Download Activity 5B- Full of Hot Air

Activity 5B- Full of Hot Air
Unit-5 Atmosphere
Background Information for the Teacher
Activity
In this hands-on
activity, learners
create a model to
demonstrate the
pattern of movement
in the Earth’s
atmosphere of warm
and cold air masses.
The model further
helps to illustrate how
heat is distributed
around the globe.
NSES
Physical Science Std
B:
Energy is transferred
in many ways.
Heat moves in
predictable ways,
flowing from warmer
objects to cooler ones,
until both reach the
same temperature.
The sun is a major
source of energy
for changes on the
earth's surface. The
sun's energy arrives
as light with a range
of wavelengths,
consisting of visible
light, infrared, and
ultraviolet radiation.
247
NSES
Earth Science Std D
Clouds, formed by the
condensation of water
vapor, affect weather
and climate.
The atmosphere has
different properties at
different elevations.
The sun is the major
source of energy for
phenomena on the
earth's surface, such as
growth of plants, winds,
ocean currents, and the
water cycle. Seasons
result from variations
in the amount of the
sun's energy hitting the
surface, due to the tilt of
the earth's rotation on its
axis and the length of the
day.
CLEP
2A: Earth’s climate is
influenced by interactions
involving the Sun, ocean,
atmosphere, clouds, ice,
land, and life.
2F: The
interconnectedness of
Earth’s systems means
that a significant change
in any one component of
the climate system can
influence the equilibrium
of the entire Earth
system. Positive feedback
loops can amplify these
effects and trigger
abrupt changes in the
climate system.
5A: The components
and processes of
Earth’s climate system
are subject to the same
physical laws as the
CLEP
rest of the Universe.
1A: Sunlight reaching the Therefore, the behavior
Earth can heat the land,
of the climate system
ocean, and atmosphere.
can be understood
Some of that sunlight is
and predicted through
reflected back to space by careful, systematic study.
the surface, clouds, or ice. 5E: Scientists
Much of the sunlight that have conducted
reaches Earth is absorbed extensive research
and warms the planet.
on the fundamental
1D: Gradual changes in
characteristics of the
Earth’s rotation and orbit
climate system and
around the Sun change
their understanding will
the intensity of sunlight
continue to improve.
received in our planet’s
polar and equatorial
regions.
ELF
Atmosphere 4:
Atmospheric
circulations transport
matter and energy.
Atmosphere 4a: Energy
is exchanged between
the atmosphere and
other Earth systems
via evaporation and
precipitation of water,
radiative transfer, and
thermal convection.
Atmosphere 4b:
Unequal heating
of Earth’s surface
produces movement in
the atmosphere.
Activity 5B- Full of Hot Air
Unit-5 Atmosphere
The distribution of heat around the globe is not even. As shown in this net radiation diagram below, the
equatorial regions of the Earth receive more energy than the polar regions. This inequality is due to the fact
that the Earth is a sphere and not a flat plane.
A second reason also contributes to the unequal heating of the Earth’s surface and Oceans: Earth’s axial
tilt. For example, have you ever wondered why the average January temperature is warmer in Texas than in
Michigan? The explanation is that Earth is tilted relative to the plane of the orbit around the sun. This angle
means that in the winter in the Northern Hemisphere, more hours of sunlight reach Texas than Michigan and
the sunlight is at a higher angle, so the heating is more intense. (see graphic on next page)
Source: NASA EOS article http://earthobservatory.nasa.gov/Features/ACRIMSAT/acrimsat_3.php
248
Activity 5B- Full of Hot Air
Unit-5 Atmosphere
source: http://www.srh.noaa.gov/jetstream/global/global_intro.html
Systems in nature want to even out the distribution of heat, and the Earth as a system is no different. The
constant, unending movement of air and water among Earth’s surfaces, oceans, and atmosphere redistributes
heat (thermal energy) around the globe. Was this not the case, the Earth would undergo extreme temperature
fluctuations like that of the Moon.
The ocean and atmosphere are a coupled, or interlocked, system. They share common characteristics in that
they both are fluids and they can re-distribute heat energy and matter via convection. The global wind system
has been observed, diagrammed, and discussed for many centuries. George Hadley, in 1735, was the first to
propose a global system of convection cells that stretch from the poles to the equator. These cells form due to
temperature and density differences in the atmosphere. As the sun warms the air in the tropics, it becomes less
dense and flows upward. While the warm air is rising, it loses heat and moisture in the process of creating large
tropical storms. This cooling air flows northward, and gradually begins sinking. At the same time, cold, dense air
is sinking at the poles and flowing southward towards the equator. That volume of air is replaced by air from the
tropics. If Earth did not rotate on its axis, there would only be one of these cells in each hemisphere. However,
the rotational forces of the Earth cause a deflection in the moving air, creating not one, but three Hadley cells,
shown in the diagram at the beginning of this unit. These large convection cells drive the global winds, while
creating our weather patterns and subsequent climate regions.
249
Activity 5B- Full of Hot Air
Unit-5 Atmosphere
As a result of the Hadley Cells, there are three major global wind systems: polar easterlies, prevailing
westerly’s, and the trade winds. These large, planetary-scale winds travel thousands of kilometers over time
periods of weeks to months. These winds are what carried the great sailing vessels of the world discoverers
in the past, as well as the ocean sailors of today.
Where the ocean and atmosphere are in contact kinetic energy (energy of motion) is passed from the moving
air to the ocean surface via friction. This frictional force drives the ocean surface currents. The shallow
surface ocean currents move in tandem with the wind. The surface currents move approximately 25% of the
heat around the globe while the air currents move the other 75%.
References:
Lutgens, Edward J. Tarbuck, Frederick K. The Atmosphere: An Introduction to Meteorology. New Jersey:
Prentice Hall, 2010.
NWS Jetstream http://www.srh.noaa.gov/jetstream/global/circ.htm
Glossary
Unit
Activity
Atmosphere
Full of Hot Air
Vocabulary
Word
Convection
currents
Atmosphere
Atmosphere
Full of Hot Air
Full of Hot Air
Density
Equatorial
Atmosphere
Full of Hot Air
Equinox
Atmosphere
Atmosphere
Full of Hot Air
Full of Hot Air
Latitude
Polar
Definition
One of the major modes of heat transfer by the
movement of mass, liquid or gas.
The calculated mass per unit volume of a substance.
Less dense fluids and gases float on more dense fluids
and gases unless they mix. Hot air is less dense than
cold air which is why a hot air balloon rises.
Refers to the Equator of the Earth.
Occurs twice a year on a day in March and September,
when the tilt of the Earth is neither towards, nor away
from the sun. On these two days, the day length and
night length equal 12 hours.
Circular lines around the Earth that measure the angular
distance from the Equator in degrees. The Equator is 0o
latitude, and divides the Earth into the Northern and
Southern hemispheres.
Refers to the regions of the Earth near the poles.
Solstice
An event that occurs twice a year when the sun reaches
the most northern and most southern extremes.
Atmosphere
Full of Hot Air
250