Understanding Earths Climate

Understanding Atmospheric CirculationBy Mikayla Waugh & Rich HedmanCalifornia Science Education Conference 10/21/2011

Model-based ReasoningThe lessons were designed to engage the learner in model-based reasoning (MBR).A model is an idea or a group of ideas that helps us understand or explain the way something works.We are going to guide you through developing your own understanding of atmospheric circulation.There are many types of modelsphysical representations, scale models, computer models, but to us, a model is a set of ideas that help us understand or explain the way something works.

2Prior KnowledgeAssumptionsConvection/density currents in fluids. Specifically: temperature density (and vice versa) and then what happens BECAUSE of thisAir is a fluid. Wind is a current of air.

1. Convection/density currents in fluids. Temperature differences produce density differences, and gravity pulls the more dense fluid downward, while the less dense fluid will be pushed upward, which can cause currents and convection cells.2. Specifically: temperature density (and vice versa)

3Phenomena: Global Cloud Motion

What patterns do you notice?Driving QuestionWhat causes the patterns in earths atmospheric circulation?

We will answer the question by developing explanatory models, from basic to complex.

Consider the EarthWhere is it usually warm on earth?Where is it usually cold on earth?

Of course, with the students, make sure they know WHY it is warm in specific locations (near the equator) and cold in other locations (specifically the poles).6Make a PredictionMake a prediction:Where would air be rising from earths surface?Where would air be sinking toward earths surface?

Make sure to have discussions with students to answer these questions.7Task 1: Basic Model

Materials: beach ball globes (prepared w/ up & down arrows), transparency strips, tape, transparency pens (red, blue, black), paper towel & water (for erasing), poster paper, poster markers (red, blue, black).

Task 1: With your group,1. Use a black transparency pen to draw the surface winds on your globe predicted by your model. 2. Now use the transparency strips to make a 3-D representation of the convection cells around the globe implied by your model. Draw arrows on the transparency strips to indicate the direction of air. Use red for warm air and blue for cold air.

8Task 1: Basic Model

Materials: beach ball globes (prepared w/ up & down arrows), transparency strips, tape, transparency pens (red, blue, black), paper towel & water (for erasing), poster paper, poster markers (red, blue, black).

Task 1: With your group,1. Use a black transparency pen to draw the surface winds on your globe predicted by your model. 2. Now use the transparency strips to make a 3-D representation of the convection cells around the globe implied by your model. Draw arrows on the transparency strips to indicate the direction of air. Use red for warm air and blue for cold air.

9Task 1: Basic ModelIn the end, students globes will look something like:

Task 1: Basic ModelIn the end, students drawings should look something like:

Basic Model:Earths air is heated differentially by the sun (warm equator, cold poles).Temp differences produce density differences in air.Gravity differentially effects air masses with different densities.Warm air rises at equator; cold air sinks at poles.The result is one large convection cell the N. and S. hemispheres.

11Compare Basic Model to Phenomena

Our Basic ModelActual Phenomena

Our basic model has a problem! We need more data.Data: Earth is Big!Because earth is so big, warm air rising at the equator cools well before it reaches the poles.This air at altitude doesnt reach the north pole, it cools and sinks long before it reaches the pole.

Earth is Big! (Cont.)Also, because earth is so big, cold air sinking at the poles warms well before it travels back to the equator.This surface air doesnt reach the equator, it warms up and rises well before it reaches the equator.

Task 2: Revise the Basic ModelTask 2: With your group,1. Discuss how to best revise your model to take into account that earth is large. 2. Then use the transparency strips to make a 3-D representation of the convection cells around the globe implied by your model. Draw arrows on the transparency strips to indicate the direction of air. Use red for warm air and blue for cold air.3. Be prepared to share and explain your model.

Materials: beach ball globes, transparency strips, tape, transparency pens (red, blue, black), paper towel & water (for erasing), poster paper, poster markers (red, blue, black).

15Task 2: Revise the Basic Model (Cont.)4. On poster paper, sketch a circle for earth, and draw in your convection cells and your predicted surface air currents. Use red for warm air and blue for cold air.Task 2: Share & Explain Group ModelsGroups share and explain their revised basic models.After discussion, develop a class consensus model that fits the data we have so far.

If all groups have the three cell model allow them to work up until 45 minutes in the presentation. If there is a mixture of 2-cell and 3-cell models, stop the groups at 37 minutes for discussion to allow everyone to come to the 3-cell model.17Class Consensus ModelThe class consensus model should look something like:

You may want to tape the loops together at the 30 and 60 degree lines. Sometimes the students will think that the air could rise or sink between the loops, and by taping them together, you can help reinforce that the two air masses are coming together and moving in one direction.18

Compare Class Model to PhenomenaOur Class ModelActual Phenomena

Our model still has a problem! We need YET MORE DATARevised Basic Model:Earths air is heated differentially by the sun (warm equator, cold poles).Temp differences produce density differences in air.Gravity differentially effects air masses with different densities.Warm air rises at equator; cold air sinks at poles.Because the earth is so large, the density differences produce 3 convection cells in the N. hemisphere and 3 in the S. hemisphere.

19Data: Earth is Spinning!Earths spin is counter-clock wise (CCW) when viewed from the North Pole.Earths spin is clockwise (CW) when viewed from the South Pole.

CCWCW

Our models correctly take into account that the suns differential heating of earth ultimately produces the surface wind patterns we observe.Our consensus model also correctly takes into account earths large size, which results in 3 convection cells in each hemisphere.But our model does not take into account earths spin.

20Data: Earth is Spinning!While watching, pay attention to the data patterns.If spinning clockwise, the ball is deflected?If spinning counter-clockwise, the ball is deflected?

Task 3: Final ModelHow would this affect the wind directions on your model? Draw in the deflections you predict will occur on your poster.

22Task 3: Final ModelHave a group or two share their final model.

Now lets look at the scientific consensus of the wind patterns23Final Model Surface WindsFinal Model

N. Hemisphere winds deflected to the right of original path.S. Hemisphere winds deflected to the left of original path.Final Model Surface WindsFinal Model

In both hemispheres,

poleward wind is deflected to the EAST,

and

equatorward wind is deflected to the WEST.Alternatively:

Representation of Final Model

Final Model:Earths air is heated differentially by the sun (warm equator, cold poles).Temp differences produce density differences in air.Gravity differentially effects air masses with different densities.Warm air rises at equator; cold air sinks at poles.Because the earth is so large, the density differences produce 3 convection cells in the N. hemisphere and 3 in the S. hemisphere.Earths spin deflects poleward wind west and equatorward wind east.

26Compare Final Model to PhenomenaFinal ModelActual Phenomena

Our final model predicts the actual wind patterns!Simple Version of Final ModelOur simple model which explains earths atmospheric circulation:

Uneven heating of earth + earths large size + earths spin rate => observed global wind patterns.

We can describe the causal relationships within this model in much more detail . . . (next slide)Detailed Model (teacher only!)

Linked to Earth Sci Stds 5 & 6:5. Heating of Earths surface and atmosphere by the sun drives convection within the atmosphere and oceans, producing winds and ocean currents. As a basis for understanding this concept: a. Students know how differential heating of Earth results in circulation patterns in the atmosphere and oceans that globally distribute the heat. b. Students know the relationship between the rotation of Earth and the circular motions of ocean currents and air in pressure centers. c. Students know the origin and effects of temperature inversions. d. Students know properties of ocean water, such as temperature and salinity, can be used to explain the layered structure of the oceans, the generation of horizontal and vertical ocean currents, and the geographic distribution of marine organisms. e. Students know rain forests and deserts on Earth are distributed in bands at specific latitudes. f.* Students know the interaction of wind patterns, ocean currents, and mountain ranges results in the global pattern of latitudinal bands of rain forests and deserts. g.* Students know features of the ENSO (El Nio southern oscillation) cycle in terms of sea-surface and air temperature variations across the Pacific and some climatic results of this cycle. 6. Climate is the long-term average of a regions weather and depends on many factors. As a basis for understanding this concept: a. Students know weather (in the short run) and climate (in the long run) involve the transfer of energy into and out of the atmosphere. b. Students know the effects on climate of latitude, elevation, topography, and proximity to large bodies of water and cold or warm ocean currents. c. Students know how Earths climate has changed over time, corresponding to changes in Earths geography, atmospheric composition, and other factors, such as solar radiation and plate movement. d.* Students know how computer models are used to predict the effects of the increase in greenhouse gases on climate for the planet as a whole and for specific regions.

Thank you!Contact information:Rich Hedmanhedmanrd@csus.eduMikayla Waughmikaylaw@vacavilleusd.org

These lessons resulted from teacher collaboration during the 2009-2010 school year supported through a UC Davis / National Science Foundation grant.The program is called Innovations in Science Instruction through Modeling (ISIM), which is coordinated by the Sacramento Area Science Project (SASP).

Assessing Student UnderstandingOne option:Use our final model of atmospheric circulation to explain earths surface wind directions in each band of latitude.Assessing Student UnderstandingAnother option:Use our final model of atmospheric circulation to explain the high pressure at the poles and 30 latitude lines and low pressure along the equator and 60 latitude lines:

Extensions or AssessmentEven with the simple model:Uneven heating of earth + earths large size + earths spin rate => observed global wind patterns

We can ask a lot of interesting questions:What happens if we vary the planets spin rate?What happens if we change the spin direction?What happens if we have a small planet?What happens if we have a giant planet?What happens if the temperature differential is greater?What happens if the temperature differential is less?Extension Example: Jupiter Winds

Extension Example: Other Planets

Ok, Thats Really the End!Contact information:Rich Hedmanhedmanrd@csus.eduMikayla Waughmikaylaw@vacavilleusd.org

These lessons resulted from teacher collaboration during the 2009-2010 school year supported through a UC Davis / National Science Foundation grant.The program is called Innovations in Science Instruction through Modeling (ISIM), which is coordinated by the Sacramento Area Science Project (SASP).