Scope, Sequence, and Coordination

A Framework for High School Science Education

Based on the National Science Education Standards

Atmospheric Pressure

Global Climate: Sun’s Energy and Influence of Dynamic and Static Factors
Global climate is determined by energy transfer from the sun at and near the earth’s surface. This energy transfer is influenced by dynamic processes such as cloud cover and the earth’s rotation, and static conditions such as the position of mountain ranges and oceans.

Further Description:

Global climate refers to the average weather of the entire earth over long periods of time (between 20 or 30 years). Climate is affected by the same processes as those in weather, but the time over which data are gathered is much greater. As a result, climate patterns have been identified, and there are attempts to correlate them with some process or change. The depletion of the ozone layer and the suggested climatic effects is one example of such a correlation. The heat transfer processes associated with seasonal fluctuations in the amount of solar energy reaching a given place on Earth’s surface at a given time of year are caused by variations in the angle (inclination) of the sun’s rays and by length of daylight (rotation). Both of these effects are due to Earth’s inclination with respect to its orbital plane.

On a small scale, atmospheric conditions such as cloud cover, dust loading, and physiographic features also contribute to heat differences. Clouds are very good absorbers of terrestrial radiation and are primarily responsible for maintaining Earth’s surface temperatures during the night. A thick cloud cover will absorb most terrestrial radiation, and a portion of this radiation is returned to Earth’s surface. It is not surprising that on clear, dry nights the surface cools considerably more than on cloudy humid evenings.

Local conditions are affected, in some part, by the static features nearby. These features, such as mountains, oceans, and lakes, can modify the heat transfer process and the weather for that area. The specific heat of water, for example, provides large bodies of water with the ability to moderate climates of nearby land masses, since the water can exchange large amounts of heat with the air masses that pass over that land. Thus bodies of water form a buffer.

Concepts Needed:

Grade 9

Pressure, buoyancy, density

Grade 10

Albedo, insolation, insulation, atmospheric gases

Grade 11

Ozone, saturation, convective stability, vertical mixing, inversion, adiabatic, isothermal, isobaric, gradient

Grade 12

Climatology, warming planet, modeling, ice ages

Empirical Laws or Observed Relationships:

Stratification and lapse rates; adiabatic processes in the atmosphere; stability and instability of air masses; Coriolis effects on wind; geostrophic wind is inversely proportional to the distance between isobars; geostrophic winds flow as fluids, with no divergence or convergence.

Theories or Models:

Climatic cycles, climate models using computers

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Micro-Unit Description:

Atmospheric Pressure
Grade nine students should understand basic kinematics, velocity, and acceleration and their relationships in the context of atmospheric air masses (that contain water vapor). In this same context, they should examine pressure, temperature, the ideal gas law qualitatively, and the relationship between density of an air mass and its buoyancy. The basic concepts of heat and temperature and phase changes for water are essential.

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