ATSC SAILING EXAM | QUESTIONS & ANSWERS (VERIFIED) | LATEST UPDATE | GRADED A+ ATSC SAILING EXAM | QUESTIONS & ANSWERS (VERIFIED) | LATEST UPDATE | GRADED A+

1 ATSC SAILING EXAM | QUESTIONS & ANSWERS (VERIFIED) | LATEST UPDATE | GRADED A+ What are the three factors that affect wave formation? Correct Answer: wind velocity, fetch, and duration what is wind velocity for wave formation Correct Answer: the speed of the wind what is fetch for wave formation Correct Answer: the distance over the water that the wind can blow uninterrupted (which can be huge distances out at sea) what is duration for wave formation Correct Answer: the amount of time the wind blows over that patch of water which is the greatest factor in wave formation? Correct Answer: wind speed, low wind speed = small waves regardless of fetch or duration 2 but need all three to create big waves how is a travelling fetch created? Correct Answer: the distance a storm can move across the ocean with prevailing winds, resulting in uninterrupted distance for storm wind to blow across upwards of 1'000 nm when wind moves across the water's surface, it creates _____. Correct Answer: frictional drag--force acting opposite to relative motion of one fluid in respect to another fluid drag forces tend to be _____ over the sea compared to on land Correct Answer: less drag from wind and the ocean's surface tends to _____ winds and _____ the oceansurface water--which makes _____ Correct Answer: slow winds; accelerate the ocean-surface water; ocean currents and waves the frictional drag felt by air is limited to _____ of the atmosphere, and is known as the ______. Correct Answer: the bottom 300m to 3km; boundary layer 3 above the boundary layers, winds are ______, and therefore ______ Correct Answer: not slowed by drag, therefore much stronger waves move ______, not water Correct Answer: energy, and the energy associated with the wave moves through the water what is the crest of a wave Correct Answer: highest point of the wave what is the trough of a wave Correct Answer: lowest point of the wave what is the wavelength of a wave Correct Answer: distance from crest to crest, or trough to trough (units = m) what is the wave height of a wave Correct Answer: height from bottom of trough to top of crest what is wave steepness of a wave Correct Answer: ratio of wave height to wavelength 4 what is the amplitude of a wave Correct Answer: distance from the centre of a wave (/rest) to the bottom of the trough (m) what its the wave period Correct Answer: time for one full wavelength to pass a given point waves typically propagate from _____ Correct Answer: the centre of a storm what is a confused sea Correct Answer: when waves from a storm combine with pre-existing waves resulting in both large and small waves of varying wavelengths moving in all directions waves moving in the _____ direction of a storm will _____ because these waves _____ Correct Answer: same direction; grow bigger; gain energy with time waves are faster with _____ wavelengths and _____ wave periods, and will _____ shorter waves Correct Answer: longer wavelengths; shorter wave periods; overtake shorter waves (faster/shorter) waves will break on distant shores first Correct Answer: faster waves will break on distant shores first 5 What is a wave train? Correct Answer: groups of waves of same wave sizes and velocities moving away from the storm/source wave energy is associated with _____ Correct Answer: a group of waves _____ waves are found at the lead and rear of a group of waves, and the ______est waves are in the middle Correct Answer: shorter waves (lead and rear); largest waves in the middle waves move through the group from _____ to _____, _______ in size then _______ when they reach the front Correct Answer: rear to the front; shrinking in size; disappearing waves form in the rear due to _____ Correct Answer: deep water dynamics what is group velocity Correct Answer: the speed at which this one group of waves travels across the water what is phase velocity Correct Answer: the apparent speed of each individual wave in the group 6 the _______ velocity is the speed at which a ______ of a wave moves across the water; typically _______ the _______ velocity Correct Answer: phase velocity; single phase; double the group The _____ of waves comes from _____, which moves with _______ not _______ Correct Answer: the destructiveness of waves comes from its energy, which moves with wave groups not wave crests wind waves are a result of... Correct Answer: wind disturbing the ocean surface and displacing water how is disturbed water restored to its calm state Correct Answer: natural forces, eg. surface tension (capillarity) or gravity Capillary waves are excited by _________ and restored by _________, and are typically ______ waves Correct Answer: excited by: small winds that displace small amounts of water restored by: capillarity/surface tension typically small waves 7 gravity waves are excited by ________ and restored by ________, and are typically _____ Correct Answer: excited by: larger winds restored by: gravity typically large waves (metres to kilometres long!) what is a swell Correct Answer: a series of gravity waves generated at a distance from heavy winds; well sorted ocean swell is typically generated by ______ and can carry ______ where it ________ Correct Answer: ocean swell is typically generated by storms out at sea and can carry energy to distant shores where it crashes as breaking waves swells with _______ wavelengths tend to have _____ wave heights and are ______ susceptible to decay from surface winds Correct Answer: longer wavelengths; lower wave heights; less susceptible what are the routes of swells known as and why? Correct Answer: Known as Great Circle routes or paths because the shortest route between two points on a sphere is a curve path 8 diamond shaped or hatched wave patterns are the result of: Correct Answer: swells meeting other swells at perpendicular angles -but could also become a confused see instead what are rogue waves and how are they formed Correct Answer: unusually large and tall waves that form due to constructive wave interference can seemingly rise out of no where what is interference? Correct Answer: when two waves run through each other to add up or cancel out what is destructive interference and what kind of waves does it produce Correct Answer: when the crest of one wave passes the trough of another wave, cancelling out -produces smaller and less energy waves what is constructive interference and what kind of waves does it produce Correct Answer: when the crest of one wave passes the crest of another wave, adding up - produces larger and higher energy waves that are temporary 9 what are tsunamis and what causes them Correct Answer: very long wavelength waves resulting from seismic activity (eg. earthquakes, underwater landslides, or volcanic eruptions) tsunami wavelengths can be _________ with ______ wave periods Correct Answer: 200km, with long wave periods tsunamis over open oceans can.... Correct Answer: travel very fast (same as jet liners) but are very small in amplitude, therefore leading to small wave slopes how does the wave height of tsunamis change when they meet continental shelves Correct Answer: start as small-amplitude, then increase dramatically forming a wall of water how does a wave change as it approaches the shore Correct Answer: wavelength is reduced the bottom of the waves drags along the ocean floor causing the front of the wave to slow down why do waves get bigger as they approach the shore 10 Correct Answer: wave height increases waves build up behind slower waves, and the wave energy gets transferred upwards why does a wave break Correct Answer: wave steepness exceeds ratio of 1:7 friction slows the bottom while the top of the wave continues forward, causing an unstable wave that breaks what is the wave steepness Correct Answer: ratio between wave height and wavelength the slope of the sea floor influences how quickly the floor affects the waves, true or false Correct Answer: true how does the direction an ocean swell approaches the shore influence the way the waves break Correct Answer: swell at an angle will cause waves reaching the shallow end to break first, then progress parallel to the shoreline to reach shallower water how does a spilling breaker occur Correct Answer: -waves travel across a gently sloping bottom 11 -breaks long and slow -energy lost through white water spilling from crest to front of wave how does a plunging breaker occur Correct Answer: -as waves approach moderate to steep bottoms -crest falls in a well-defined curl with considerable energy (surfer's favourite) how does a surging breaker occur Correct Answer: -long wave period, low amplitude waves approach moderately steep shores -builds up and slides rapidly up the beach -less foam and spray than other breakers What factors do you need to anticipate swell Correct Answer: direction swell is travelling, wave height and period, and local conditions (wind and tide) what unit is swell direction forecasted in Correct Answer: degrees; 0 degrees being north and 180 degrees being south the reported direction is where the swell _____ Correct Answer: is coming from 12 when on a boat, which swell direction would cause the most violent rolling Correct Answer: boat travelling parallel to swell; taking waves side on could capsize the boat in a sailboat which direction relative to the swell should you travel in Correct Answer: sailboat best to head into swell at an angle in which swell direction would you travel in to feel the boat 'surf' over the water Correct Answer: travelling with swell and wind behind the boat; but boat will also roll from side to side Weather buoys measure waves as they pass and provide information about _______ Correct Answer: wave height and wave period eg. swell of 6ft (wave height) at 15s (wave period) weather buoys are more representative of ________ because their reported numbers are ______ Correct Answer: representative of what you will see if on a boat; because their reported numbers are far out at sea what kind of wave characteristics do surfers want 13 Correct Answer: waves with larger wave height, or swell height, with a long period how does a longer wave period impact the wave height of waves reaching shore Correct Answer: longer wave period = more time for water to build up behind the front = more energy = higher wave strong winds on top of a swell can create _____, aka _____ Correct Answer: chop, aka a confused sea what are onshore winds and what do they produce Correct Answer: - winds that blow from ocean to shore - produces chop that reduces steepness of the wave what are offshore winds and what do they produce Correct Answer: -winds that blow from shore to ocean - winds slow the speed of approaching waves = smoother face of wave before it breaks when the tide is in/highest, swell is more likely to form what kind of breakers and why Correct Answer: high tide: spilling breakers due to gradual slope of bottom when the tide is out/low, swell is more likely to form what breakers and why Correct Answer: low tide: plunging breakers due to swell breaking further out over the steeper bottom 14 what is swell refraction Correct Answer: when one side of a swell hits shallower water sooner and the swell curves around toward that side swells with _______ wave periods will refract more than swells with _______ wave periods Correct Answer: longer wave periods refract more than shorter wave periods what does swell refraction cause Correct Answer: causes irregular breakers to form what is swell decay Correct Answer: how quickly the waves lose energy as they travel away from their initial source what factors influence rate of swell decay Correct Answer: winds, currents, other waves, shallow water, and surface tension of ocean what kind of waves will decay quickly/rapidly or slowly Correct Answer: decay quickly: steeper waves with shorter wave periods 15 decay slowly: small wave steepness with longer wave periods what is the Beaufort wind force scale used for Correct Answer: to estimate and report wind speeds based on the amount of canvas sail that a full ridged frigate (large military sailing ship) could carry scale ranges from 0-12 (12 = strongest) what is a dinghy Correct Answer: a small open cockpit sailboat, typically 2-6m used for recreation describe wind, sea condition, and dinghy sailing of Beaufort Forces 0, 1, & 2 Correct Answer: 0: wind (1 knot); sea (calm, surface smooth and mirror-like); dinghy (cannot sail, absence of wind) 1: wind (1-3 knots); sea (light air, scaly ripples, no foam); dinghy (very slow, barely sailing) 2: wind (4-6 knots); sea (breeze, small wavelets, no breaking waves); dinghy (slow sailing) describe wind, sea condition, and dinghy sailing of Beaufort Force 3 & 4 16 Correct Answer: 3: wind (7-10 knots); sea (gentle breeze, large wavelets, scattered whitecaps/beginning to break); dinghy (good dinghy sailing) 4: wind (11-16 knots); sea (moderate breeze, small waves, numerous whitecaps); dinghy (good dinghy/most dinghies get up on plane, good for larger sailing boats) describe wind, sea condition, and dinghy sailing of Beaufort Force 5 & 6 Correct Answer: 5: wind (17-21 knots); sea (fresh breeze, moderate waves, whitecaps, some spray); dinghy (advanced dinghy sailing, careful of gusts, good for large) 6: wind (22-27 knots); sea (strong breeze, larger waves, whitecaps common, more spray); dinghy (advanced dinghy and sailing, sail with reefed main sail and small jib) describe wind, sea conditions, and dinghy sailing of Beaufort Force 7 Correct Answer: 7: wind (28-33 knots); sea (near gale, sea heaps up, large waves, white foam streaks); dinghy (not suitable for dinghies, advanced sailing difficult) describe wind, sea conditions, and dinghy sailing of Beaufort Force 8 & 9 Correct Answer: 8: wind (34-40 knots); sea (gale, moderately high waves of greater length, foam blown in streaks); dinghy (very difficult to sail, head to safe haven immediately) 17 9: wind (41-47 knots); sea (strong gale, high waves, sea begins to roll, dense streaks of foam, spray reduces visibility); dinghy (dangerous, take refuge and all safety measures) describe wind, sea conditions, and dinghy sailing of Beaufort Force 10, 11 & 12 Correct Answer: 10: wind (48-55 knots); sea (storm, very high waves with overhanging crests, sea white with densely blown foam, heavy rolling, lower visibility); dinghy (extremely dangerous, inform authorities if unable to return) 11: wind (56-63 knots); sea (violent storm, exceptionally high waves, foam patches cover sea, visibility reduced); dinghy (extremely dangerous, survival mode) 12: wind (64+ knots); sea (hurricane, air filled with foam, waves over 45 ft, sea completely white with driving spray); dinghy (extremely dangerous, anchor at harbour, abandon boat for hurricane shelter) what are zonal winds and meridional winds? Correct Answer: zonal winds: winds that blow mostly in the eat-west direction meridional winds: winds that meander quite a bit to the north and south what is the intertropical convergence zone (ITCZ) or the Doldrums? Correct Answer: when warmer air near the equator rises and creates a region of heavy rain and thunderstorms 18 (because of more sunlight heating in the tropics than the poles--therefore a temperature gradient) what kind of horizontal winds can be expected in the ITCZ and what does that mean for sailing? Correct Answer: light to calm winds, difficult to sail in the ITCZ What is the movement of horizontal winds in the ICTZ like? Correct Answer: -warm air rises to troposphere -spreads out to N and S hemispheres -winds get as far as 30 degrees latitude -winds to to east and continue at this latitude what is the Coriolis effect and how does it affect wind direction in the N and S hemispheres? Correct Answer: Coriolis effect: turning motion of wind due to rotation of earth N hemi: C force pushes to the right of wind direction S hemi: C force pushes to the left of wind direction How is the subtropical high pressure zone created? How are the winds and sailing here? 19 Correct Answer: when air accumulates at 30 degrees latitude and forces some air downward toward the ocean surface--accumulation of air = subtropical high pressure zone light to calm winds, difficult to sail What are horse latitudes? Correct Answer: a belt of calm air and sea occurring in both the northern and southern hemispheres (named as such because difficult to sail in and horses used to die because of lack of movement) where deserts are favoured in both the Northern and Southern Hemispheres What are trade winds? Correct Answer: winds with a component from the east blowing toward the equator -N hemi: northeast winds -S hemi: southeast winds What is a Hadley cell? Correct Answer: a large-scale atmospheric convection cell in which air rises at the equator and sinks at medium latitudes, typically about 30° north or south. what are winds like at mid-latitudes (eg. Canada) 20 Correct Answer: not a strong vertical circulation cell winds create large horizontal eddies or waves latitude of swirling low and high pressure systems what are high pressure regions (aka anticyclones) associated with Correct Answer: fair weather, clear skies, but light light winds (not good for sailing) what are low pressure regions (aka extratropical cyclones) associated with Correct Answer: fronts, bad weather, and strong winds (not good for pleasure sailing ) which pressure system is best for sailing Correct Answer: in between highs and lows--moderate winds and OK weather what are mid-latitude Westerlies Correct Answer: a general west-east air flow, exists in both North and South hemispheres T/F: Westerlies are stronger in the Northern Hemispheres? Correct Answer: FALSE: westerlies stronger in Southern hemi because they flow mostly over water (less frictional drag) Which season are westerlies in both hemispheres stronger in? Correct Answer: westerlies stronger in winter than summer 21 where are the polar cells and how are the winds there? Correct Answer: occur between 60 degrees latitude and the poles air movements weaker than in Hadley cells (cool polar air meets warmer mid-latitude air near 60th parallel) what is the zone where polar cells occur called Correct Answer: polar front AKA polar easterlies--because winds blow from east and north, shifting east due to C effect what are jet streams and in what air conditions do they form? Correct Answer: fast flowing, narrow bands of wind in the upper atmosphere that circle their way around the globe form where air masses of different temperatures converge what are the two major jet streams called and where do they form Correct Answer: polar jet: near the 60 degrees latitude subtropical jet: forms at the poleward limit of the Hadley cell which direction do jet streams typically flow in 22 Correct Answer: flow along top of troposphere as westerly winds (however due to meandering can veer north or south) describe jet stream troughs and ridges and what season are jet streams strongest Correct Answer: troughs: jet stream meanders equatorward (area of low pressure) ridges: jet stream meanders poleward (area of high pressure) strongest in winter where are mid-latitude cyclones created in relation to jet streams? Correct Answer: mid-latitude cyclones created east side of JetStream troughs (halfway between trough axis and ridges ) what weather is associated with a JetStream trough/ridge west of your location? Correct Answer: trough to west = low at your location (bad weather) ridge to west = high at your location (good weather) What is the Walker Circulation Cell? Correct Answer: the longitudinal (east to west) circulation across the equatorial Pacific under normal conditions (also drives longitudinal air flows over Indian Ocean and equatorial Atlantic Ocean ) 23 what is the Walker cell driven by Correct Answer: driven by temperature and pressure gradients - areas of high pressure from over cooler eastern Pacific waters - areas of low pressure form over the warmer western Pacific how do near-surface winds near the equator crossing the Pacific move? Correct Answer: move from east to west as part of the trade winds how do trade winds help make air temperatures in the west warmer? Correct Answer: trade winds push some of the warm near-surface ocean water to the west describe the loop created by a Walker cell Correct Answer: - warm air over west Pacific rises, makes clouds, and loses moisture as precipitation - dryer air travels along top of troposphere towards eastern Pacific - cool Pacific air converges with cool continental air, sinks along eastern Pacific coast = loop describe an upswelling of ocean currents associated with Walker circulation Correct Answer: - warm near-surface water pushed from east-west - deeper cooler water along eastern Pacific coast rises to the surface to fill the gap 24 describe a downswelling of ocean currents associated with Walker circulation Correct Answer: - cooler water reaching surface form upswelling is blown across the Pacific and warms along the way - warm water forced to sink once it reaches Austral-Asia back to sea floor towards the east what are the three states of a Walker cell (ENSO) Correct Answer: ENSO: El-Niño-Southern Oscillation El Niño (warmer), La Niña (colder), and neutral Describe the El Niño phase Correct Answer: - occurs when trade winds weaken - warm water from western Pacific surges back towards the east - upswelling of cooler water along eastern Pacific coastline slows or stops entirely Describe the La Niña phase Correct Answer: - occurs when trade winds are stronger - causes increased upswelling of cool waters along the eastern Pacific - more cold water being pushed further across the Pacific what are the regional effect of ENSO Correct Answer: La Niña: 25 - increased fog from increased upswelling Western Canada: - not much effect of ENSO in summer - in winter: El Niño associated with warmer than average conditions, and La Niña associated with colder than average conditions - Vancouver = La Niña means wetter than average in winter (more snow) describe highs and lows in the Northern hemisphere Correct Answer: highs: winds spiral clockwise OUT of highs lows: winds spiral counterclockwise INTO lows describe highs and lows in the Southern Hemisphere Correct Answer: highs: winds spiral counterclockwise OUT of highs lows: winds spiral clockwise INTO lows what drives persistent ocean-surface currents Correct Answer: persistent climatological winds due to frictional drag between the air and the ocean, the winds exert a force on the ocean-surface water to make our planet's climate more balanced, the oceans currents... Correct Answer: ocean currents carry warm water from the equator towards the poles and cold water from the poles back towards the equator 26 what are things the ocean currents transport Correct Answer: boats, fish, plankton, chemicals, thermal energy, plastic garbage, and rubber ducks what direction of winds and currents do sailors/boats travel in Correct Answer: travel with the prevailing winds and currents--to speed up their journey what are ocean surface currents predominantly driven by? Correct Answer: Frictional drag (from global winds) Global winds including trade winds and westerlies (which are determined by the Coriolis effect and Ekman transport) Describe how the North Equatorial Current and the North Pacific Current are driven by winds Correct Answer: North Equatorial Current: north easterly trade winds push this current across the Pacific from east to west North Pacific Current: northern westerlies push this current back across the Pacific from west to east Describe how the wind-current relationship is one big positive feedback loop 27 Correct Answer: temperature of water affects the air pressure above it affects the winds drives ocean currents Describe the Coriolis effect on ocean currents Correct Answer: Northern hemi: surface currents flow slightly to the right of surface winds Southern hemi: surface currents flow slightly to the left of the surface wind When and how are gyres formed? Correct Answer: When the right (N hemi) or left (S hemi) deflection of surface currents creates clockwise (N hemi) or clockwise (S hemi) circulating ocean current What is Ekman transport? And what is Ekman spiral? Correct Answer: Ekman transport: - diminishing effect of wind on water the deeper into water you go - each layer of sewater pushed up friction of movement of the layer above it Ekman spiral: - when the drag in a water column results in a turning of the current with increasing depth - results in movement of water being 90 degrees to the right (N) or left (S) of the wind direction 28 What are the five gyres (circulating currents) in the ocean Correct Answer: North Pacific, South Pacific, North Atlantic, South Atlantic, and Indian Ocean Gyres each gyre has a strong ________ boundary current and weaker ______ boundary current Correct Answer: strong western, weaker eastern Describe the cycle of water in the North Atlantic Gyre Correct Answer: - Gulf Stream: western boundary current, brings warm water (along the eastern US) - North Atlantic Current: brings warm water from US to Iceland/N Europe - Canary Current: eastern boundary current, brings water south to northwest Africa - North Atlantic Equatorial Current: water flows back across the Atlantic, completing cycle what are the currents that make up the North Pacific Gyre Correct Answer: -North Pacific current along north -cold California current along the coast of NA -North Equatorial Current along the equator -warm Kuroshio Current along coast of Japan what are currents created by trade winds called, and how do these currents flow? 29 Correct Answer: trade winds that push ocean water towards the equator create currents call equatorial currents flow about directly along the equator without deflection what is the Coriolis effect at the equator Correct Answer: zero (0) why do you find garbage patches at the centre of an ocean gyre? Correct Answer: because waters are calm and unmoving at the centre of ocean gyres Describe currents on BC's coast Correct Answer: North Pacific current, which flows from west to east across the pacific and hits NA near BC's south coast -warm water across bottom of North Pacific Subpolar gyre and top of North Pacific Gyre - warm current reaches Americas and causes relatively mild weather at Vancouver/Southwest BC - NPC splits and turns north (Alaska current along BC's north coast and Alaska) or turns south (California current, relatively cool current) where do extratropical cyclones form Correct Answer: form outside of tropics in mid-latitude zones(30-60 degrees latitude) 30 How do extratropical cyclones move around? Correct Answer: they low centres are blown by prevailing westerlies (blowing from west to east or poleward) Winter: form every 1-4 days and are blown across the North Pacific Ocean to Canada and the North Atlantic Ocean mid latitude lows have _____ cores and _____, while hurricanes have ____ cores and _____ fronts Correct Answer: lows: cold cores, fronts hurricanes: warm cores, no fronts what is the process of new lows forming called Correct Answer: cyclogenesis what is the process of a low weakening and dying called Correct Answer: cyclolysis; lows occlude as they die (merge warm and cold fronts) Describe a large scale of weather Correct Answer: Large (planetary) scale: -weak but persistent circulation that spans a large region -represented by dashed yellow line 31 -~10'000km diameter describe a medium-large scale of weather Correct Answer: Medium-large (synoptic) scale: -typhoons and lows (small diameter, stronger winds), -high-pressure centres (weak winds, fair weather) -represented by curved black arrows -100-2'000km diameter describe a medium (mesoscale) scale of weather Correct Answer: -the width of frontal zones, particularly cold fronts -for extratropical cyclones, where the strongest winds are -represented by H or L -10-100km diameter describe a medium-small scale of weather Correct Answer: -embedded in cold fronts. typhoons, or hurricanes (eg. thunderstorms) -represented by red stars -stronger winds (horizontal and vertical) -~8-15 km in diameter describe small scale weather Correct Answer: -turbulence (incl. tornadoes and downbursts) 32 -from .01-3km diameter -extremely strong winds In BC, most of our lows come from _______ and many form over the warm waters of the ______ current in ________ Correct Answer: come from the west; form over Kuroshio current in the western Pacific Lows hitting BC reach max strength at...and occlude as they approach... Correct Answer: ...about the date line (180 degrees longitude)... ...the Gulf of Alaska and BC. what do lows hitting BC mean for the local weather? Correct Answer: widespread overcast clouds and drizzle during winter what is an atmospheric river and how does it affect local weather? Correct Answer: where lots of humid air streams rapidly toward the mountains--causes heavy rain and flooding what is a sting jet type of extratropical cyclone? And how does it form? Correct Answer: type of extratropical cyclone where the warm and cold fronts never meet forms as strong wind dry and evaporate as they descend toward the ground--which becomes denser and faster east of the low centre 33 T/F: a sting jet cyclone is not a concern to sailors Correct Answer: FALSE while striking a relatively small area on the ground, a sting jet leaves immense devastation in its wake and extremely dangerous winds for sailors what is a squall line Correct Answer: a long chain of thunderstorms that forms along, or ahead of, a cold front; produces heavy rain, thunder, and lightning T/F: squall lines are not a concern for sailors Correct Answer: FALSE major hazard (lightning, strong gusty winds, downbursts, and tornadoes/waterspouts) also advances quickly across the water what is a waterspout Correct Answer: a rotating column of air over a large body of water and under a cumuliform or cumulonimbus cloud describe the two types of waterspouts and which one is more common? Correct Answer: tornadic: -start as tornadoes on land then migrate to sea OR form from supercell tornadoes -form thunderstorm clouds downward 34 -associated with thunderstorms and bad weather -can cause severe damage to boats fair weather: -more common -begin as spiral on water's surface and work upwards to clouds in the shape of a cylinder -fast and shifting winds at bottom can capsize boat describe a downburst Correct Answer: rapidly descending column of air that hits the earth's surfaced radiates outwards; smaller (microbursts), larger (microbursts) -form during thunderstorms -cause straight line winds (very powerful, causes significant damage) what is associated with high/low pressure systems Correct Answer: high pressure -clear skies, fair weather, light-calm winds -warm, dry air descending low pressure -rain, storms, and fronts 35 -warm humid air rising and causing condensation of clouds ST1:_____ winds and ____waves found closer to ____ centres and near ____ Correct Answer: faster winds and higher waves found closer to low centres and near fronts ST2: wide band of _____ clouds associated with _____or ______ found AHEAD of ____fronts Correct Answer: wide band of stratiform clouds associated with drizzle or snow found AHEAD of warm fronts ST3: narrow band of ___ found along or just ahead of ____fronts; expect to see winds shift from _____ to ___ (in the N hem) Correct Answer: narrow band of thunderstorms found along or just ahead of cold fronts; expect to see winds shift from southwest to northwest ST4: away from fronts winds can still be ______ if there is a _____pressure gradient between H/L centres Correct Answer: away from fronts, winds can still be strong if there is a strong pressure gradient ST5: for long-distance sailing, pick a route around _____ for the ____ Correct Answer: around lows and highs for the tailwind 36 ST6: ______ pressure centres have_____winds, ____for sailing Correct Answer: high pressure centers have light-calm winds, bad for sailing The best route for long sailing trips would be to move _______ around a high, and _____around a low for a constant tailwind Correct Answer: move clockwise around a high, and counterclockwise around a low for a constant tailwind how do wind affect the waves in sailing? Correct Answer: -large winds = large waves, therefore dangerous to sail -wind travelling opposite to waves = largee choppy waves, or confused sea state global currents are ______, therefore are used for sailors travelling _____ distances Correct Answer: global currents steady and consistent; therefore used by sailors for long distances tides _____, therefore are used for sailors travelling ____ distances Correct Answer: tides more likely determine direction of currents, therefore used for sailors travelling short distances if sailing across the Atlantic, how should your route be planned? 37 Correct Answer: GOOD: ride Gulf Stream up to North Atlantic Current and end up in Western Europe BAD: straight across to N Africa, fighting the North Atlantic Equatorial Current and the trade winds what is a sea breeze? and what are similar flows? Correct Answer: -shallow cool wind blowing onshore during daytime -occurs in large-scale high pressure regions, of weak/calm synoptic scale wind, under mostly clear skies lake breezes: form along lake shorelines inland sea breezes: form along boundaries between adjacent land regions with different land-use characteristics what is the primary cause of a sea breeze? Correct Answer: a 5°C or greater temperature difference between the sun-heated warm land cooler water and a weak return flow from land to sea why does the ocean warm more slowly than the land 38 Correct Answer: because sunlight is absorbed and spread over several metres of ocean depth what is a sea breeze front and what kind of clouds can form along the front? Correct Answer: the leading edge of the advancing cool marine air over land (similar to a weak advancing cold front or thunderstorm gust front) -cumulus clouds (and turn into thunderstorm clouds) if there is enough humidity -Kelvin-Helmholtz waves (b/w the cool onshore sea breeze and the warm return flow aloft) How far can sea breeze fronts advance/travel? Correct Answer: 10-200km inland, but typically advance 20-60km unless inhibited by mountains or opposing synoptic scale winds; can also turn away due to Coriolis effect what and where does a thermal internal boundary layer form Correct Answer: where: just above ground where cool marine air flows over the land what: region of warmed air that grows in depth with increasing distance from the shores as the marine air is heated by the underlying warm ground how does a sea-breeze circulation change throughout a day Correct Answer: -spreads out further over land and over water as the day progresses 39 -at full development, inflow portion of near-surface wind speeds at the coast range form 4-40km/h (typically ~22km/h) what forms in response to the weakening of a sea-breeze circulation at night? Correct Answer: reverse circulation called a land-breeze forms -due to nighttime infrared cooling of the land surface relative to the sea -sea breeze can die late evening before the sun sets what type of wind is associated with a land breezes Correct Answer: low altitude winds flow from land toward ocean return flow aloft from ocean toward land At a normal coastline, how does the surface wind behave throughout the day Correct Answer: surface wind oscillates back and forth between onshore (coming from sea as sea breeze) and offshore (coming from land as a land breeze) sea breeze wind and the mean synoptic-scale surface wind are additive what causes the horizontal wind direction to rotate throughout the course of the day? Correct Answer: the Coriolis effect (clockwise in N hem, counterclockwise in S hem) what its the ideal hodograph of a sea breeze circulation Correct Answer: elliptical shape: 40 -strongest land breeze at 3am -strongest sea breeze at 3pm at what time of the day is sea breeze strongest Correct Answer: strongest during clear sunny daytimes under high pressure (strongest at midday though mid-afternoon) T/F: in synoptic high pressure regions, you can still get enough sea breeze near the coastline for good sailing Correct Answer: True! Despite the light to calm winds associated with high pressure regions, there is still enough sea breeze near the coast for sailing an area/band ~10-50km wide depending on local conditions what are concerns when sailing in sea-breeze bands near the coastline? Correct Answer: beware of shallow waters and rocks close to shore and beware of sailing outside of the sea-breeze band modern can travel in almost any direction relative to the wind except for... Correct Answer: cannot head directly into the wind what geographical structures can a sea breeze interact with/be distorted by? 41 Correct Answer: bays, mountains, boundary-layer thermals, urban circulations, and too strong onshore synoptic scale wind If major mountain ranges were to lie close (within a few hundred km) to the coast, what appears alongside sea breezes? Correct Answer: close major mountain ranges near coastlines = sea breezes and terraininduced winds (eg. katabatibc winds) what are katabatibc winds and how are they formed Correct Answer: cross valley flows that merge into the along Vally mountain winds down the valley; relatively warm air exists in the thermal belt/top of valley regions form from surface air cooling upon touching cold mountain slopes, becoming denser, and sinking due to gravity/buoyancy -typically form during nighttime cooling of mountains, or over bodies of ice/snow on mountains how do katabatic winds (cold downslope winds) affect the coastlines? Correct Answer: -cold wind blowing offshore -pool and become stagnant in fjords (pollution or ice fog) -flow down sloped valleys and gush out of valley mouths over coastal waters in narrow regions (become outflow winds) 42 how can sailors best avoid katabatibc/terrain-induced winds? Correct Answer: avoid sailing at night dangerously close to shore what is a coastal-trapped low-level (barrier) jet Correct Answer: when a low with a cold front hits a barrier when reaching land: -creates a shallow layer of cold air trapped against the wind-ward side of the barrier -leaves a low to high pressure gradient parallel to the barrier and fast-moving cold air from south to north what is dangerous with coastal trapped low level jets? Correct Answer: can be associated with clouds and rain, or fog and low stratus clouds how can coastally trapped low level barrier jets be good for sailing Correct Answer: if travelling north, will have a brisk tailwind = faster sailing what is an outflow/inflow? Correct Answer: outflow: when air flows out from the mountains via fjords and valleys toward the water inflow: when air from the water is flowing into the the inlets, fjords, and valleys describe outflow/inflows during summer 43 Correct Answer: -daytime solar heating creates sea-breezes and anabatic winds that flow as an inflow (water to land) -nighttime radiative cooling creates katabatibc winds that combine with land breezes that channel cold outflows Summer inflows typically occur in _______ because... Correct Answer: typically occur in spring in summer when summer weather creates higher temperatures in the interior than on the coast which is stronger, summer inflows or summer outflows? Correct Answer: summer outflows can be stronger and hazardous summer inflows are usually not strong the inflow and outflow winds are often named by local towns in the valley or fjord ________ where they wind first passes over the water Correct Answer: FROM eg. Howe Sound (fjord) sees outflow winds called Squamish winds (because the winds come from over the town of Squamish) how do synoptic winds influence the strength of local inflows and outflows in summer? Correct Answer: -often a high pressure and weak synoptic-scale winds over BC -if blowing from the south, can build the strength of afternoon inflows 44 -if blowing from the north/northwest, can diminish inflow and strengthen outflow What is the Qualicum wind on Vancouver island Correct Answer: -when high pressure ridge forms on the west side of Vancouver Island -southwesterly inflow funnels through Port Alberni Inlet -moves across the island through a gap in the mountains -emerging as strong westerly outflow winds off Qualicum beach and into the Strait of Georgia Sailors should also be aware of inlet mouths because... Correct Answer: outflow winds can come down the inlet. creating strong wind and rough seas at the mouth (despite calm and quiet seas further along the coast) describe outflow/inflows during the winter Correct Answer: -cold arctic air masses moving in create strong high pressures east of the coast range mountains and lower pressure seen on the west of coast range mountains -pressure difference pushes interior BC air out to the coastline as strong winter outflow winds winter outflows typically have a ______ pressure and _____ over central BC, but _____ air and ______ pressure just off the coast; resulting in a pressure gradient of _____ to ______ from land to ocean 45 Correct Answer: -a strong high pressure; and a cold Arctic airmass -but warmer air; and lower pressure -pressure gradient of high to low from land to ocean what acts like a dam to trap cold air in the interior of BC? Correct Answer: the Coast Range Mountains along the coastline act as a dam, except where there are valleys and fjords list outflow winds in BC Correct Answer: -howe sound into the Georgia Strait -lower Fraser valley towards the Gulf islands and towards Washington state (incl. San Juan islands) Where is a mesoscale cellular convection most likely to occur Correct Answer: in the boundary layer between the Earth's surface and the troposphere; most common over oceans behind cold fronts what is cold air advection Correct Answer: when colder air from the continents blows out over the warmer ocean air describe the pattern of convergence and divergence to create honeycomb patterns of convective clouds 46 Correct Answer: -warm air converges on ground and rises due to buoyancy before hitting a temperature inversion and spreading sideways -adjacent cell does the same and air aloft spread until it hits the air spreading form adjacent cells -converging air aloft between two cells is forced to sink back toward the surface what are open-cell convective clouds Correct Answer: -clear centres with surrounding clouds -in honeycomb pattern or adjacent hexagons of cloud rings what are closed-cell convective clouds Correct Answer: - convective clouds in the centre surrounded by clear sky how big are open- or closed-cell convective clouds? Correct Answer: diameters of 10-50 km (a size called a mesoscale), depths of 1-2km how do you identify honeycomb convective clouds on satellite imagery? Correct Answer: -trail behind cold fronts -honeycomb pattern Under what conditions do horizontal roll vortices happen most often Correct Answer: 1. when synoptic scale winds are light to moderate 2. the earth's surface (or ocean surface) is warmer than the air 47 3. cold air is advecting under a strong temperature inversion How do you identify horizontal roll vortices in the atmosphere Correct Answer: often invisible unless clouds are present; the gentle roll vortices sweep rising thermals and cumulus clouds into cloud streets (clouds streets will be roughly parallel to the wind direction, with a typical vertical thickness of 1-2 km and pair width 3x the vortex depth) what is the tide? and what is the tidal range? Correct Answer: tide: the movement of the ocean surface up and down due to the gravitational pull of the moon and sun tidal range: the difference between the highest and lowest tide in an area what causes variation in tides? Correct Answer: gravitational pull depends on positions of moon and sun (closer the moon, greater the pull on the ocean) Note: as water rises/bulges in one area, the water level decreases elsewhere (low tide seen on opposite side of earth to high tide) which type of tide is associated with each of the different moon phases? 48 Correct Answer: spring tides (forces add up, higher and lower tides than normal) = moon and sun aligned; new moon (dark moon) & full moon (bright moon) neap tides (exert opposing forces, weaker tides/tidal range) = moon and sun at right angles to each other (quarter moons) spring tides and neap tides occur ~twice a month how far into the future can tidal forecasts be generated for? Correct Answer: strength and timing of tides can be predicted up to a year in advance (countries publish annual tide tables) how many low tides and high tides do you see in a day? Correct Answer: 2 high tides and low tides each how are flood currents created and why are they known as such Correct Answer: flood currents are currents created by the rising and falling of the tides known as flood currents for the incoming tide and ebb currents for the outgoing tide with which tide do sailors want to depart in? Correct Answer: ebbing tides, because the water is travelling out/away from land what is a slack tide and explain the two types 49 Correct Answer: slack tide: when the current ceases and changes direction; a moment of no current can have high slack (tide reaches max height) or low slack (tide reaches lowest height) peak currents are therefore at the midpoint between high and low tide if you found yourself travelling against the current what should you do and why? Correct Answer: tray to navigate through waters where the current isn't as strong because currents are usually greater in the mid-channel or deepest part of the channel and weaker over water when the wind and current are travelling____ the seas are ______ than when they are opposing each other Correct Answer: wind and current travelling together, the seas are calmer why should sailors be cautious when going out in calm waters? Correct Answer: because the turn of the tide can cause relatively flat but windy channel to build into rolling waves and whitecaps (big waves out of nowhere) when are tidal rapids created and what do they consist of? Correct Answer: when fast-flowing tidal waters are forced to pass through narrow channels 50 consist of: standing water, large back eddies, intimidating whirlpools when is high slack and low slack? Correct Answer: high slack: a period of zero current which happens at high tide before it ebbs (stop between switching from flooding to ebbing) low slack: a period of zero current which happens at low tide when the tide switches from ebbing to flooding what is upwelling and what is it influenced by? Correct Answer: upwelling: the rise of cold, nutrient rich water form the deep ocean to the surface influenced by winds (wind drag), Coriolis effect, and Ekman transport (deflects direction to 90 degrees to the right (N) or left (S) of the wind) what kind of upwelling will we see on the west coast of Canada with winds from the north? Correct Answer: see an upwelling of cold water on the west coast of Canada with a wind from the north (similar upwellings along west coast of other continents) how can an upwelling affect local weather and climate? Correct Answer: cold water form upwelling can increase likelihood of fog 51 How does sea fog form and what type of fog is a sea fog? Correct Answer: type: advection fog (warm, humid air travels over cooler surface) formed when warm, humid air cools beyond dew point and condenses into water droplets in the air what are the four fogs encountered at sea, and which is the main one? Correct Answer: 1. advection fog (main) 2. radiation fog 3. frontal fog (aka precipitation fog) 4. Arctic sea smoke (aka steam fog) how and when does radiation fog form? Correct Answer: how: develops over land during night as cold ground cools warm humid air above it when: NOT windy (moderate winds), clear nights, sometimes in coastal valleys how and when does frontal fog form? Correct Answer: how: warm air rises over colder air, as warm rain falls/evaporates through cooler air 52 when: forms at most fronts (warm rising over cold); appears as a low-lying cloud how and when does Arctic sea smoke/steam fog form? Correct Answer: how: cold air blows over warm water and strong evaporation from warm water into the air (as cold air is heated by the warm sea, warm air rises into thermals) when: fleeting, disappears when the bottom hundred meters has been warmed by the ocean; resembles wisps of smoke which type of fog is most/least hazardous to sailors and why? Correct Answer: most hazardous: advection fog (day or night throughout entire year, enhanced/lengthened by coastal upwelling) least hazardous: Arctic sea smoke/steam fog (wisps of smoke, fleeting) what are factors in fog dissipation Correct Answer: - daytime: sunlight warms air - summer: sun higher in sky, faster fog dissipation than winter - faster/increasing winds: mix warm-dry with cold-humid air - light winds blow fog away/toward you - human activities: turbulent air mixing or heat being added from human things (cities, roads, fires, jet engines) 53 what are 2 ways fog can dissipate? Correct Answer: 1. become less dense = greater visibility or hazy air 2. lift off water = becomes low cloud What measures can be taken to navigate through fog safely? Correct Answer: - radar reflector - GPS to monitor location - air horn to announce location (aka fog horn) - move slowly, communicate via VHF radio - prepare for rapid changes to avoid things - use radar -get rid of background noise how is a mirage created? Correct Answer: when light passes through air of different temperatures Explain the different types of mirages Correct Answer: inferior mirage: -dense layer of cold air above line of sight, warm air below line of sight -hot summer days where hot ground heats air -rays of light from sky get refracted/bent upwards by hot air near ground -typical oasis in desert mirage -doesnt last long if layers mix 54 -less frequent over ocean (can happen if cold arctic air blows over unfrozen water) superior mirage: -warm air above line of sight with cool layer beneath it (aka temperature inversion) -light bends downwards to the denser air -object appears higher than it actually is -can act like a lens making objects smaller/larger, or closer/further away what is a Fata Morgana caused by? Correct Answer: several layers of warm and cold air that cause a combination of superior and inferior mirages creates multiple segmented reflections of the original (less recognizable than mirages; floating walls or castles) what is a "green flash" optical illusion? Correct Answer: -rare, only lasts a few seconds after sunset or before sunrise -at the horizon, sun's rays travel through more of the Earth's atmosphere, which acts as a prism splitting white light -shorter wavelengths (green, blue, violet) the last to set below the horizon -amplified by mirages (made wider) -seen on Carribean islands a few times a year 55 what are marine weather forecast resources sailors can access? Correct Answer: -environment and climate change Canada -continuous marine broadcast (updated throughout day) -weather radio (VHF weather radio channels on water) what is freezing spray Correct Answer: when breaking ocean waves make lots of sea spray (airborne droplets), and when the air is very cold, the droplets freeze almost instantly when they hit a ship (fresh water sea spray freezes at 0, salt-water spray freezes at -2) list the synoptic marine warnings (speeds and hazards) Correct Answer: -strong wind warning: 20-33 knot winds. only issued for coastal or inland waters during the recreational boating season -gale warning: 34-47 knot winds -storm warning: 48-63 knot winds -hurricane force wind warning: 64 know winds -freezing spray warning: risk of ice formation on vessels due to low temperatures and strong winds list localized marine warnings Correct Answer: -tornado warning: over the water, regardless of whether it first formed over land or water -squall warning: gusts 34 knot associated with a squall line, or line of storm clouds 56 -high water-level warning: issued only for Ontario and Atlantic regions -special marine warning: other hazards -waterspout warning: given when a water spout has been detected by radar or by observers list advance notice of localized marine watches Correct Answer: -tornado watch: for possible tornado forming later in the day -squall watch: for possible squalls forming later in the day -waterspout watch: for cold-air waterspouts forming later in the day -special marine watch: for other potential hazards what does a trough of warm air aloft (TROWAL) look like on a NOAA Ocean prediction weather map? Correct Answer: series of check marks, Canadian symbol for a type of occluded front describe the two sources of real time satellite images Correct Answer: geostationary satellites (GOES) - parked over equator at fixed longitude -advantage: good for time lapse photos to view on loop -disadvantage: far away from Canada, only get oblique view polar orbiting satellites (POES) - go from north to south poles to take image of slice of earth 57 -advantage: excellent vertical view -disadvantage: one global image per day, each slice 100 mineralizer or later than neighbouring slices.