Transcript Earth Science Honors - Unit 5 -Intro to weather-3

Earth’s Weather
Layers of the Atmosphere
 Earth’s atmosphere is divided into five layers. It
is thickest near the surface and thins out with
height until it eventually merges with space.
Layers of the Atmosphere
 Troposphere – The first layer above the surface, contains half
of the Earth's atmosphere. Weather occurs in this layer.
 Stratosphere - Many jet aircrafts fly in this layer because it is
very stable. The ozone layer absorbs harmful rays from the
sun, and gets hotter higher.
 Mesosphere - Meteors or rock fragments burn up in this
portion of the atmosphere.
 Thermosphere - This is the layer with auroras also where the
space shuttle orbits. Heats up as it gets higher due to
absorbing high energy radiation.
 Exosphere – This is the area where the atmosphere merges
into space, this area is extremely thin.
Explanations of Weather
 What causes weather?
– Heat transfer
 Convection (Main cause)
 Conduction
 Radiation
– Changes of state in the water cycle transfer energy too
 Ex: Precipitation, evaporation & condensation
Weather
 As a result of heat and moisture differences air
that lingers over an ocean or desert will become
dry or humid matching the surface below.
Four Main Air masses that effect us
 1) Continental polar air mass
– over Northern Canada and Alaska
 2) Maritime polar air mass
– over North Pacific Ocean
 3) Maritime tropical air mass
– over the Gulf of Mexico and Caribbean
 4) Continental air mass
– over the southwestern states and Mexico
Air Masses
Air and pressure
 Gas molecules in air are
constantly moving and
pushing on each other
causing air pressure.
Air pressure is measured
with a barometer.
Mercury barometers use a
glass tube of mercury. Air
pressure forces the mercury
up the column and its height
is measured.
Air pressure
Aneroid barometers use thin metal cans with most
of the air pumped out of them. The shape of the
can changes as the air pressure does, which
moves a needle or pen on a chart.
Units of pressure:
The height of the mercury column can be
measured in inches or millimeters.
Sea level air pressure: 1013.2 mb or 29.92 inches Hg.
Decreasing pressure often means a storm is
approaching.
Types of pressure
 The uneven heating of the earth
results in uneven different
temperatures and pressures on
the earth
 Look at a weather map – "H" marks areas that have
high pressure
 High pressure areas are
generally produce to clear skies
 High pressure prevents water
vapor from rising to form clouds
– "L" marks the low pressure
 low pressure areas often
produce clouds & precipitation
Wind
– Air moves from high pressure to low pressure
 The closer a high and low pressure areas
are to each other, the stronger the winds
– Winds in a high pressure area
 move clockwise
– Winds in a lower pressure area
 move counter-clockwise
Weather Fronts
When air masses meet a front develops
– Fronts are where cold and warm air meet, they can
produce weather and violent storms.
– Over time wind brings air to equalize the pressure when
a high pressure collides with a low pressure area.
Types of Fronts
 1) Warm Front
– The lighter warm air
slips over the heavier
cold air forming a
gradual slope.
– Clouds increase and
become drop in height.
– Can produce steady
Types of fronts
2) Cold Front
– Heavier cold air shoves
under the lighter warm air
 This pushes the warmer
wetter air up very fast
condensing the
moisture with it causing
clouds to form.
 Often Leads to violent
Types of fronts
 3) Stationary Front
– Neither the cold or warm air is advancing
– Often trap storms in place for extended periods
Technology
 Humans can use technology to
predict the weather
– Thermometers - temperature
readings
– Barometers - air pressure
– Hygrometer - relative humidity
– Wind Vanes - direction of wind
– Anemometer - speed of wind
– Rain gauge - amount of rainfall
– Weather satellites, weather
planes, weather balloons, and
radar - are used for measuring
many weather components.