9-12

F1: Describe how air pressure, temperature, and moisture interact to cause changes in the weather.

Organizing Questions	Describe why "low air pressure" is generally associated with bad weather. Describe stable and unstable air masses. Explain why dew forms, using ideas of relative and absolute humidity. Explain the basic cloud-forming process. Explain how the pressure gradient force, Coriolis effect, and friction influence wind. Discuss the differences between warm fronts and cold fronts. Describe the primary mid-latitude weather producing systems.
Elaboration	Weather is not listed as a separate coherent topic in the national documents, although the basic processes involving air temperature and pressure are covered.
Specific Ideas	Weather (in the short run) and climate (in the long run) involve the transfer of energy in and out of the atmosphere. Solar radiation heats the land masses, oceans, and air. Transfer of heat energy at the boundaries between the atmosphere, the land masses, and the oceans results in layers of different temperatures and densities in both the ocean and atmosphere. The action of gravitational force on regions of different densities causes them to rise or fall--and such circulation, influenced by the rotation of the earth, produces winds and ocean currents. Benchmark 4B2 The weather provides the most familiar example of a chaotic system. Meterologists make thousands upon thousands of measurements of wind speed, air temeprature, and barometric pressure in their efforts to predcit the weather. They do pretty well with 24-hour to 48-hour forcasts, and sometimes they even get the seven day predictions right. But no matter how fancy the measurements and the computer simulations, there is no way to guess what the weather will be a year from now. The cahoatic nature of the atmospheric motion can be graphically represetned by something called the "butterfly effect". Science Matters p. 19
Developmental & Instructional Implications	An integrated picture of the earth has to develop over many years, with some concepts being visited over and over again in new contexts and greater detail. Some aspects can be learned in science, others in geography; some parts can be purely descriptive, others must draw on physical principles. …Perhaps the most important reason for students to study the earth repeatedly is that they take years to acquire the knowledge that they need to complete the picture. The full picture requires the introduction of such concepts as temperature, the water cycle, gravitation, states of matter, chemical concentration, and energy transfer. Understanding of these concepts grows slowly as children mature and encounter them in different contexts. Benchmarks p. 66 Students experienced difficulty in coming to terms with atmospheric pressure. When asked to interpret situations involving atmospheric pressure, although pressure difference was perceivable, only 1/5 of students referred to it in accounting for the phenomena … Explanations tended to be in terms of a vacuum inside the container "sucking", pressure inside the container sucking or pulling, or an idea that spaces tend to be filled. Driver pgs. 106-107
Examples

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