Download M Ch 3 Cornell Notes Teacher

Chapter 3: Temperature
Objectives
• Identify the different ways to record temperature.
• Describe why temperatures vary.
• Describe how temperatures around the world are different.
• Explain the cycles of air temperature.
• Identify the different ways temperature is measured.
• Compare the different temperature scales.
• Explain how meteorologists use temperature data.
For The Record: Air Temperature Data
• When someone asks about the day’s weather, air temperature is often the first
element mentioned.
• And we know from experience, that temperatures change over different time
scales: seasonal, daily, even hourly.
• We also know, from TV weather broadcasts, that weather around the world can
be very different.
• Temperature data are gathered at thousands of manned and automated weather
stations world-wide; and at many of these stations, only maximum and minimum
temperatures are recorded.
• The Daily Mean Temperature is determined by adding the high & low
temperature and dividing by 2; and the Daily Temperature Range is the
difference between the high & low temperature.
• Along with daily temperature measurements, meteorologists will gather monthly
& yearly temperature averages.
• The Monthly Mean Temperature is calculated by adding the daily means for each
day of the month, and then averaging by the number of days of the month in
question.
• The Annual Mean Temperature is the average of the 12 monthly means.
• Annual Temperature Range is the difference between the warmest & coldest
Monthly Mean Temperatures.
• Meteorologists will use the past mean temperatures to help predict what kind of
weather we are likely to face in the future, and to track possible climate change in
a particular area.
• Meteorologists use isotherms to look at the
distribution of
temperature over
a large area.
• An Isotherm is the
line that connects
points on a map
that have the same
temperatures.
• So, all points
that an isotherm
passes through
have the same
temperatures at
that point in time.
Name_________________
Date_____/_____/_______
Hour___
For The Record: Air Temperature Data
• Often times 5o to 10o temperature intervals are used, but any interval can be used.
• Isothermal maps are valuable tools because they show differences in temperature
quickly and clearly.
• Areas of high and low temperatures are easy to see and understand.
• Isothermal maps also easily show the Temperature Gradient: the amount of
temperature change over a certain distance.
• Isothermal lines that are closely spaced indicate a quick change in temperature.
• Whereas, lines that are spaced far apart indicate a more gradual change in
temperature.
Controls Of Temperature
• The Controls Of Temperature are factors that cause temperature changes
depending on time and place.
• Latitude (how far north or south something is) may be the most influential factor
effecting temperature.
• But latitude isn’t the only thing effecting temperature; differential heating of land
and water, ocean currents, altitude, geographic position, and cloud cover also
influence temperature change.
Controls Of Temperature: Land & Water
• Temperature variations on Earth depend
on areas heating up at different rates, and
land & water heat up at very different rates.
• Land heats up more rapidly and to higher
temperatures than water, and it cools more
rapidly and to lower temperatures than water.
• Four factors are responsible for land and water
heating up and cooling off at different rates.
1. Water moves around a lot and this
movement quickly causes heat to be
distributed evenly over a large area.
2. Because water is transparent,
sunlight to penetrates farther than
it does with soil (which allows heat
to penetrate only a few centimeters
below the surface).
3. The specific heat of water is 3
times greater than land; meaning
that water needs more energy to
raise its temperature than land does.
4. Way more evaporation (a cooling
process) occurs with bodies of
water, than with land surfaces.
• All together these factors mean that
water warms more slowly, and holds
greater amounts of heat for longer periods of time.
• This explains why two cities that are located at the same latitude, like Vancouver
(marine) and Winnipeg (continental), can have different mean temperatures
throughout the year.
Controls Of Temperature:
Ocean Currents
• Another factor that
controls temperatures
throughout the world
are ocean currents.
• The reason why the
equatorial region stays
warm all the time is
because that region gets
direct sunlight year round.
• Regions that are closer
to the north and south
poles, however, get direct sunlight for only
part of the year; and so they have a greater range of temperature.
• There is a net gain of energy closer to the equator and a net loss of energy closer
to the poles.
• Because the equatorial region is not getting warmer every year, and the
polar regions are not getting colder every year; there must be a transfer
of energy from areas with a lot of heat to areas with little heat.
• Ocean currents are driving this energy transfer.
• The transfer of energy by ocean
currents equalizes the temperature
differences between these regions.
• The Gulf Stream is an ocean current that
flows from the Gulf of Mexico up past
England bringing warm moist air that
keeps most of Europe’s climate mild.
• Warm ocean currents bring warm
water to the poles, and cold current
bring cold water to the equator.
Controls Of Temperature: Altitude
• Altitude is also important to an area’s
temperature, because the temperature
drops 6.5oC per kilometer up.
• When a location is higher up, the
atmospheric density & pressure
will be lower.
• This means that there is not as many
molecules to absorb heat as there are
at lower elevations, which also means
that solar radiation intensity is higher.
• Temperatures ranges will be greater
at higher altitudes.
The Controls Of Temperature: Geographic Position
• The location of an area on the globe also influences its temperature
range.
• For example, a coastal location where the winds blow from the ocean onto the
shore (a Windward coast) will have cool summers and mild winters.
The Controls Of Temperature: Geographic Position
• Whereas, a coastal location where winds blow from land out to sea (a Leeward
coast) will have a climate more consistent with other locations on the continent it
occupies.
The Controls Of Temperature: Cloud Cover & Albedo
• Have you ever noticed that clear days
are just a little bit warmer than cloudy
days, and clear nights are just a little
bit colder than cloudy nights?
• That’s because clouds act as insulation
for Earth: reflecting sunlight away from
the surface during the day (called Albedo).
• And at night, clouds hold heat in close
to Earth instead of letting it radiate
back into space.
World Distribution Of Temperatures
• From hot colors near
the equator to cool
colors near the poles,
the two isothermal
maps shown here
indicate sea-level
temperatures at the
seasonally extreme
months of January
and July.
• These maps illustrate
one key idea: latitude
has a great deal to
do with how well
sunlight heats up
the Earth’s surface
at different times
of the year.
• We see Earth’s
warmest area in
January are south
of the equator, and eventually shift north by July; with the isothermal
lines generally running more east / west, than north / south.
• And continental areas have greater temperature shifts than ocean areas, with the
greatest temperature shifts on Earth happening in eastern Russia (-43oC to 20oC =
-45oF to 68oF ).
Cycles Of Air Temperature
• Of course, we also experience the daily rise and fall of temperatures, because of
the Earth’s rotation.
• During this daily cycle, the time the highest daily temperatures are recorded does
not generally coincide with the time the maximum amount of solar radiation is
received.
Cycles Of Air Temperature
• The maximum amount of solar
radiation is received at noon,
but the high temperature for
the day is often around 5pm.
• Of course, we also experience the
daily rise and fall of temperatures,
because of the Earth’s rotation.
• During this daily cycle, the time
the highest daily temperatures are
recorded does not generally
coincide with the time the maximum
amount of solar radiation is received.
• The maximum amount of solar radiation is
received at noon, but the high temperature
for the day is often around 5pm.
• Meteorologists call this temperature
delay lag of the maximum.
Temperature Measurement
• Most substances expand when heated and
contract when cooled, and this is the basic
concept behind the standard thermometer.
• We have used the basic liquid-in-glass
thermometer since the 1600s.
• The fluid in a thermometer will expand
when warmed up (causing it to rise in the
tube), and contract when cooled down
(causing it to drop in the tube).
• Over the years, meteorologists have
developed a variety of instruments to
measure temperature, but most still
operate under the principle of
expansion and contraction.
Temperature Scales
• In the U.S. temperatures are measured in
degrees Fahrenheit, but the rest of the world
measures temperatures in degrees Celsius.
• Celsius is easy to use, because the base
temperatures are measured in factors
of 10 relative to water (0oC for freezing
and 100oC for boiling).
• The scientific community uses a third
temperature scale that is relative to
molecular motion within an object,
called the Kelvin (or absolute) scale.
• The Kelvin scale cannot have a
negative value, because 0 is
when molecules stop moving.
Wind Chill: The Power Of Moving Air
• Here in Oklahoma, we are very familiar with the effect blowing wind has on cool
air.
• We know that if the wind would only stop blowing the low temperatures could be
more bearable.
• A strong wind can pass through regular clothes and cool down areas warmed up
by body heat.
• It also blows away warm air next to the body and replaces it with cold air.
• This chart shows the time it takes for wind speed and low temperatures to effect
the time it takes for skin to suffer frostbite.
• This chart also takes into account wind two meters off of the ground, and it more
accurately portrays the body heat-loss estimates.