WIND AND WAVES
Learning Intention:
To understand the effects of wind on the sea.
Why do waves occur in the ocean? Thanks to Guru Cool TV for the video
Discussion:
Have you wondered where waves come from?
What is making the water move?
Waves are energy from the wind making the water go up, down and around. The faster, the further and the longer the wind blows the bigger the waves will grow.
Why are there still waves at the beach, even when it is not windy?
If the wind stops, or changes direction, the waves will stop growing, but they won’t stop travelling. Waves keep travelling away from where they were created, sometimes for days, until they run into something like a beach. So when you look at the waves breaking at the beach, those waves might be at the end of a long journey. They may have been created thousands of kilometres away, or they could have been created near you.
Oceanographers have measured waves in the Southern Ocean and have watched them travel across the Pacific Ocean all the way to the beaches of North America, more than a week later.
Storms can make enormous waves. If waves from two different storms collide they can create “freak waves”. Some have measured around 25 metres high. That would be like five giraffes standing on top of each other!
What are swells?
Swells are rolling waves that travel long distances through the ocean. They are not generated by the local wind, but by distant storms. Swells are typically smooth waves, not choppy like wind waves. A swell is measured from the crest (top) to the trough (bottom).
To measure waves like a scientist you need to understand the characteristics of a wave:
The amplitude measures the waves height from the sea level, to the crest (top) of the wave.
The wave height is measured from the trough (bottom) of the wave, to the crest.
The wavelength measures the distance from crest to crest.
The wave period is the time of one cycle from one crest to the next.
Activity: Marine reports, measure and label a wave.
Draw a wave and label the crest and trough. Measure the amplitude, height and wavelength.
Look at the Met Service Marine report for today in your area. https://www.metservice.com/marine
What does it tell you about the sea state, wind and waves?
There are several weather buoys around the coastline of New Zealand. These collect and record data about the weather, water quality and even the size of the waves. See if you can find a weather or wave buoy near to where you live.
There is a wave measuring buoy just outside Wellington's Taputeranga marine reserve. It provides wave information for shipping and forecasting. Have a look at the data here.
The Canterbury wave buoy is moored 17 kilometers east of Le Bon’s Bay, Banks Peninsula. It sends information about the waves every half hour. Check it out here.
The Port of Tauranga has a weather conditions monitoring system. This is updated every three minutes giving you wave height, wind direction and other weather information. Check it out here.
Bowentown wave buoy, on the Bay of Plenty coastline shows not only wave height, but also water temperature. View the data here.
Over a two week period choose one of the sites providing data on wave height. Record the wave height each day and compare this to what the wind was in the area at the time. What conclusions can you draw about the relationship of wind to waves?
One of the things many people love about the ocean is the waves. People love to play in the waves, surf the waves, and the sound of the waves crashing on the beach. But what are some of the dangers to watch for when we are in the waves?
Glossary:
Wind, Kōkōhau - Moving air
Ocean, Moana
Sailboat, Waka Hourua
Tāwhirimātea - The Atua or god of weather including the god of wind. He is the son of Papatūānuku (earth mother) and Ranginui (sky father)
Meteorologist - A weather scientist
Oceanographer - Someone who studies the ocean
Anemometer - An instrument for measuring wind speed
Anemometer - An instrument for measuring wind speed
Wind Vane - A device that measures the direction of the wind
Weather Prediction - What you think will happen with the weather
Sea buoy - A floating marker in the sea
Knot - One nautical mile per hour
Compass - A tool for finding direction such as North, South, East or West
Sea Breeze and Land Breeze - The winds created by a difference in temperature between the sea and the land
Prevailing Wind - The most common wind in a location
Sea State - The height of the waves
Wind Rose Diagram - A diagram that summarizes information about the wind at a particular place and over a period of time
Ocean swell, Hone - A long rolling wave that is formed a long way away
Wind Turbine, Kapohau - A propeller that gets spun by the wind to turn wind power into energy