Cycles of Air Temperature

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Outline for Lesson 6
World Distributions of Temperature
Cycles of Air Temperature
Temperature Measurements
2/13/03
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World Temperature Distributions
Isotherms trend east to west
(Temperature)
North
Q. Why ?
A. Heating of the Earths surface and
atmosphere is in large part a function of
latitude.
World mean sea level temperature in January in C.
South
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World Temperature Distributions
Decreasing temperature toward the Poles
(Temperature)
North
Q. Why ?
Cold
Hot
A. Heating of the Earths surface and
atmosphere is in large part a function of
latitude.
Cold
South
World mean sea level temperature in January in C.
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World Temperature Distributions
Hot and Cool spots continuously migrate south
from June 21-22 until Dec 22-23 them migrate
north from Dec 22-23 until June 21-22.
World mean sea level temperature in January in C.
Q. Why ?
World mean sea level temperature in July in C.
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Migration of position where suns rays are 90
overhead
The hot spotson the temperature plot migrate
with latitude, as does
the position where the
Suns rays are 90
overhead.
23.5 N
Tropic of Cancer
Equator
Tropic of Capricorn
23.5 S
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The higher the angle of the sun the more solar
radiation to heat the Earth and atmosphere.
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World Temperature Distributions
The hottest and coldest places are over land.
Warm ocean currents moving to the Poles warm
the air. Equatorial bound currents Help cool the
air.
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World mean sea level temperature in January in C.
World mean sea level temperature in July in C.
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Another way to think about the effect of latitude
on temperature data
Comparison of solar noon sun angles for for the
summer and winter solstice.
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Cycles of Air temperatures
Its hot in the day and cold in the night!!.
Public Enemy
Rate of outgoing exceeds the rate Of incoming.
Rate of incoming exceeds the rate of outgoing.
The daily cycle of incoming solar radiation,
earths radiation And the resulting temperature
cycle. Midday, Equinox.
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Annual Temperature Variations
The months of the year with the highest and
lowest temperatures do not coincide with the
months receiving the most or lowest radiation.
The other processes which also control
temperature (i.e. winds and surface ocean
currents do not happen instantaneously. There
is a lag time.
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Urban heat islands have been created over time
here in the United States and around the world.
In Baltimore, Phoenix, Tucson,
Washington, Shanghai, and Tokyo, for example,
scientific data show that July's maximum
temperatures during the last 30 to 80 years have
been steadily increasing at a rate of one-half to
one degree Fahrenheit every ten years.
In these cities, the temperature on the hottest
summer day is rising by up to 1F each decade.
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The Heat Island Effect (Washington DC)
Changes in the earths surface when
vegetated areas are transformed to asphalt .
Tall buildings and Concrete have a
higher specific heat than vegetation and soil
Rapid runoff of rainwater reduces the amount of
energy consumed by evaporative cooling.
Average Minimum Temperatures (Dec-Feb)
Heat that would have gone to convert liquid water
to water vapor is goes toward increasing the
surface temperature.
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Data from table 3-D on page 74
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Higher temperatures in urban heat islands results
in increased energy use, mostly due to a greater
demand for air conditioning. As power plants burn
more fossil fuels, they increase both the
pollution level and energy costs.
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As temperature rises, so does the likelihood that
ozone (and smog) will exceed the national
standard.
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Bimetal strips are often used to construct
thermographs.
A type of thermometer with two metal strips
connected together. The two metals expand at
drastically different rates when heated which
causes the stripe to bend. The bending moves
the pen up and down the roll of graph paper
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Maximum Temperature in the afternoon
Cooling trend.. Perhaps a cold front
- Maximum temperatures observed.
- Minimum temperatures observed.
Thermograph plot of temperatures for Peoria
Illinois, during a seven-day span in May 1992.
Temperature typically reaches a maximum in the
afternoon, however, a weather event results in a
cooling trend that results in the maximum being
observed near midnight.
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Temperature Measurements
Mechanical Thermometers
Temperature rises, molecules in the fluid grow
more expansive and rise in the column. Have to
account for optical distortions created by the
meniscus.calibrate it with a known standard
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Special thermometers have been developed to
record the maximum and minimum temperatures.
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Electrical Thermometers -thermistor (thermal
resistor) is a stripe of metal which varies
its resistance to a current flow with
temperature. As temperature goes down the
resistance decreases temperature goes up and the
resistance increases.
various thermistors
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Temperature Scales

• Fahrenheit
• Celsius
• Kelvin

All temperature scales need reference
points. The freezing and boiling point of water
are convenient.
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How to convert between the different scales.
The interval between the boiling and freezing
point is 100 degrees on the Celsius scale and 180
between on Fahrenheit scale.
180/100 1.8
F to C C to F
F (1.8 x C) 32 or C (F-32)/1.8
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Kelvin Scale Degrees Kelvin are called
Kelvins. The divisions are exactly the same as
Celsius. The reference points are different
however, 373 K is the boiling point and 273 is
the freezing point. The unique reference point
for Kelvin is point at which all molecular motion
is presumed to stop.
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Chapter 4 Moisture and Atmospheric Stability

• Movement of Water through the Atmosphere
• Waters Changes of State

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Movement of Water through the Atmosphere
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It is the Atmosphere which links the Oceans to
the Land. Even though the amount of water in the
atmosphere at any time is only a fraction if the
total Earths total hydrosphere, it is the rapid
exchange taking place that creates what we call
weather.
How fast is the exchange?
It is estimated that over North America, almost
six times as much water is carried within the
atmospheric currents than is transported in all
the rivers in the continent.
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Energy is absorbed or released from the
atmosphere during the exchange. The energy that
is liberated helps to drive the weather machine