Unit 2 Study Guide: Practice Deciphering Maps

How to Look at Data

In examining graphs, charts, or maps that contain a lot of information, such as the TAO/TRITON data maps, there are a few strategies you might use to help you decipher the most important information presented in the figure:

1. Look at the axis labels first! These will help orient you. If you are looking at a graph, they will tell you what data you are viewing. If your axis labels are latitude and longitude, they will tell you what part of the world you are looking at.
2. If you are looking at a map, the data are usually contoured, and there will be a label at or near the top of the map to tell you what you are looking at (e.g., "Sea Surface Temperature").
3. On a map, once you know what type of data you have, identify the locations with the highest and lowest values. Be sure you can name a geographical location where these occur, so that you could describe these data to someone else, if you had to (e.g., "Equatorial Western Pacific," or "Indonesia").
4. After identifying the highs and lows in data values, see if you can identify any patterns in the data. For example, do all the high values occur over land, and low values over the ocean? Or perhaps all the high values occur north of the equator, and all the low values occur south of the equator?
5. After you have enough time to study what the map or figure is presenting to you, take some time to think about why you see the patterns you do in the data. This is where you become a scientist and develop hypotheses!

This study guide below provides more opportunities to test your understanding of some of the concepts you have learned, as well as your ability to decipher new data and practice new vocabulary. Use this guide to help organize your knowledge. Test yourself by quizzing yourself on the terms with the definitions hidden below and by answering the concept questions.

New Vocabulary or Terminology

• anomaly
  Show me the definition
  Hide
  An anomaly is calculated by looking at the difference between a value at a given time and a long-term average. In studies of climate, anomalies help us identify changes from the norm.
• latitude vs longitude
  Show me the definition
  Hide
  Latitude lines are the horizontal lines on a globe that begin with 0 at the equator and increase to 90 at the north or south poles. Longitude lines are the vertical lines on a globe that begin with 0 at the Greenwich Meridian (goes through England) and increase toward the east.
• hovmöller diagram
  Show me the definition
  Hide
  This is a common way to plot meteorological data that usually has latitude on the x-axis and time on the y-axis. This type of diagram is particularly useful for helping us see cyclic changes in data over time.

Conceptual Questions

1. 

   ×

   Figure 1: Tropical Pacific Sea Surface Temperature

   Provenance: NOAA Office of Satellite and Product Operations
   Reuse: This item is in the public domain and maybe reused freely without restriction.
   Figure 1 to the right depicts ocean surface temperatures. In one or two sentences, summarize the most important information provided to you in this image (i.e., what can you learn about the ocean from looking at this data?).
   Show me what I should see in this image
   Hide
   There are many features in this image that you could comment on. Probably the most significant feature in this image is the cold water hugging the coast of South America, and the tongue of cold water that extends along the equator out into the Pacific. The temperature along this equatorial cold water can vary considerably from year to year.
   
   
   
2. What type of information is provided to you in Figure 2? How much time is represented on the y-axis? What is on the x-axis of each panel in the figure? What is the advantage of presenting information this way?
   

   ×

   Figure 2: Time evolution of zonal winds, sea surface temperatures, and thermocline depth in the tropical Pacific.

   Provenance: NOAA TAO
   Reuse: This item is in the public domain and maybe reused freely without restriction.
   Show me what I should see in this image
   Hide
   This figure presents three panels with data from the TAO/TRITON array in the tropical Pacific. The diagrams are Hovmöller diagrams. They depict conditions along a given latitudinal belt (from 2N to 2S) across a specific range of longitudes (this is what you find on the x-axis). Time is represented on the y-axis, with the most recent time toward the bottom. This figure presents 3 years of data recorded by ocean buoys, including zonal (i.e., west-east) wind, sea surface temperature (SST), and the depth in meters of the thermocline. The thermocline is where ocean temperatures drop off very quickly, from the relatively warm surface waters, to the cool waters of the ocean depths. In the third panel of this plot, the thermocline is equated to the depth at which ocean temperatures drop below 20C. The advantage of presenting information this way is that it allows us to see cycles in the data. For example, focus on the middle panel, the SSTs. Notice how temperatures east of 140W are generally cool—except around March, April, and May of each year. (Note: The months are depicted on the y-axis as well—just the first letter of each month!) This figure makes it easy for us to see that the eastern Pacific experiences a short period of warming every year during the Northern Hemisphere spring.
3. In examining data over a number of years, what connections do we see between sea surface temperature and precipitation anomalies?
   Show me the answer
   Hide
   Generally, temperature and precipitation anomalies are well correlated. This means that when sea surface temperatures increase (positive anomalies), we also have positive precipitation anomalies.
4. If we see anomalies in sea surface temperature, why do we also tend to see anomalies in pressure and precipitation? (Note, simply saying "they are related to each other" is not a sufficient answer. Why are they related to each other?)
   Show me the answer
   Hide
   The answer to this lies in our understanding of basic meteorology. As ocean temperature increases, that warm water heats the air just above the ocean. As the air heats, it becomes more buoyant and rises. This process creates lower atmospheric pressure at the surface. As that air rises farther, it begins to cool, and water vapor in that air condenses to form a cloud. That cloud will produce rain if enough condensation occurs. So, to summarize, warm oceans lead to lower atmospheric surface pressure, which, ultimately, can lead to the development of rainfall.
5. What regions are impacted the most by cyclic changes in temperature and precipitation in the tropical Pacific?
   Show me the answer
   Hide
   Countries and regions that are impacted the most by cyclic changes in the tropical Pacific include those in both the western and eastern Pacific: Australia, Indonesia, Oceania, and the west coast of South America, especially Ecuador and Peru.
6. Thinking back to the article you read in Unit 1, if the people of the Andes find that their view of the constellation Pleiades is obscured when they look to the west, what implications do you think this has for precipitation and temperature in the ocean just off the coast of South America? Explain your answer.
   Show me the answer
   Hide
   The fact that the Pleiades is obscured probably means that there is increased cloudiness in the eastern Pacific, off the coast of western South America. This cloudiness might be associated with warmer ocean temperatures, lower atmospheric surface pressure, and more precipitation. (See the answer to question 4 for an explanation of the connections between temperature, pressure, and precipitation.)