Activity: ENSO and Its Impact on Weather

WEAX 201
Module 6 Activity – ENSO and its Impact on Weather

Links needed

https://www.weather.gov/jetstream/enso

Activity Objectives:

1. Define ENSO (El Niño/Southern Oscillation).

2. Differentiate between the El Nino and La Nina phases of ENSO.

3. Describe the impacts of ENSO on weather in the United States.

Text Reference: Chapter 10 Topic Atmosphere-Ocean Interactions > El Niño, La Niña, and the Southern Oscillation

Web References: JetStream Tropical Weather – ENSO Cycle (ENSO, El Niño/La Nina, and Weather Impacts lessons)

Video from the UK Met Office El Nino – What is It? (4:26) – https://www.youtube.com/watch?v=WPA-KpldDVc ENSO, utilizing animated graphics for a visual aid in understanding the main concepts.

Introduction

The Chapter 10 topic Atmosphere-Ocean Interactions discusses the importance of the interaction between the air and the ocean on the global circulation of air and ocean water. In this activity, you will explore El Nino/Southern Oscillation and its impacts on global weather in more detail.

Activity Instructions

After reviewing the text and web references above, go to JetStream Tropical Weather – ENSO Cycle and study the information in the ENSO, El Niño/La Niña, and Weather Impacts lessons. Then, answer the following questions to check your understanding of the major concepts as outlined in the lessons:

1. Develop a one sentence summary definition of ENSO (El Niño/Southern Oscillation).

2. In the ENSO cycle, by how many degrees does the sea surface temperature typically deviate from normal within the defined Niño 3.4 monitoring region of the equatorial Pacific Ocean, and how do the deviations differ between El Niño and La Niña (hint: interpret the Ocean Temperature Departure from Normal – Niño 3.4 graph in the ENSO section)?

3. In comparison to the neutral phase of ENSO (i.e., in comparison to normal conditions), what are the conditions in the South Pacific during the El Niño phase of ENSO, in terms of the pressure patterns, relative strength and direction of the trade winds, upwelling along the west coast of South America, sea surface temperatures, and rain patterns?

4. In comparison to the neutral phase of ENSO (i.e., in comparison to normal conditions), what are the conditions in the south Pacific during the La Niña phase of ENSO, in terms of the pressure patterns, relative strength and direction of the trade winds, upwelling along the west coast of South America, sea surface temperatures, and rain patterns?

5. Changes in weather associated with ENSO are due to its effect on the jet stream. Explain, in general terms, how ENSO affects the pattern of the jet stream and how that, in turn, affects global weather patterns.

6. Summarize the changes from a normal winter (December-February) in air temperature and precipitation patterns in the United States during an El Niño phase of ENSO (hint: see the summary graphic in the Weather Impacts section – for example: the typical changes from a normal winter in air temperature and precipitation patterns in the south-central and southeast United States, during an El Niño phase of the ENSO cycle, are wetter and cooler than normal.).

7. Summarize the changes from a normal winter (December-February) in air temperature and precipitation patterns in the United States during a La Niña phase of ENSO (hint: see the summary graphic in the Weather Impacts section).

8. Summarize the change from normal in the number and intensity of tropical cyclones in the North Atlantic during a moderate to strong El Niño phase of ENSO.

Now, go to Module 6 of the course website and take the associated Quiz. Use your answers to the above questions as guidance in completing the quiz. Your score on the quiz will be your score for this activity.