geography of surfing midterm 2
Terms in this set (87)
How/what is the process in which waves are created?
sun's energy heats the atmosphere -> equator is hotter at the poles -> air moves to compensate for the temp change -> vortices are produced in surface air motion -> surface air rubs on ocean -> finer waves refract near shore -> waves break on reef or beach
What is the percentage break down of coastline allocation?
20% poor exposure, cold water.
20% really good waves, daily
40% mediocore, frequency (monthly, weekly)
Is there more surf in the southern hemisphere or northern?
More surf/consistency in the southern hemisphere
What are the major regions?
Atlantic, Indian, Pacific
What are characteristics of the Northern Atlantic ocean region?
upper latitude, extreme winds, 35 mph
seas > 15 ft
30 degrees N, NE trade winds
equatorial zone doldrums
What are characteristics of the Southern Atlantic ocean region?
small surface area, no tropical storms
andres disrupt flow
Winter/Spring swells toward Africa
What are the characteristics of Indian Ocean?
Low westerlies, polar easterlies: roaring 40s
average wave height: 15'+
little seasonal variation
largest fetch anywhere on the planet
Characteristics of Northern Pacific ocean?
Upper lat: winter westerly 35mph
seas > 15 ft (Bering Sea, Aleutian Islands)
Western N. Pacific asian monsoon, E trade winds
Eastern equatorial zone: calm
Characteristics of Southern Pacific ocean?
strong westerlies 35 to 60 degrees (NZ to Cape Horn)
weaker trades than in N pacific
what is the solar energy radiation budget for reflection?
what is the solar energy radiation budget for absorption?
How much solar energy is radiated per day?
17 x 10^13 kilowatts per day
What is latitudinal variation moderated by?
Why is surface temp in the polar regions colder than the equatorial region?
Due to the more direct angle that energy traverses
What is increasing temp correlated with?
What is decreasing temp correlated with?
In regards to the hemispheric flow, where does surface air flow?
towards the equator
In regards to the hemispheric flow, where does upper atmospheric air flow?
towards the poles
In the Coriolis force, which way does air divert in the Northern hem?
to the right
In the Coriolis force, which way does air divert in the Southern hem?
to the left
what is the degree of obliquity of ecliptic???
what is the specific heat capacity in regards to land and water?
water > land
Air flows from ______ pressure to ______ pressure.
Which direction does air flow in a low pressure system?
What is the result of the Coriolis Effect?
6 spinning bands that make Hadley(?) cells..
Is cold air high or low pressure?
Where are East trade winds located? (use degrees)
What climate? and what is it influenced by?
broad claim about regions characteristics (temperature, humidity, etc)
Influenced by: elevation, topography, location
what is weather?
not consistent, comes in cycles
What is barometric pressure and what are pressure units?
weight of atmosphere above the pt
column at sea level: 14.7 lbs per sq inch
"bar" pressure of 1,000 newtons on I square m
1 bar = 1000 milibars
sea level pressure = 1013.25 mb
What is a pressure gradient and what does it act at?
Pressure gradient = (difference in pressure)/distance
acts at right angle to isobar
Winds aloft: Geostrophic
What way does wind flow in relation to isobars? What is the equation for windspeed?
Winds parallel to isobars.
Windspeed = (I/Coriolis) x (Pressure Gradient)
What are the three forces for surface winds?
PGF and CF
Surface friction (SF)
SF slow speed, reduces CF
Wind blows across isobars
How is a low pressure formation created?
air masses (warm, cold)
warm over cold..?
What are characteristics of a fully developed low?
-warm front, cold front,
-strong surface winds
-area of wind wave generation
tight isobars lead to intense low
Characterizing and describing waves: what does T represent?
period = time interval between two peaks passing a fixed point
What's the equation for the number of peaks passing a fixed point per second?
f = (I/T)
If you are measuring the time elapsed between wave peaks passing what are you measuring?
How are wind waves created..?
wind -> frictional stress -> energy
At what point does the wave reach a maximum when the rate of energy is transferred from wind to wave?
reaches maximum at the wavelength (L) corresponding to wave speed (celerity) that is 1/3 of wind speed, after that point energy transfer continues at decreasing(???) state
At 20 m/s what is the peak wave period?
At 15 m/s what is the peak wave period?
At 10 m/s what is the peak wave period?
what is the motion of water particles at the surface of water?
orbital diameter = wave height
does the diameter decrease or increase exponentially with depth?
decreases, there is zero displacement at depth
What happens when
depth < L/2
orbital pattern is flattened
what is equation for wave speed?
c = L/T
What are characteristics of deep water waves (wavelengths, periods, etc...)
Deep water waves have greatest wave lengths and longest periods, they travel the fastest and therefore are first to arrive in regions distant from the storm which generated them
what happens in radial dispersion?
Waves separate based on differing speeds
swells = energy dispersion
What percentage of the wave is lost per day of travel?
What happens as depth decreases?
Wave speed slows, height and steepness increases, but the period remains fixed
what does longer wave speed result in?
what happens with the wave energy when there is friction?
some of the energy is lost
Watching waves pass in an elapsed time is the wave ________
watching waves pass in an interval is the wave _________
To what degree does 90% of sea surface energy radiate?
30-40 degrees the angle of wind direction
what is refraction?
wave rays "turn" towards shallow water
what is concave?
refraction; if the wave rays converge energy is diffused, height decreases
what happens in diffraction?
change in direction and intensity of waves from fixed object
what is shadowing?
wave energy is blocked by islands, creates "shadows"
what are swell windows?
compass degree range that describes which directions of swell will reach a given break
What are the 3 components of wave forecasting?
energy dissipation, nonlinear interaction, and energy input from wind
wind leads to the wave energy spectra. What is the wave energy spectra?
wave period, wave height
what does the energy dissipation factor effect?
rate x time =
What should you consider before choosing where to surf?
swell windows, bathymetry, tide, local winds
In shallower water will the waves be faster or slower?
Barbarian Days: what did purists believe?
Purists thought that leashes encouraged dumb, sloppy surfing
Are waves made from onshore winds good or bad?
When cold air removes the warm air what happens (in cyclogenesis)?
the system falls apart
Where does cyclogenesis begin?
east side of rocky mountains, and in a small way on the east side of the Appalachian mountains
What's the order of Cyclogenesis?
1. stationary stage
2. Wave stage
3. Open stage
4. Occluded stage
5. Dissipation stage
This is how the weather evolves within the westerlies throughout the rest of the world
Are points on the equator spinning faster or slower than points near the poles?
Does high or low pressure air surround the "eye" of a storm (hurricane)? Why does the hurricane spin?
Low pressure is directly surrounding the center but the high pressure air surrounds the eye of the storm is constantly rushing towards the low pressure void in the middle. This air is deflected off course, causing the entire system to spin in counterclockwise position (In northern hemisphere) (in the southern hemisphere it spins clockwise)
What do isobars join together?
areas of same mean sea level air pressure
What is the rule for the southern hemisphere wind and isobars?
the 3 L's: If you Look into the wind the Low pressure system on the Left
In relation to isobars where does wind flow?
almost directly along the isobars
Because of the "spin out effect" when turning corners wind can be .....
20% higher than isobar spacing would suggest
20-40% lighter than isobar spacing would suggest
When isobars enclose an area of high pressure what is it called?
High or anticyclone. On a map it would be abbreviated with 'H'
Isobars make shapes and patterns. When they enclose an area of low pressure this is called......
Low or depressions. abbreviated with a 'L'
What does a front mark?
marks the boundary bt two air masses. appears on a weather map with triangles or semicircles
As a cold front passes, what happens?
As a cold front passes by: any rain clears but showers may appear, humidity drops, air temperature usually drops, pressure rises and the wind changes direction.
As a warm front passes, what happens?
As a warm front passes by: any rain becomes patchy but humidity remains high, air temperature may rise a little, pressure steadies, and the wind changes direction.
when does an occluded front occur?
An occluded front or occlusion occurs when a cold front overtakes a warm front, so that all that remains of the original warm air is trapped above, where it cools making dense cloud and rain.
What happens in a stationary front?
A stationary front is one which has lost its impetus for movement, so that neither air-mass is making much progress. Any rain closes slowly
What is it called when isobars make a sharp bend around a Low?
This bend area is called a trough
Where are convergence lines only drawn?
~in the tropics~