Unit 2 Deciphering Short-Term Climate Variability
Making Sense of Ocean and Atmospheric Data Depicting Climate Variability
In this lesson, students will be provided with data depicting the cyclic changes in tropical Pacific climate associated with the El Niño-Southern Oscillation. Students will try to identify patterns in the data and discuss their findings with the class. An auxiliary lab or homework exercise provides students with data from the North Atlantic and guides them in identifying cyclic changes associated with the North Atlantic Oscillation.
Unit 2 Teaching Objectives
- Cognitive: Provide students with an understanding of how ocean-atmosphere interactions lead to short-term climate variability, such as the El Niño-Southern Oscillation or the North Atlantic Oscillation.
- Behavioral: Provide students with experience examining climate data from observations and formulating hypotheses regarding the cause of change.
Unit 2 Learning Outcomes
- Case Study 2.1
- Students will be able to interpret lat-lon contour plots and Hovmöller diagrams.
- Students will be able to explain how temperature and pressure anomalies affect the location of precipitation in the tropical Pacific.
- Case Study 2.2
- Practice reading lat-lon contour plots of pressure and precipitation.
- Depict changes in pressure and precipitation over time on a map of the North Atlantic.
- Explain how pressure changes and precipitation patterns may be connected.
- Be able to explain the importance of examining an anomaly.
Context for Use
Description and Teaching Materials
This unit makes use of a case study (Case Study 2.1) in which students examine year-to-year changes in temperature and precipitation (and optionally, pressure) in the tropical Pacific. The Teaching Notes and Tips below provide a suggested outline for incorporating this case study into a 50-minute lecture period. The case study in this unit is designed to provide the student with experience examining real data from the tropical Pacific. This activity follows a guided inquiry approach, in which students are provided with very little information about what they should expect to find in the data. However, they are provided with guidance on how to examine the data. Case Study 2.1 serves as a preparatory activity for Unit 3, where students learn about the El Niño-Southern Oscillation. Thus, Case Study 2.1 does not introduce students to the term El Niño, but rather focuses on identifications of patterns in the data.
For instructors who would like to give their students additional practice examining data, Case Study 2.2 is designed to be a homework or laboratory exercise (it may also be incorporated into a lecture period, if there is time available). Case Study 2.2 provides students with an opportunity to practice what they have learned in class by looking at data depicting climate variability in another part of the world, the North Atlantic. Case Study 2.2 may be combined with Case Study 3.2 for an extended lab or homework activity.
Teaching Notes and Tips
Case Study 2.1 and relevant discussion in this unit are designed to be completed in a 50-minute class period. The following is a sample 50-minute plan. To facilitate the introduction to the material, you may choose to assign all or part of the following preparation assignment to students at the end of the previous class period or online: Unit 2 Preparation Exercise (Microsoft Word 2007 (.docx) 125kB May22 14).
10 min: Provide an introduction to data collection in the tropical Pacific. (If this unit is following Unit 1 of the Climate of Change module, then refer to the previous day's discussion regarding the Incan method of climate forecasting. Indicate that we would like to understand that better.) To help students visualize data collection, show photos from shipboard collection of data along TAO array.
If students are not familiar with looking at climate data, be sure to discuss what it means to look at average data. It may be helpful to explain that we can average over various time periods (30 years, one year, one season, a month, a week, or even shorter time period), and that when looking at data, the first thing they need to consider is the time period over which the data has been averaged. They should also understand the concept of an anomaly, or a difference from the long-term average. If they are not familiar with vectors, they should be introduced to the idea that wind data may be plotted as an arrow, where the length of the arrow represents the speed of the wind.
Wind anomalies are a tough concept to grasp. It may help to explain that the arrows on the anomaly plots provided in Case Study 2.1 provide an indicator of how different the wind is from normal.
20 min: Provide students with the Unit 2 handouts and data sheets (perhaps one color data sheet per group in a large class), and have students organize into groups of three to four (depends on class size). Handouts and data sheets are available here: Case Study 2.1. The student handout includes some guiding questions to help them organize their thoughts on the data. Let students know that they will each need to turn in their handout with notes at the end of the class period (if you would like to use the handout as an assessment). Also let them know that, as a group, they should choose one reporter to provide the class an overview of their discussion (depending on the class size, this person may or may not actually have to speak). Assign each group one of three data sets: temperature/wind, precipitation, pressure.
15 min: Debrief as a class. Draw on a board, or project a copy of the chart on the student handout. Go around to each group and solicit observations to fill in the chart. As a class discuss: What are the most important observations here? What conclusions can we draw about tropical Pacific climate variability? Can we come up with any ideas about what might be causing what we see here?
5 min: Formative Assessment: Ask students to answer the questions in part 2 of the handout (What conclusions can we draw about tropical Pacific climate from the data?)
Assessments from student activity sheets:
Learning Goal #1: Student handouts for activities have questions that require students to describe locations of anomalies and identify cycles of change. Students who can complete these tasks have adequately met the first learning objective.
Learning Goal #2: In the student activity handouts, students must be able to identify cycles of change on a Hovmöller diagram or on a diagram that they create themselves. They must identify the time frame of change and the fact that there are changes.
Possible Exam Questions:
Learning Goal #1: Why do changes in the location of warm waters in the tropical Pacific affect the location of precipitation? How frequently does this change occur, and what regions experience the greatest impacts?
Learning Objective #2: Define anomaly, and explain why it is important to look at anomalies when examining climate data.
After students have completed the data analysis for Case Study 2.1, but prior to class discussion, have students, on their own, make a sketch of a vertical cross section of the tropical Pacific (i.e., tell them to imagine drawing a vertical slice through the tropical Pacific). Have them choose the year with the largest positive anomalies that they viewed in the data, and depict those anomalies in the sketch. Ask them to think about where they would expect to find other anomalies, and depict those on the sketch. For example, if a student looked at temperature anomalies, they should think about where they would expect to find precipitation or pressure anomalies in relation to the temperature anomalies.
After students have had a chance to draw on their own, as a class, draw sketches of El Niño and La Niña conditions. Have students check and correct their sketches as needed.