Physical Oceanography Final

Gradient Operator

Lagrangian

tag a set of particles at an initial time, and follow their paths at all future times. An ideal drifter (or patch of dye) does this. Position and velocity are expressed as functions of position at some initial time.

Eularian

at each fixed position in the ocean, express the velocity as a function of time. This is precisely what a moored current meter measures. Velocity is expressed as a function of position and time.

Net tidal forces are forces.

tractive

Define Semidiurnal and Diurnal Tides. What are mixed tides?

Diurnal - One high and low tide over 24 hours

Semidiurnal - Two High and Two low tides over 24 hours

Mixed - Somewhere inbetween

What causes semidiurnal and diurnal tides? What are the two prominent examples of locations with semidiurnal and diurnal tides.

Tidal resonance which depends on basin length and depth.

The Pacific is diurnal while the Atlantic is semidiurnal. The Atlantic is about half the width of the Pacific causing this difference.

Resonance

Forcing at the natural frequency of a system

How can you increase the resonant period?

Increase basin width and decrease basin depth.

How can you decrease the resonant period?

Decrease basin width and increase basin depth.

What are the two basic tide-generating forces?

1) Gravity

2) Centrifugal

Stable orbits require both forces to balance at Earth's center.

Gravitational force is greater on the side facing the celestial body while centrifugal force is greater on the side opposite of the celestial body.

What are the restoring forces for the following waves:

Surface Gravity Wave

Rossy Wave

Kelvin Wave

Internal Wave

Surface Gravity Wave - Gravity

Rossy Wave - gradient in background potential vorticity

Kelvin Wave - Coriolis and gravity

Internal Wave - Coriolis and gravity

Which way does the phase velocity and energy propagate for long and short Rossby Waves.

All Rossby waves phase velocity is to the West.

Short Rossby Wave's energy propagate to the East.

Long Rossby Wave's energy propagate to the West.

Are short waves non dispersive or dispersive?

What about long waves?

Short waves are dispersive

Long waves are non dispersive.

What waves are only in theory?

Coastal Kelvin Waves

Barotropic

Layers move together

Baroclinic

Layers move opposite to one another

What are Kelvin Waves? What about equatorial Kelvin Waves?

Special case internal waves when there is a vertical side wall present. Equator acts as a vertical wall as well.

What is the direction of propagation for Kelvin Waves?

Direction of propagation is with the coast on the right in the NH and left in the SH

What are the primary sources of internal gravity waves?

Wind-driven fluctuations and Tides

What is the Buoyancy Frequency/Brunt Vaisalla Frequency?

Ocean is continuously stratified which means when water parcels are displaced, they tend to oscillate. The oscillation is the buoyancy frequency.

Oscillation frequency is the product of what? What are the upper and lower limits of the oscillation frequency? How does this effect particle trajectory?

Product of N and f (Buoyancy frequency in vertical and f in horizontal)

Upper limit is N: Particle trajectory is vertical line

Lower limit is f: Particle trajectory is horizontal circle

For internal waves the vertical component of the group velocity is _ to the vertical component of the phase velocity.

opposite

Describe a general wave.

Waves carry information and energy from one place to another.

Happens when a disturbing force perturb a system and a restoring force tries to bring the system back to equilibrium.

Surface Wave vs. Body Wave

Transverse vs. Longitudinal Wave

Dispersion Relation

Show the relationship between frequency and wavenumber. Often showed as angular frequency (w)

Wave refraction

As waves approach the shore, they feel the bottom more and slow down

This causes them to become more parallel with the coastline.

Wave diffraction

Diffraction is the bending of waves around an obstacle.

When a wave is interrupted by an object creating a shadow zone

Describe the convergence and divergence zones in a propagating wave.

What type of waves are tsunami waves?

Long (shallow water) waves as they feel the bottom.

What stops/prohibits wave growth?

Wave breaking. When a wave becomes to steep (more than 1:7 in the height:wavelength ratio) the wave breaks.

What are the main components in wind wave generation?

Wind strength, wind duration, and fetch

Western Boundary Current

Currents that are warm, deep and fast flowing on the west side of ocean basins and carry water from the tropics poleward, faster than the eastern counterpart. Examples are the Kuroshio Current and the Gulf Stream.

Eastern Boundary Current

Weak, cold, diffuse, slow-moving current at the eastern boundary of an ocean (off the west coast of a continent). Examples include the Canary Current and the Humboldt Current and the California Current.

Which direction does a gradient point?

High to Low.

Cyclonic

Counter clockwise in Northern Hemisphere.

Clockwise in Southern Hemisphere.

Anti-cyclonic

Clockwise in Northern Hemisphere

Counter Clockwise in Southern Hemisphere

Latent Heat, What does evaporation and precipitation do to the latent heat in the ocean?

the heat required to convert a solid into a liquid or vapor, or a liquid into a vapor, without change of temperature. Evaporation removes latent heat from the ocean while precipitation adds latent heat.

Sensible Heat

Sensible heat is related to changes in temperature of a gas or object with no change in phase.

Higher temperature has longer/shorter wavelengths?

Higher temperature has shorter wave lengths. The sun emits shorter wavelengths than what the Earth releases.

Why does long wave and shortwave radiation matter for Earth's radiation budget?

The sun releases shortwave radiation that is absorbed by the Earth and released as longer wave radiation. This difference warms the Earth up and results in life as we know it.

Molecular Diffusion

Molecular diffusion is only effective on scales of about a centimeter or smaller, and we will ignore it in this class.

Which direction is Coriolis Force in the N. Hemisphere?

To the right.

Which direction is Coriolis Force in the S. Hemisphere?

To the left.

Which direction is Ekman Transport in the N. Hemisphere?

To the right.

Which direction is Ekman Transport in the S. Hemisphere?

To the left.

Diffusive Flux

flux due to random thermal motion of molecules

Advective Flux

flux of any fluid property (e.g., heat or salt) due to movement ofthe fluid

Radiative Flux

heat flux due to radiation of electromagnetic waves

Water is—to good approximation—incompressible. What are the implications of making this approximation?

Volume in = Volume Out. Divergence in one direction is balanced by convergence in the other.

Zonal

EAST-WEST

Meridional

North-South

What is the sign of the Coriolis parameter in the North and South Hemispheres?

Positive in North Hemisphere, negative in South hemisphere.

What is the difference between d/dt, del/delt, and D/Dt?

d/dt is the instantaneous rate of change. The standard derivative of a specific point in time. Change in BLANK over change in time.del/delt is the partial derivative in three dimensions holding either x,y, or z constant. Change in BLANk over change in time while holding x,y, or z constant.D/Dt is the total derivative following the fluid parcel.

Which direction does centrifugal force point? Centripetal? Where are these forces the greatest?

Centripetal points towards the center of rotation while centrifugal points away. These forces are felt the greatest at the equator.

Greenhouse Effect

Greenhouse gasses are longwave, and tend to be trapped in the atmosphere. Harder to escape due to longer wavelength.

Does f increase or decrease toward the equator?

Decrease

Does f increase or decrease toward the poles?

Increase

In the absence of _, if angular momentum is conserved, then potential vorticity is conserved.

Torques

What are the terms in geostrophic balance

Coriolis and pressure gradient force

If light water is on my right side in the Northern Hemisphere, my head will tilt _.

Forward

Sverdrup transport

Meridional transport of cross sections that propogate west

The beta parameter changes with _.

F

What does (+) wind stress curl mean for Ekman transport?

Divergence (upwelling)

What does (-) wind stress curl mean for Ekman transport?

Convergence (downwelling)

What does Ekman divergence mean

Stretching (Poleward motion)

What does Ekman convergence mean

Squashing (Equitorward motion)

Potential vorticity

is the relationship between f, H, and angular momentum, which must all be conserved. This is important because water tends to go along neutral densities

Geostrophic velocity goes to the of the pressure gradient force.

right (NH), left (SH)

What is the relationship between f and Ekman Transport

Ekman transport is greater with smaller f (inverse relationship) (1/f). This causes Ekman Transport to be greater at the equator.

Where does water move when it shrinks?

It moves toward the equator. Smaller H means smaller f.

What is the conservation of potential vorticity?

f * PV / H assuming PV is constant.

Where does water move when it expands?

It moves towards the pole. Larger H means larger f.

What is the result of Ekman Convergence (Upwelling/Downwelling, Shrink/Stretch)?

Downwelling and squashing.

What is the result of Ekman Divergence (Upwelling/Downwelling, Shrink/Stretch)?

Upwelling and Stretching.

What are the characteristics of North Atlantic Deep Water?

Most salty of the water masses. Forms near Greenland when winds cool down surface water. Low in nutrients and high in oxygen.