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Project Summary

Difficulty	8  –  10
Time required	Long (a couple of weeks)
Prerequisites	Good computer skills
Material Availability	Readily Available
Cost	Very Low (under $20)
Safety	No issues

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Objective

The goal of this project is to study the historic relationship between the El Niño/Southern Oscillation (ENSO) and the number and strength of hurricanes, either in the Atlantic or Pacific Oceans.

Introduction

Is global warming causing an increase in hurricane intensity? Consider the following causal chain:

• Greenhouse warming is contributing to the global tropical sea surface temperature increase (still controversial).
• Global tropical sea surface temperature is increasing.
• Global hurricane intensity increases with increasing sea surface temperature.
• Global hurricane intensity is increasing.

Note: However, we are still working on this last link. The statement that "greenhouse warming is" cannot conclusively be linked to the "contributing to the global tropical sea surface temperature increase" yet. There are numerous papers just beginning to make this link, but climatologists predict that extreme events, like hurricanes, will be stronger and more frequent as the man-made climate warming increases. (For more information, see GFDL, 2006.) The timing of this increase is important. Many scientists are finding evidence that support the assertion that we are already seeing this increase in the stronger and more frequent extreme events, due to man-made causes (i.e., fossil fuel emissions.)

The story may be even more complex! Greenhouse warming may also influence hurricanes through changes in pre-existing natural cycles (e.g. El Niño), atmospheric circulation patterns, and ocean mixed layer depth. More research is needed on the global climate dynamics of hurricanes.

Multi-decadal Fluctuations in Atlantic Hurricane Activity

Historically, scientists have thought that the Atlantic hurricane activity has exhibited very strong multi-decadal variability, with alternating periods lasting several decades of generally above-normal or below-normal activity. These multi-decadal fluctuations in hurricane activity result nearly entirely from differences in the number of hurricanes and major hurricanes forming from tropical storms first named in the tropical Atlantic and Caribbean Sea.

Hurricane seasons during 1995-2004 have averaged 13.6 tropical storms, 7.8 hurricanes, 3.8 major hurricanes, and with an average Accumulated Cyclone Energy (ACE) index (NWS, 2006) of 159% of the median. NOAA classifies all but two of these ten seasons (El Niño years of 1997 and 2002) as above normal, and six of these years as hyperactive. If the 2005 season verifies as predicted, it will be the seventh hyperactive season in the last 11 years.

In contrast, during the preceding 1970-1994 period, hurricane seasons averaged 9 tropical storms, 5 hurricanes, and 1.5 major hurricanes, with an average ACE index of only 75% of the median. NOAA classifies twelve (almost one-half) of these 25 seasons as being below normal, only three as being above normal (1980, 1988, 1988), and none as being hyperactive.

What is the relationship between hurricanes and El Niño/Southern Oscillation (ENSO)? In general, warm ENSO episodes are characterized by an increased number of tropical storms and hurricanes in the eastern Pacific and a decrease in the Gulf of Mexico and the Caribbean Sea.

• Atlantic Ocean: It is believed that El Niño conditions suppress the development of tropical storms and hurricanes in the Atlantic; and that La Niña (cold conditions in the equatorial Pacific) favor hurricane formation.
• Pacific Ocean: El Niño tends to increase the numbers of tropical storms in the Pacific Ocean.

To help answer these questions NOAA has developed the Historical Hurricane Tracks tool. This interactive mapping application allows students to search and display maps using Atlantic Basin and East-Central Pacific Basin tropical cyclone data (NOAA, 2005). In this project, you will use the Historical Hurricane Tracks tool to gather information about the number and strength of past hurricane seasons. You will use this data to see if there is a correlation between ENSO and the number and/or strength of hurricanes in either the Atlantic or Pacific Oceans.

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

• hurricane-related terms:
  • eye of the storm,
  • storm surge,
  • tropical depression,
  • watch and warning information,
  • eyewall,
  • sea surface temperature,
  • Saffir-Simpson scale;
• El Niño Southern Oscillation,
• La Niña.

Questions

• How do hurricanes form?

Bibliography

• Accumulated Cyclone Energy (ACE) Index definition:
  NWS, 2006. "Climate Prediction Center, Atlantic Hurricane Outlook, Background Information," NOAA/National Weather Service [accessed June 30, 2006] http://www.cpc.ncep.noaa.gov/products/outlooks/background_information.shtml.
• CNN, 2006. "Atlantic Hurricane Season 2004," Cable News Network [accessed June 30, 2006] http://www.cnn.com/SPECIALS/2004/hurricanes/interactive/hurricane.paths/index.html.
• This site gives the data for the actually path of the hurricanes in particular states. You can choose the storm that you would like to watch and track.
  The JASON Project, 2005. "JASON Digital Lab: Hurricanes," The JASON Project [accessed June 30, 2006] http://www.jason.org/digital_labs/hurricanes/Hurricane.html.
• Good data site for info on climate profiles and locations of storms.
  NWS, 2006c. "Tropical Cyclone Climatology," NOAA/National Weather Service [accessed June 30, 2006] http://www.nhc.noaa.gov/pastprofile.shtml.
• GFDL, 2006. "Global Warming and Hurricanes, " Geophysical Fluid Dynamics Laboratory, NOAA [accessed June 30, 2006] http://www.gfdl.noaa.gov/~tk/glob_warm_hurr.html.
• McPhaden, M.J. and Soreide, N.N., date unknown. "Frequently Asked Questions About El Niño and La Niña," Pacific Marine Environmental Laboratory, NOAA [accessed June 30, 2006] http://www.pmel.noaa.gov/tao/elnino/faq.html#hurricanes.
• NOAA, 2006. "Hurricanes: Nature's Greatest Storms," NOAA [accessed June 30, 2006] http://hurricanes.noaa.gov/.
• NOAA, 2005. "Historical Hurricane Tracks," NOAA Coastal Services Center [accessed June 30, 2006] http://hurricane.csc.noaa.gov/hurricanes/viewer.html.
• NOAA, 2004. "El Niño," Science with NOAA Research [accessed June 30, 2006] http://www.oar.noaa.gov/k12/html/elnino2.html.
• NWS, 2006b. "NHC/TPC Archive of Hurricane Seasons," NOAA/National Weather Service [accessed June 30, 2006] http://www.nhc.noaa.gov/pastall.shtml.

Materials and Equipment

To do this experiment you will need the following materials and equipment:

• computer with Internet access.

Experimental Procedure

Use the Historical Hurricane Tracks tool to gather hurricane data to study the hurricane/climate connection. Here's how:

1. Open the Historical Hurricane Tracks tool (NOAA, 2005) http://hurricane.csc.noaa.gov/hurricanes/viewer.html.
2. In the Find tab, select the Query by Climatology function (see below).

3. Select the region to be studied (e.g., the "Atlantic Basin" is selected below).

4. Select a single storm category or multiple storm categories. To select a range of categories, hold down the "shift" key. To select multiple individual storm categories, hold down the control (PC) or Apple (Mac) key.
   1. Select one or more category options (Saffir-Simpson hurricane strength).

   2. If your investigation centers on the hurricane climate connection related to ENSO, you can select a checkbox for El Niño or La Niña years.

   3. Alternatively, you can select a single year (which makes isolating the hurricane tracks easier). You can make a list of El Niño and La Niña years from NOAA's "El Niño" website (NOAA, 2004). Select one or more years and, optionally, months:

5. Once you have made all of your selections, click the "Submit" button.
6. The Historical Hurricane Tracks viewer will display the tracks of the selected hurricanes.

7. Numerous tools will help view, select, and download the data.

8. To identify an individual hurricane, click on the map and zoom in to that location enough to select the track for more information.
9. Select the "Identify" button, and then click on the track of the hurricane of interest.

10. The information will be displayed below the "results" tab for the date and location you clicked. The results show the date, the hurricane name, the maximum wind speed (in nautical miles per hour, or knots), the central pressure (in millibars) and the Saffir-Simpson category.

11. The results of the hurricane track visualization can be printed or the selected data can be "extracted" for use with GIS mapping software.

12. Construct a table of hurricane data for El Niño and non-El Niño years. Do you find evidence for more hurricanes in the Pacific Basin during El Niño years? Is there evidence for greater hurricane strength? Do you find evidence for fewer hurricanes in the Atlantic Basin during El Niño years? Is there evidence for lesser hurricane strength?
13. More advanced students should test the statistical significance of the results. You can learn about how to use a t-test in the Science Buddies project Sunspot Cycles.

Variations

• Have the intensity of hurricanes increased over the last few years? (i.e. the number of Category 4 or 5 increased over the last few years?) What evidence can you construct to back up your ideas?
• Has the sea surface temperature increased over the last few years? Has this increased the number of severe hurricanes?

• For more science project ideas in this area of science, see Ocean Sciences Project Ideas.

Credits

Written by Frank Niepold, Climate Education Fellow, NOAA Climate Program Office

Edited by Andrew Olson, Ph.D., Science Buddies

Last edit date: 2006-08-15 17:13:13

Career Focus

If you like this project, you might want to think about career opportunities in Ocean Sciences.

Thousands of structures, like bridge supports, ocean oil rigs, and marine research equipment lie underwater and it is the job of commercial divers to maintain those structures. Using scuba gear, commercial divers do a wide variety of underwater tasks, including installing equipment and structures, conducting tests or experiments, rigging explosives, and photographing structures or marine life. Learn more about this career: Diver.