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Weather
An Overview
Atmosphere
 Is a mixture of the gasses that surround the
Earth.
 The atmosphere gives us the air we breath
as well as protects us from some of the
sun’s harmful rays.
 The atmosphere is also the location where
a lot of the weather phenomena that we will
be learning about happens.
Air Pressure
 Is the measure of the force with which air
molecules press on the surface.
 When your ears pop the pressure inside
your ears and outside your ears become =
Altitude
Is defined as the
height of an object
above the surface of
the Earth.
 As altitude increases
air pressure
decreases
 Why is this?

Layers of the atmosphere
Based on temperature
the Earth’s
atmosphere is divided
into 4 layers
 1) Troposphere
 2) Stratosphere
 3) Mesosphere
 4) Thermosphere

Troposphere
Lowest layer of the
atmosphere
 Densest atmospheric
layer
 Earth’s water vapor,
air pollution, clouds,
weather, and life
forms are found at this
layer

Stratosphere
The air is very thin and
contains very little
moisture
 Temp approx. -60 C
degrees
 In this layer the
temperature rises
with altitude because
of ozone which is a
gas that heats up the

Mesosphere
Coldest layer: can be
as low as -93 degrees
C
 Large wind storms can
take place with wind
speeds reaching more
than 150 mph

Thermosphere
The upper most
atmospheric layer in
which the
temperature can
reach 1700 degrees C.
 Very few molecules at
this layer
 Picture to right shows
heat at this layer

Heating of the Atmosphere
Heating of the
atmosphere takes
places in 3 ways
 1) Conduction
 2) Convection
 3) Radiation

Radiation
 This is a method of heat transfer in which
heat travels through empty space
 The best example of this is the suns rays
heating up the Earth. The heat will travel
through outer space (empty) reach our
planet and heat up the surface
Conduction
 Is the transfer of thermal energy from one
material to another by direct contact
 Example would be walking on the sidewalk
and heating up your foot from the heat that
has built up on the ground
Convection
 Transfer of thermal energy by circulation
or movement of a liquid or a gas
 For example: air is heated and it rises then
it cools and it sinks. This circular up and
down motion pushes atmospheric gases on
our planet .
“The Green House Effect”

This is the process in
which gases in the
atmosphere trap
thermal energy. Keeps
the surface of the
Earth much warmer

Global warming: This
is when the Earth’s
average temperature
increases each year.
Average temperature
is the average of all
the locations on earth
during 1 whole year.
Wind
 Is very simply defined as moving air.
 It is created from differences in air
pressure caused by temperature
differences.
 Usually there is greater pressure at the
poles and less at the equator. There fore
wind usually moves from the poles toward
the equator.
Coriolis Effect
 The curving of moving objects, such as
wind, by the earth’s rotation is called the
“coriolis effect”.
 Cont. on page 404
 Read 402 - 407
 Page 407 questions 1-4
Types of Winds
 Trade Winds: winds that blow from 30
degrees latitude to the equator
 Westerlies: wind belts found in both the
northern hemisphere and southern
hemisphere between 30 - 60 degrees
latitude
 Polar Easterlies: wind belts from the poles
to 60 degrees latitude
The Jet stream
 The jet stream is very high speed band of
air that blows in the troposphere and lower
stratosphere
 The jet stream can reach wind speeds of up
to 250 km / hr
 This stream of air switches direction often,
and in doing so steers storms / fronts
across our country
Jet Stream
Pollution

Primary pollutants:
put in the air by
human or natural
activity

Secondary Pollutants:
This type of pollutant
reacts when two
primary pollutants
react to form a new
secondary pollutant
Acid Precipitation
 When fuels get burned some of the
remnants go up into the air where it mixes
with water vapor and then comes down as
acid rain. This rain can weather metal,
wood (ect.) at and advanced rate.
 Ex. Statue of liberty, Bridges
Assignment
 In the past few decades Pollution has
become a major problem for our country.
Please write an essay stating what you
would do if you had an unlimited budget
and where in charge of environmental
policies in our country. How would you go
about fixing this major problem?
Water Cycle
 This relates to the continuous movement of
water from lakes / rivers to clouds to the
ground and back up again
 Vocabulary: condensation / vaporization
Humidity
 Is defined as the amount of water vapor or
moisture in the air.
 relative humidity: Is the amount of
moisture in the air compared to the
maximum amount of humidity it can hold at
a certain temperature
Dew Point
 Is defined as the temperature air must cool
to be completely saturated.
Clouds
 A cloud is a collection of millions of tiny
little water droplets or ice crystals which
are suspended in the air
 In this next section we are going to learn
about the different types of clouds
Cumulus Clouds
 Puffy white cloud that tend to have a white
bottom ( cotton balls)
 These clouds form when warm air rises
 They usually represent good weather,
unless they get very large they can
represent thunderstorms
Stratus clouds
 This type of cloud forms in layers
 This type of clouds covers large areas of
the sky usually blocking out the sun
 Caused by a gentle lifting of a large body of
air into the atmosphere
 NIMBOSTRATUS: clouds that are stratus in
origin however dark in color. They usually
produce light to heavy rain
Cirrus Clouds
 Thin feathery white clouds formed at high
altitudes
 These types of clouds form when the wind
is strong
 They may represent bad weather If they
begin to thicken and lower in altitude
Precipitation
 Is water in liquid or solid form that forms
from the sky to the surface of the Earth
 There are four major types of precipitation
 Rain, Sleet, Snow, Hail
 In order for a cloud droplet to form as
precipitation it must increase it’s size 100
times
Snow / Sleet
 Snow forms when water vapor is so cold
that it falls in solid form as snow
 Sleet forms when rain falls through a layer
of freezing air
 If the rain does not freeze till it hits the
surface then it forms something called
glaze or (ground ice)
Hail
 Solid precipitation that forms as balls or
lumps of ice
 Usually forms when gust of air carries rain
droplets to a high ,, cold altitude where it
freezes and then falls to the Earth as a ball
of ice called hail