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SF exam > Tides & Currents > Flashcards

Tides & Currents Flashcards

1
Q

What type of tide occurs when the sun and moon are in conjunction or opposition?

A

Spring Tide

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2
Q

What type of tide occurs when the moon is in quadrature?

A

Neap Tide

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3
Q

What type of tide occurs when the moon is in apogee?

A

Apogean Tide

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4
Q

What is apogee?

A

A celestial body’s furthest point from another body during its orbit around that body.

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5
Q

What is perigee?

A

A celestial body’s closest point to another body during its orbit around that body.

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6
Q

A tidal or lunar day is _____ hours / _____minutes?

A

You could have answered with any of the following: 1. 24/50 2. 24.83

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7
Q

The national tidal epoch is ______ years?

A

You could have answered with any of the following: 1. 19

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8
Q

The nodal period is ______ years? What is it?

A

The time for the moon and sun to repeat their movement in relation to each other You could have answered with any of the following: 1. 18.6 years

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9
Q

What is the difference between two consecutive high and low waters caused by the moon’s declination?

A

Diurnal Inequality

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10
Q

How often do the the cycle of spring and neap tides repeat?

A

1/2 of the Lunar Month, Synodical Period (29 1/2 days).

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11
Q

The synodical period is _____ days?

A

You could have answered with any of the following: 1. 29 1/2 2. 29.5

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12
Q

How many days long is the orbital period (perigee to perigee) of the moon? What is it called?

A

Anomalistic Month You could have answered with any of the following: 1. 27.5 2. 27 1/2

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13
Q

What tides occur when the moon is at maximum declination?

A

Tropic Tides

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14
Q

What tide occurs when the moon is at 0 degrees declination, or on the celestial equator?

A

Equatorial Tide

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15
Q

What is the period, in days, of the moon’s declination? What is it called?

A

Tropical Month You could have answered with any of the following: 1. 27 1/3 2. 27.33

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16
Q

Define Diurnal Tides

A

One high water and one daily low water.

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17
Q

Define mixed tides

A

Large inequality between consecutive high water, low water, or both

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18
Q

Define semi-diurnal tides

A

Two high and two low waters daily with little difference between consecutive high and low waters.

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19
Q

What are the time variations that can be expected from the listed time in the tidal current tables?

A

1/2 to 1 hour

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20
Q

The fastest water in a channel is normally in the middle of a channel.

A

The correct answer is: True

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21
Q

The fastest water is generally on the outside of a turn in a narrow channel.

A

The correct answer is: True

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22
Q

The fastest water is generally on the inside of a turn.

A

The correct answer is: False

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23
Q

What is the period of no appreciable vertical rise and fall of the tide called?

A

The stand of the tide. (or Platform Tide)

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24
Q

What is a high water or consisting of two maxima of nearly the same height or two low waters with two minima of nearly the same heights with a small depression between?

A

Double Tide or Agger

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25
Q

What is it called when the high water occurs prior to the transit of the moon, due to changes in the relative position of the moon and the sun? When does this occur?

A

Priming of the Tides - Occurs between the New Moon and 1st Quarter & The Full Moon and 3rd Quarter.

26
Q

What is it called when the high water occurs after the transit of the moon, due to changes in the relative position of the moon and the sun? When does this occur?

A

Lagging of the Tides - Occurs between the 1st Quarter and The Full Moon & 3rd Quarter and New Moon.

27
Q

What effect does barometric pressure have on the height of the tide?

A

A low will raise the level and a high will decrease the level. (1 cm per hectopascal change / 13.6 inches per inch Hg change)

28
Q

An increase of in barometric pressure of 1 inch will cause a decrease in water level by approximately _________ inches?

A

You could have answered with any of the following: 1. 13.6

29
Q

A decrease of in barometric pressure of 1 hectopascal will cause an increase in water level by approximately _________ centimeter(s)?

A

You could have answered with any of the following: 1. 1 2. one

30
Q

The seasonal variation in the water level or current, cheifly due to meteorological causes.

A

Annual Inequality

31
Q

A physical object of marks as a reference for a vertical datum.

A

Bench Mark

32
Q

Something having a period or cycle of approximately one tidal day.

A

Diurnal

33
Q

Which has a greater affect on diurnal inequality. 1. the declination of the sun 2. the declination of the moon

A

The correct answer is: Number 2 the declination of the moon

34
Q

The metonic cycle is _____ years.

A

Same as the National Tidal Datum Epoch You could have answered with any of the following: 1. 19 2. nineteen

35
Q

Declinational inequality is the same as…

A

Diurnal Inequality

36
Q

The difference in height between mean higher high water and mean lower low water is…..

A

Great Diurnal Range, or diurnal range

37
Q

The astronomical occurance creating tide and the affect on the tide happen at the concurently

A

There may be a lag of several days The correct answer is: False

38
Q

For the most part, tide and current predictions of US reference stations are based on analysis of at least ___ year.

A

1 year

39
Q

Tide and current tables are published by the?

A

NOS National Ocean Service

40
Q

In the tide and current tables a table of local mean time of sunrise and sunset are given for ever _____ day

A

5th day

41
Q

In the tide and current table for moon rise and moon set is given daily from _____ different places

A

6 places

42
Q

In the tide and current book a table of the moon phases is given from what place?

A

Greenwich

43
Q

The datum for the pacific coast of the united states ( including hawaii and alaska) is the _____ of the ______ of the two low waters of each day

A
  1. Mean

2. Lower

44
Q

With onshore winds or low barometric pressure, both high and low waters will be _____ then predicted

A

higher

45
Q

With offshore winds or high barometric pressure, both high and low waters will be _______ then predicted

A

Lower

46
Q

There are seasonal variations in sea level, but these variations have been included in the tidal prediction from each station. This seasonal variation is usually less than?

A

6 inches

47
Q

Tides follow the moon more closely than the sun, and a lunar or tidal day is ______ minutes longer than a solar day

A

50 minutes

48
Q

There are usually __ high waters and ___ low waters in a day

A

1) 2

2) 2

49
Q

The _____ minute difference between a lunar day and solar day is what causes the times of tides to be ____ each day.

A
  1. 50 minutes

2. Later

50
Q

On certain days of each month at some reference stations, there will only be 1 high water and 1 low water through the lunar day. what is it called?

A

Dirunal

51
Q

The time of high water or low water does not correlate with a ______ current. It can differ from between ____ hour to _____ hours

A
  1. Slack

2. 1 to 3 hours

52
Q

What are more accurate, subordinate stations or reference stations?

A

Reference stations are more accurate because they are based on much larger periods of analysis

53
Q

The mean spring range of tide is the average _____ range occurring semimonthly as a result of the moon being new or full

A

semi diurnal

54
Q

The diurnal range is the difference in height between mean _______ water and mean ______ water

A
  1. mean higher high water

2. mean lower low water

55
Q

All elevations are provided in feet relative to __________, the reference datum on for tide predictions and soundings on NOAA nautical charts.

A

Mean Lower low water

56
Q

Coast lines are measured from __________ and shorelines are measured from _________

A
  1. mean low water

2. mean high water

57
Q

__________ tides or currents are tides or currents of decreased range or speed occurring monthly as the result of the moon being in __________

A
  1. Apogean tides or currents

2. Apogee

58
Q

The present national tidal datum epoch is taken from 19___ to 19___ and is reviewed annually for any revisions.

A

1960 to 1978

59
Q

PORTS sites (Phyisical Oceanographic Real Time Stystems) provide constant tide and current, weather and water temperature . It is call in or internet based. Where are the sites located on our region?

A
  1. Tacoma

2. Cherry Point

60
Q

Tidal predictions for the (Tacoma) Narrows have been significantly higher than predicted? T/F

A

True

61
Q

PSP have reported that tides at Neptune Beach can be up to ________ hour(s) earlier than predicted, with close to ___________ the velocity

A
  1. 1

2. double

62
Q

Freshets and droubts may change predicted values at the stations up to ___________, however the stations generally account for the seasonal change.

A

1 foot

SF exam (14 decks)

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