G 351 U Oceanography Wave Characteristics Questionnaire

G 351 U Oceanography Wave Characteristics Questionnaire
PLEASE READ: Create a separate word document for your answers. Do not include the questions on your answer sheet. Just include the question number and the answer.
PART A
Wave Characteristics
Goal: The purpose of this exercise is to practice calculating wave characteristics.
Figure 1
1) In Figure 1, what is the wave height (H) and wavelength (L), in meters?
2) Describe how you could determine the wave period.
3) Calculate the wave steepness (H/L).
4) Would this theoretical wave break in the open deep ocean far from land, why or why not?
5) Imagine this wave is stable enough to approach shore. What would happen to the wave height and wavelength at very shallow water depths? Be specific.
PART B Ocean Tides & Sea-level Variation
Goal: The purpose of this exercise is to help you read tide charts, and understand tides & the forces that generate them.
Figure 2
Predicted sea level variations for a monitoring station at the waterfront in Tacoma are shown in the graph above (Figure 2). NOTE: “MLLW” = “Mean Lower Low Water Level,” which is given as a height of 0.0 ft in order to use as a point of reference. [Source = http://tidesandcurrents.noaa.gov]
6) Looking at the water level, exactly how many high tides and how many low tides are there in each day? – Be precise and notice the date & time as given on the x-axis.
7) What is the maximum height of the tide in Figure 2 (relative to MLLW) and what date & time does it occur?
8) At 10 AM on Nov. 9th, is the tide rising, falling, or neither? Does this produce a flood, ebb, or slack current?
Using Data
Now, we are going to examine some tide predictions for Astoria, OR. First, find Astoria, OR on a map (or Google Earth). Now, go to tidesandcurrents.noaa.gov/ and find the tide predictions for Astoria.
Specific instructions:
1. Go to this url: https://tidesandcurrents.noaa.gov/
2. type “Astoria, OR” into the search bar at the top right of the page.
3. Select the Astoria station (9439040 Astoria, OR)
4. Click the “Tides/Water Levels” tab and select “NOAA Tide Predictions”
(If you want to see the actual water level in comparison to the prediction, click on “Water Levels”)
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5. To see a prediction for a future (or past) date, look below the tide chart, change the date range, and click the “Plot Daily” tab.
6. You can also change other factors here. We want to see the tidal variation relative to mean sea level instead of relative to “Lower Low Water Level”, so click the “Datum” tab and choose “MSL” (Mean Sea Level).
QUESTIONS:
9) You want to go on a low tide beach walk to look at sea life on Saturday, June 2, 2018. At what time will the lowest tide of the day occur and what is the predicted tidal height relative to Mean Sea Level (MSL)?
G 351 U Oceanography Wave Characteristics Questionnaire
10) Your friends are going to take a canoe out on Sunday, June 3 and have asked you for help figuring out the general tide. They are planning to leave at 1pm from the waterfront near the HWY101 bridge and return by 4pm. They would like to plan to start paddling against the tidal current, and then “ride the tide” on the way home.
What will be the likely dominant current type during this time and what direction will the current flow towards? What direction (east or west) should your friends travel towards when leaving Astoria?
Use your lecture notes and textbook to answer the following questions.
11) In your own words, what causes the tides? Be complete in your answer.
12) The sun is much more massive than the moon, why does the moon have more of an effect on the tides?
13) What is the relative position of the sun and the moon during the two “spring tides” in the tidal cycle.
14) What is the relative position of the sun and the moon during the two “neap tides” in the tidal cycle.
15) On June 20, 2018, the moon will be in first-quarter phase (waxing). What kind of effect does this have on the tides? Does it produce neap or spring tides? Why?
16) What is the difference between diurnal, semidiurnal, and mixed semidiurnal tide cycles? You may need to remind yourself of what these are by looking at the lecture (or Figure 9.16 on pg. 279 in your textbook).
17) What type of tidal cycle is found at Astoria (diurnal, semidiurnal, or mixed semidiurnal)? Explain your answer, and make sure to check that you are looking at the tidal variation in one 24-hr day.
NOW, you are going to look at tide charts from other locations. To do this, use the NOAA tide website from above, but type in a new city in the search bar. You will have to re-select “Tide/Water Levels” ? “NOAA Tide Predictions” from the dropdown menu and “MSL” under Datum for each city.
18) What type of tidal cycle is found in San Diego, California? What is the range of tidal height given, from the lowest to the highest tide (use most recent given over the last 2 days)? Be sure to show your units.
19) What type of tidal cycle is found in Pensacola, Florida? What is the range of tidal height?
20) What type of tidal cycle is found in Eastport, Maine? What is the range of tidal height?