The study of the entire atmosphere including its weather.

The atmosphere

  • air is a mixture of many gases in earths lower atmosphere
  • nitrogen and oxygen together form about 99% of dry air by volume
  • The remaining 1% is mainly argon and carbon dioxide

Structure of the atmosphere

Troposphere- is the lowest layer of the atmosphere (0-12KM) in which all of earths weather occurs

  • Gradually decreases in temp with an increase in altitude
  • contains all water vapor
  • The jet stream is located between (6-12KM)

tropopause- the top of the troposphere where the decrease in temp. stops

Stratosphere- reaches from the tropopause to about 50KM above the earth

  • Steady winds and few weather changes (planes fly here)
  • steady increase in temp with the increase of altitude which is caused by absorption from the ozone

Ozone- untraviolet rays make oxygen 03. The ozone layer absorbes suns UV rays and protectes us from burning.

Stratopause- the top of the stratosphere where the temp. stops rising

Mesosphere- temp drops again

Thermosphere- Temperature rises again about 500 Km from earth


What is the weather like outside?

Weather- is the state of the atmosphere at a given tie and place

To try to predict weather you n

eed to observe the clouds, wind, temp,humidity, and pressure and precipitation over a period of time

Heating of the atmosphere- energy from the sun results in changes in the weather. heat moves through the atmosphere in three ways

  • Conduction- An object receives heat when it comes in contact with a hotter object (Ex. a pan on a hot stove)
  • radiation- Hot bodies radiate energy in short waves (sun); Cold bodies radiate energy in long waves (earth)
  • Convection- most effective; the rising of hot air and sinking of cold air results in a steady flow. convection is very important in moving heat through the atmosphere


Solar energy- that reaches the earth; we receive one two billions of the sun


Green house effect - Short ultra violet waves from the sun are able to reach the earths surface. then longer infrared waves re-radiated by the earths surface are trapped by green house gasses (CFC's and CO2) Normal lapse rate- the rate of cooling with altitude (1 degree c every 160 meters) Temp inversion- when the air is especially still cooler air, because of its greater density settles close to the ground and the warmer air forms a blanket above it. In a temp inversion pollutants in the

air such as smoke and soot are also trapped close to the ground


Specific heat - The amount of heat required to raise the temp of something 1

degree C

water has a very high specific heat compared to soil
Absorption -
to take in energy and heat up
to bounce back energy
to absorb short wave energy and give off long wave energy

Good absorbers poor Absorbers

Heating of land and water

Which heats up faster ??

Water warms much more slowly than land

  • In water the sun's rays go to a depth of many meters. on land only the top few centimeters of soil is heated by the sun

  • water can spread heat easily because it is a fluid

  • some solar energy is used in the process of evaporation thus less solar energy

  • water cools more slowly than land because its heat is spread through a greater depth


Temp- is a measure of the energy of molecules the more energy the molecules in air have the hotter it feels

  • Temp is measured in degrees (celsius,fahrenheit,kelvin)
  • Thermometers are the instrument used to measure temperature
  • the alcohol expands when heated
  • Thermographs are self recording thermometers

Isotherms-are lines drawn on maps connecting places with the same temperature

evaporation-the change from liquid from liquid water to water vapor

humidity- the capacity of air for holding water vapor

  • as air temp increases so does the amount of water vapor it can hold

  • specific humidity- the amount of water vapor

  • relitive humidity- compares the acully amount of watery vapor in the air with the max amount of water vapor the air can hold at that temp

psychrometer- is the instrument used to determine relative humidity

condensation- the change from water vapor to a liquid this occurs when the temperature drops low enough that the capiticy for water vapor in the air drops below the specific humidity.


dew-water vapor which condenses on surfaces such as grass in the form of a liquid

dew point- temp at which saturated water occurs

air may be cooled below its dew point in many ways

  • contacting a colder surface
  • radiating heat
  • mixing with colder air
  • expanding when raises

water vapor needs to condense on something!!

condensation nuclei- tiny particles such as salt, sulfate, or nitrate particles on which water vapor condenses

  • when cooling occurs by contact with a colder surface the water vapor condenses directly on that surface >0 deg c =dew


surface layers of air a f

ew hundred meters thick which are cooled below the dew point. as water vapor condenses tiny droplets stay suspended in the air by the lightest air movement

Radiation fogs- at night the ground loses heat rapidaly light winds mix the cold bottom air with the air a short distance from the surface when the whole layer of air is cooled below the dew point a fog forms (common in humid valleys and near rivers and lakes)

advection fogs- results when warm moist air blows over cool surfaces (ex coastal California)

clouds- clouds form when air above the surface cools below the dew point

Precipitation- is the falling of any form of water from the air to the earths surface

  • occurs when clouds droplets grow into drops heavy enough to fall to earth

types of precipitation:

  • Raindrops- form from tiny droplets and then grow by bumping into and combining with other droplets

  • sleet- forms when raindrops fall through the freezing air and fall to the ground as pellets of ice

  • hailstones- begin as a frozen raindrop and grows by collecting smaller ice particles or liquid or cloud droplets

  • acid rain- forms when water condenses on sulfate and nitrate

Air pressure- the weight of the atmosphere per unit area

Differences in air pre

ssure cause the earths wind and weather changes


BAROMETER- is an instrument used to measure air pressure


Aneroid barometer- Measures pressure with a thin metal can

Mercury barometer - uses mercury to measure the pressure but not used as often

Millibar- is a metric unit of pressure

standard sea level pressure is 1013.2MB

Isobar- are lines that join points having the same air pressure at a given time

*each line is worth 4 MB

High pressure area- the area of the largest pressure the pressure in a high is greater than the surrounding air


Low pressure area- this area has lower pressure than the surrounding area

Pressure gradient- the rate of change for air pressure between two points

Rising barometer- greater pressure usually means cooler drier weather (sinking air)

Falling barometer- less pressure because the air is warm and moist and rises this can be a sigh of precipitation

WIND-the horizontal movement of air from areas of high pressure to areas of low pressure

*The closer the spacing between isobars the stronger the winds.

*winds blow across isobars from high to low air pressure

Global wind belts-wind flows from high pressure at the poles to low pressure at the equator

* the wind is deflected by the earths rotation called the coriolus effect*


Air masses

An airmass is a huge section of the lower troposphere that has the same kind of weather throughtout

The best source regions for airmasses

Air masse have two characteristics

temp depends on weather it comes from the tropics or polar regions

THE HUMIDITY OF THE air mass depends on wheather it comes from land or sea

Air masses are named from their source region

c-cononitinal (dry)
m-maritime (moist)

Air Masses
An air mess is a huge section of the lower troposphere that has the same kind of weather (temperature and moisture properties) throughout.
The best

Boundiries between airmasses are called fronts

Cold fronts

1) Cold air is advancing and replacing warm air

2) cold fronts are steeper and move faster than warm fronts

3) the air rises upward rapidly forming cumulonimbus

4) Heavy precipitation and thunderstorms which start and end quickly are associated with cold fronts

5) precipitition covers 75-100 miles and occurs both befor and after a cold front passes at the surface

6) cold fronts travel at speeds betweeen 25-30 MPH

7) as soon as a cold front passes the tempurature will decrease and the wind speed may rise


  • warm air is advancing and replacing cold air

  • warm fronts move slower warm air moves up a gental frontal surface

  • warm air may travel 1000 km before rising 2 or 3 km

  • First cirrus and cirrostratus clouds form from and then there are altostratus clouds finally steady rain falls from nimbostratus clouds

  • precipitation can occur for 225-275 miles ahead of where the front touches the ground

  • warm fronts travel at speeds between 20-25 MPH

  • warmer temperatures follow the passing warm front

Occuled front

  • a cold front is advancing and combining with a warm front

  • occluding fronts move the slowest of all (20MPH)

  • these fronts are associated with cirrus and stratus clouds in front of nimbostrattous and cumulonimbus clouds

  • precipitation occurs for about 400 miles most of which is in front of the frontal boundary

  • cool air is in front as warm air is forced up by the cold air which follows the passing occulding front