GEOG102_Week4Lab

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Oregon State University, Corvallis *

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102

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Geography

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Apr 3, 2024

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docx

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GEOG 102 Module 4 Lab: El Niño or La Niña? Overview The El Niño Southern Oscillation (ENSO) affects weather worldwide, influencing droughts, hurricanes, rainfall, and flooding. The shifts in sea-surface temperature and the trade winds also affect fishing conditions off the coasts of Ecuador and Peru. Scientists have a good understanding of the effects of ENSO but are currently unable to predict the occurrence of an ENSO more than one season ahead. Application To understand patterns and changes in ocean temperatures, researchers use maps with isotherms. You are the lead climatologist for the Southern California Water District. You will use data from the Tropical Atmosphere Ocean Project (TAO) to create an isotherm map of subsurface temperatures in the tropical Pacific Ocean. The TAO project, operated by NOAA, has an array of 70 moored buoys that monitor surface temperature, rainfall, and wind, as well as ocean temperatures from 1 m to 500 m, ocean chemistry, and currents (Figs 1 and 4). The Japan Agency for Marine-Earth Science and Technology operates the Triangle Trans-Ocean Buoy Network (TRITON) buoys. The TAO buoys are in the eastern and central Pacific (blue dots), and the TRITON buoys (yellow dots) are in the western Pacific. Objectives  Graph ocean temperatures.  Identify the location of the thermocline.  Determine the difference between El Niño and La Niña events. Grading Policy The points shown for each question indicates how many sentences or elements should be included in the answer. For example, a 3-point “explain why”-type question should have an answer composed of at least 3 substantial sentences. Answers will be graded on accuracy and completeness. The instructor and TAs reserve the right to apply a penalty for submissions in which answers are hard to find or illegible, so make sure your answers are numbered accurately and delete extraneous question text prior to uploading your lab for grading. Late Lab Policy: Everyone receives ONE no-questions-asked “3-day late pass” for a lab submission with no penalty up to 3 days after the due date. You must complete and submit the lab and indicate your use of this late pass in your submission comments . No need to ask permission ahead of time. This late pass is valid for LABS ONLY. Additional late labs are accepted up to 3 days late with a penalty: 10% deduction within the first 24 hours after the due date, 25% deduction within 48 hours, and 50% deduction within 72 hours. Assignments will not be accepted after 3 days except in extraordinary circumstances when you have adequately communicated with the instructor. Note on Academic Honesty: The written and online components for this week's lab are to be done on your own. Working together with classmates is acceptable and encouraged, but the work you turn in must be your own words . Refer to the course syllabus and the OSU General Catalog for the university policies concerning academic dishonesty. Evidence of academic dishonesty could result in a zero on the assignment, failing the course, and/or a report to the university. GEOG 102 Module 4 Lab 1

Part A (40 pts) Procedure: Patterns of Ocean Temperatures (33 pts) In Part A of this Lab, you will use data from the TAO/TRITON buoy array (Figure 1 in this document) to determine whether El Niño or La Niña conditions were present during two different years. In order to figure this out, you’ll need to first analyze temperatures in the top layer of the ocean. Questions 1-4 will have you contour ocean temperature data by drawing isotherms. An isotherm is a line of equal temperature (“iso” means equal and “therm” means temperature) and these are useful for analyzing spatial patterns and variability. If you’re unfamiliar with contouring and drawing isolines, I recommend watching the videos on the Lab 4 Guidance page. You have two options for completing Questions 1-4:  You can draw on the diagrams in a digital art program or using MS Word's drawing tools, or another program of your choice.  Alternatively, you can print them, use colored pencils, photograph the result, and insert it into your text document. 1. [10 pts] On Figure 2 on page 5 of this document, draw isotherms as described in the steps below: a. The 26°C isotherm has been started between 140° E and 180°. Study the temperature values on either side of the line to understand why the line was drawn in this location. For example, in the first column between 140° E-150° E, the temperature is 27.3°C at 50 m and 25.1°C just below that. The 26°C isotherm is drawn between these two values because 26°C falls in this range. Notice how the line is slightly closer to 25.1°C than to 27.4°C. This is because 26°C (the isotherm we are drawing) is closer to 25.1°C (0.9°C away) than to 27.3°C (1.3°C away). See drawn on graph (Figure 2) below!!! b. Continue the 26°C isotherm across the Pacific Ocean to 90° W: Find a pair of values in each column that are greater and less than 26. See drawn on graph (Figure 2) below!!! c. Draw the 23°C, 20°C, 17°C, 14°C, 11°C, and 9°C isotherms. See drawn on graph (Figure 2) below!!! d. Using your method of choice, shade the areas between the isotherms, using the key below, or a similar color scheme: Table 1: Color key for shading. Temperature Range (°C) Suggested Color >26 Red 24-26 Orange 20-24 Yellow 17-20 Light Green 14-17 Dark Green 11-14 Light Blue 9-11 Dark Blue GEOG 102 Module 4 Lab 2

<9 Purple 2. [10 pts] On Figure 3, draw the 26°C, 23°C, 20°C, 17°C, 14°C, 11°C, and 9°C isotherms and shade the areas between them using the same method as in Question 1. See drawn on graph (Figure 3) below!!! 3. [1 pt] On Figure 2, at what longitudes do you find sea surface temperatures (SSTs) greater than 26°C? What about on Figure 3? On figure 2, all the longitudes have SSTs greater than 26C. For figure 3, anything to the West of the 170W longitude is greater than 26C. 4. [1.5 pts] Would you expect to find relatively high or low surface air pressure over these regions of warm SSTs? Explain your answer. With warmer SSTs, we can expect to find relatively lower pressures because the warm air rises, and the warmer surface of the water produces relatively low air pressure conditions. 5. [2 pts] On Figure 2, which direction is the wind blowing? What about on Figure 3? In figure 2, the wind is blowing from West to East. In figure 3 it’s blowing East to West. 6. [1.5 pts] Does Figure 2 show El Niño or La Niña conditions? What evidence supports this? Figure 2 depicts El Nino conditions because the temperature of the water is higher when it’s closer to the equator. 7. [1.5 pt] Does Figure 3 show El Niño or La Niña conditions? What evidence supports this? Figure 3 shows La Nina conditions because the temperature of the water is colder when it’s closer to the equator. 8. [1 pt] On Figure 2, what range of longitudes would support the strongest convection at the surface and the highest rainfall? The 150E longitude would. 9. [1.5 pts] On Figure 2, what range of longitudes and over which part of the Pacific Ocean (north, south, east, or west) would experience drought conditions? Explain your answer. The western Pacific west of the 170W longitude. 10. [2 pts] On Figure 3, at what range of longitudes would you find the best fishing? Explain your answer. East of the 140W because it has warmer mean temperatures and change in thermocline layer because this layer’s depth determines the amount of nutrients that reach the shallow depths of the water. 11. [2 pts] The thermocline is a layer of water where temperatures change rapidly with depth. To find the thermocline, look for the region where the isotherms are close together. Identify the thermocline on both Figure 2 and Figure 3 and compare them. Explain how the depth and slope of the thermocline near the South American coast changes between El Niño and La Niña conditions. During La Nina, there is upwelling which causes the thermocline near the South American coasts to come up from shallow depths. In El Nino, the water near the Eastern Pacific is warm while the Western Pacific Ocean is cold, which causes the thermocline to go down near the coast of South America which in turn causes a lack of nutrients in the surface of the water which affects the fishing industry. GEOG 102 Module 4 Lab 3

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