Learning Objectives

Through this activity, you will:

  1. Use web-based data sources to learn about ENSO, how it works, and how we measure it. This will complement material you have also learned in lecture.
  1. Learn how to use real datasets published by NOAA’s National Weather Service on ENSO to interpret historic trends in ENSO events and current conditions.
  1. Assess the current state of ENSO and interpret what this means for weather conditions in southern California and elsewhere in the U.S.

Procedure

Part A. Understanding the El Niño-Southern Oscillation (ENSO)

Go to the website https://www.climate.gov/enso. Scroll down to the tab that says “What is ENSO?”. Read through the information on this tab, and click on the link that says “What is El Niño in a nutshell?”. Read through this material and answer the following questions.

  1. What are the 3 phases of ENSO?
  2. Why is ENSO considered an ocean-atmosphere climate variability phenomenon?
  3. What are the changes in the ocean and atmosphere that occur during the El Niño phase?

Ocean:

Atmosphere:

  1. What are the changes in the ocean and atmosphere that occur during the La Niña phase?

Ocean:

Atmosphere:

  1. Why is this phenomenon named “El Niño”? Who discovered El Niño?
  2. What does the “Southern Oscillation” refer to? Who discovered it?
  3. Why did scientists combine the terms El Niño and Southern Oscillation in the acronym ENSO?

Now click on the link at the bottom of the page that says read more here. Read the article and answer the following questions.

  1. What is the Oceanic Niño Index (ONI)? How is it defined and measured? Which region of the ocean does it refer to?
  2. How is a significant ENSO ‘event’ defined using the ONI (i.e., what values define an El Niño and a La Niña)?
  1. Next, Look at the graph of the ONI over the past 20 years. When was the last El Niño event? When was the last La Niña event?

Now, to get a better sense of historical ENSO variability, go to the following website for the National Weather Service Climate Prediction Center and view the table of historic ONI values. Note that the top row in the table is a 3-month rolling average window. Just consider the values to be associated with the middle month in the sequence. For instance, for DJF, this value would be roughly associated with January of that year.

https://origin.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/

ONI_v5.php

  1. Since 1980, how many significant El Niño events have there been? How many La Niñas? What year had the biggest El Niño over this time, and what was the ONI that year? What year had the biggest La Niña, and what was the ONI that year?

Part B: ENSO “teleconnections” and effects on weather in the U.S. and southern California

Go back to https://www.climate.gov/enso and answer the following questions.

  1. What is a ‘teleconnection’ and why is ENSO considered to be this type of phenomenon?
  1. What phase of ENSO are we in now (look at the Current Status)?
  2. What are the typical weather impacts (temperature, precipitation) in Southern California based on current ENSO conditions (scroll down to “U.S. Impacts”)?
  3. Click on the 3-month outlook under “U.S. Impacts”. This spring (the next 3 months) should we expect above or below normal temperatures in Santa Barbara and by what probability (% chance)? Should we expect below or above normal precipitation and by what probability (% chance)? Do these outlooks for temperature and precipitation match up with expectations (or not) for “typical” conditions for our current ENSO phase? Explain why/not.

Now go the webpage http://www.esrl.noaa.gov/psd/enso/climaterisks/. Here you will find information about how the phase of ENSO can influence weather patterns across the United States. Play around with the interactive graphic and answer the following questions.

  1. What regions of the United States have warmer than average winter (Dec-Feb) temperatures during a La Niña? Which regions have cooler than average temperatures under La Niña conditions?
  1. Does La Niña increase of decrease the chance of precipitation for Southern California? During what time of year does the greatest effect of La Niña on Southern California precipitation occur?
  2. Southern California is currently in a drought and could use some rain. Should we be hoping for an El Niño or a La Niña event and why?