- very few molecules, coldest layer, gets colder as you go higher

• Thermosphere- hottest layer, gets hotter as you go higher

• Beyond the thermosphere is the exosphere which leads us into space

Solar Fundamentals

• Radiation:• The sun radiates onto Earth• 50% absorbed by the surface• 15% absorbed by atmosphere• 25% reflected from clouds back into space• 4% reflected by surface back into space• 6% reflected by atmosphere back into space

• Conduction:• Transfer of heat to

solids• Done by contact

• Convection:• Transfer of heat to

liquids and gases• Creates convection cells

in the atmosphere

Temperature verses Heat

• Temperature• Measure of the average

kinetic energy of molecules

• Heat• Transfer of energy

because of a difference in temperature

• Moves from high to low

Measuring Temperature

• In the United States we use Fahrenheit• For science class we will use Celsius or Kelvin• To convert from Celsius to Kelvin, simply add

273• 0 C = 273 K (freezing point of water)• 100 C = 373 K (boiling point of water)

Dew Point

• Dew point is the temperature when air reaches saturation

• Once dew point is reached, condensation happens (water vapor forms into water drops)

Vertical Temperature Changes

• In the troposphere, temperature decreases as elevation increases

• Cooling of 10 C for every 1000m increase• This is the dry adiabatic lapse rate• The height at which condensation occurs is

called the lifted condensation level (LCL)• Above the LCL, air cools more slowly

Air Pressure and Density

• The density of air is proportional to the number of particles present

• The density of air decreases as you move from the crust out into the atmosphere

Pressure Temperature Density Relationship

• Temperature is directly proportional to pressure

• Temperature decreases=pressure decreases• Ex: Moving higher up Mt. Everest• Pressure and density also directly proportional• Pressure decreases=density decreases

Temperature Inversions

• An exception to the rule that pressure and temperature decrease with height in the troposphere is an inversion

• Commonly happens when cities are in a basin and pollution becomes trapped there

Wind

• Caused by unequal heating of the earth’s surface

• Cool air sinks, warm air rises and allow for areas with differences in air pressure

• Wind speeds increase with altitude because there is less friction with objects and the earth

CHAPTER 12

Meteorology

• Meteorology is the study of atmospheric phenomena

• Hydrometeors are the items that contain water like clouds, rain, fog, etc

• Lithometeors are condensation nuclei like smoke and dust

• Electrometeors are the items that are a visible or audible manifestation of electricity like thunder and lightning

Weather verses Climate

• Weather• Current state of the

atmosphere• Short term

• Climate• Long term variations in

weather for a particular area

• The continual motion of air and water reallocates heat energy among Earth’s surface, oceans, and atmosphere and helps keep balance

Air Masses

• Air masses are large bodies of air over a certain area

• Those that form over land are drier than those over water

• Warm and dry = cT continental tropical• Warm and humid= mT maritime tropical• Cold and dry =cP continental polar• Cold and humid=mP maritime polar• Arctic A• All 5 air masses can be found in N America• Modification happens when they move away

from their source regions

Weather Systems

• The Coriolis Effect is the deflection of air to the right in the N Hemisphere and to the left in Southern

• Caused by the rotation of the earth

Global Wind Systems

• At the equator are the doldrums where ships would become stranded due to weak winds

• Trade winds occur above and below the equator

• Moves to the west• Also known as the Hadley cell

• Between the trades and the westerlies is a calm belt with weak winds called the horse latitudes

• Boats become stranded here• The prevailing westerlies blow to the east• The polar easterlies blow to the west

Jet Streams

• Jet streams are narrow bands of fast, high altitude winds

• Move up to 185 km/h• Two main jet streams:• 1. polar jet stream• 2. subtropical jet stream

Fronts

• A front is a narrow region separating two air masses of different densities

• Their interaction brings dramatic changes in the weather

• 4 types of fronts:• 1. cold front• 2. warm front• 3. stationary front• 4. occluded front

Cold Front

• Cold, dense air displaces warm air• Forces the air up along a steep front• Clouds, showers, sometimes thunderstorms• Drawn as a solid blue line with solid blue

triangles

Warm Front

• Advancing warm air displaces cold air• Develops a gradual frontal slope• Extensive cloudiness and precipitation• Drawn as a solid red line with solid red

semicircles

Stationary Front

• Small temperature and pressure difference between two air masses

• The boundary between them stalls• Mild weather patterns• Drawn as a combo of warm and cold front

symbols

Occluded Front

• Cold air moves so fast that it wedges warm air upward

• That cold air collides with an advancing cold front

• Precipitation is common• Drawn as alternating purple triangles and

semi circles

Pressure Systems

• High Pressure• Air moves outward in a

clockwise direction in N Hemisphere

• Fair weather

• Low Pressure• Moves inward in a

counter-clockwise direction in N Hemisphere

• Clouds and precipitation

Gathering Weather Data

• Thermometers measure temperature• Barometers measure air pressure• Anemometers measure wind speed• Hygrometer measures humidity• Ceilometer measures the height of the clouds

• Radiosonde measures temperature, air pressure, and humidity

• Sends radio signals back to the ground station from heights of 30,000m

Doppler Radar

• The Doppler effect is the change in frequency based on movement towards or away from the observer

• Doppler radar plots the speed that raindrops moved toward or away due to wind

Weather Satellites

• Weather satellites use both visible light and other forms of radiation to observe the atmosphere

• Infrared satellites detect changes in thermal energy

• Allow scientists to determine the temperature of a cloud to determine its type and height

Weather Analysis

• A station model is a record of weather data for a particular site at a particular time

• Isopleths are lines that connect points of equal values

• Temperature= isotherms• Pressure= isobars, closer together are

stronger winds

Forecasts

• Short term• Digital forecasts• Done by high speed

computers• Uses numerical data• Analog forecasts• Use past events

• Long term• Less accurate• Less detailed• Vague• Used more for seasonal

forecasts

CHAPTER 14PAGES 359-363 AND 370-377

Climate

• Climate describes the long term weather patterns of an area

• Variations in temperature, precipitation, wind, etc

• Data is such as daily high and low temps, rainfall, wind speed and direction, humidity, and air pressure is collected

• Averaged on a monthly or annual basis for 30 years

• This determines the normals (standard value)

Causes of Climate

• 1. latitude• The closer to the equator, the more direct the

sun’s rays hit and therefore receives more solar radiation

• 2. topography• Closeness to lakes and oceans• Warmer in winter and cooler in summer than

inland areas• Mountain climates cooler than sea level• Windward side of mountains are wet and

cool, leeward side is dry and warm

• 3. air masses• Warm and dry = cT continental tropical• Warm and humid= mT maritime tropical• Cold and dry =cP continental polar• Cold and humid=mP maritime polar• Arctic A

Short term climate changes

• Seasons are short term periods of climate change caused by variations in daylight, temperature, and weather patterns

El Nino

• El Niño is a warm ocean current that develops off the western coast of S America

• When the high pressure system and its trade winds weaken, changes in weather occur

• Causes stormy weather to normally dry places and drought conditions to normally wet

Natural Changes to Climate

• 1. solar activity• The sun’s sunspot cycles last about 11 years• A period of low sunspot activity is called a

Maunder Minimum, causes colder temperatures

• 2. Earth’s orbit• Earth’s orbit becomes more elliptical then

more circular and so on back and forth• When the orbit elongates, the earth is closer

to the sun, and temperatures become warmer

• 3. Earth’s tilt• Angle varies from 22.2 degrees to 24.5 every

41,000 years• Differences in angle could cause seasons to

become more severe

• 4. Earth’s wobble• By the year 14,000 Earth’s axis will point

toward the star Vega instead of Polaris• This will cause more extreme seasons

• 5. volcanic activity• When volcanoes erupt, they send out

immense quantities of dust into the atmosphere which blocks incoming solar radiation

The Human Factor

• The greenhouse effect allows for life to survive on earth, because a small portion of radiation is not allowed to reflect back into space

• This effect is impacted by the amount of greenhouse gases in the atmosphere

• These include carbon dioxide, methane, and water vapor

Global Warming

• Temperatures have increased over the past 200 years

• This warming is causes a melting of the polar ice caps

• This would then causes a rise in sea level• Scientists are not all in agreement about what is

causing global warming• Most blame our carbon dioxide output due to

burning fossil fuels