Atsc 113


Topic 1: Clouds, Ceiling, Visibility & Fog

1a. Identify & classify clouds, and relate them to local and larger-scale weather systems and to potential hazards to aircraft

  • Clouds can be normal or special. There are two types of normal clouds. 

    • Cumuliform (connective clouds) are puffy and associated with updrafts

      • Form when humid air rises through cooler air

        • This can occur when the air at the ground is colder than the surface (ex. Air above the ocean is colder than the ocean surface)

        • Occurs behind cold fronts

        • Clear days when sunshine warms the earth more than air

        • Cold air blows over warm air or warm body of water

      • The buoyancy drives strong updrafts

      • There are 4 classifications by vertical depth:

        • Cumulus humilis (small)

          • Can have turbulence from updraft

        • Cumulus mediocris (medium)

          • Can have turbulence from updraft

        • Cumulus congestus (large)

          • Poses hazard, thunderstorms and violent updrafts

        • Cumulonimbus (thunderstorm)

          • Poses hazard, thunderstorms and violent updrafts

    • Stratiform  (layer clouds) are flatter like sheets or blanket, can extend hundreds of km’s

      • Need to rely on IFR as cannot see inside

      • Ice may form edges if cloud is below freezing

      • Form when there are layers in the atmosphere with different relative temperatures

        • Associated with warm fronts

        • High clouds approach first followed by lower and lower

      • Classified by altitude, get thicker and less holes going down

        • High

          • Cirrus: thin wispy, ice and crystals

          • Cirrostratus: thin but with more coverage: ice, halo

          • Cirrocumulus: mix, a bit lumpier

        • Middle

          • Altostratus: mix, corona

          • Altocumulus: lumpier, mix

        • Low

          • Stratus: well defined cloud base, no precip

          • Nimbostratus: blurry cloud base, some type of precipitation

1b.  Recognize and explain special clouds 





  • Unstable airloft

Small castle turrets

Atmos is unstable

Thunderstorms possible later in the day


  • Unstable airloft

Waves in a cloud

Indicate wind shear and create CAT (clear air turbulence), related to Kevin-Helmholtz waves


  • Mountain waves 

  • Strong winds across mountains

“Bubble shape” little ufo’s

Wind oscillations, may indicate mountain wind turbulence


  • Strong winds across mountains

Ragged looking under mountainClouds caused by mountains

Ragged looking cloud that forms that form at low altitude under crests of mountain waves

  • Rotors= Big hazard!!


  • Strong winds across mountains

Like a banner blowing off the mountain

Indicate strong turbulance, usually only on an isolated peak


  • Extra heat

Its over a big fire or volcano lol

Heat and moisture released so strong it can make a thudnderstorm


  • Updrafts

Like a little hat on a cumulus

Form over fast growing cumulus clouds


  • Low alt. turbulence

Ragged and low

Turbulent humid air near ground, indicate high humidity and strong winds 


  • Man made

Above smoke stacks

Water droplets condense over cooling towers


  • Man made

Trails behind airplanes

From wing-tip vortices on airplanes

1c. Relate cloud coverage amounts to the visual appearance of the sky.


Oktas (eighths of the sky covered)


Sky clear (nothing) 



Few clouds (small trails)



Scattered (large gaps)

3/8, 4/8


Broken (small gaps)

5/8, 6/8, 7/8


Overcast (no gaps)



  • Flying at altitude just above or just below a the level of clouds make them appear to have more coverage than they actually do

1d. Define the cloud ceiling, estimate its altitude, and relate it to cloud coverage amounts.

  • Clouds that cover more than half the sky create a cloud ceiling, constraints VFR pilots to fly below it and 

  • When ground visibility is very poor, referred to as vertical visibility

  • IFR pilots are still concerned with ceilings, to be able to approach airport with sufficient time to plan a landing

  • Can estimate cloud ceiling using known landmarks such as mountains, pole or tree tops

1e. Contrast horizontal visibility, vertical visibility, and runway visual range (RVR), and discuss how they affect aviation.

  • Three types of visibility and each have their own way of measuring

    • Horizontal

      • Distance you can see horizontally

      • Distance between when pilot sees a hazard and when plane hits hazard is affected by horizontal visibility

    • Vertical

      • Distance you can see vertically high or height of the cloud ceiling

  • Runway Visual Range

  • Measured at airports, how far ahead a pilot can see along a runway centerline

1f. Recognize and interpret weather and obscuration glyphs on weather charts.


1g. Explain the difference between visual & instrument flight rules (VFR, IFR) and meteorological conditions (VFC, IFC), and how they affect aviation.

  • Visual Flight Rules

    • Only flown in visual flight conditions or Visual Meteorological conditions. 

      • More than 3000 ft AGL ceiling

      • More than 5SM visibility

    • No instruments, lookout windows.

    • Hazards like fog, clouds, heavy precip

    • Marginal VFR is when it’s close call

      • Between 1000 and 3000 ft AGL ceiling

      • Between 3 and 5 SM visibility

    • VFR “over the top” is 

  • Instrumental Flight Rules

    • Conduct most of flight without looking out the window

    • Can fly in good weather and bad weather

    • Instrumental Meteorological Conditions

      • Less than 1000 ft AGL ceiling

      • Less than 3 SM visibility

1h. Anticipate when fog might occur based on location, humidity, temperature, winds, and cloud cover, and how fog affects aviation.

  • Fog is a cloud that touches the ground

    • Water droplets falling so slowly they seem suspended

    • Forms when:

      • Water is added to unsaturated air

      • Unsaturated air is cooled to its dew-point temperature

      • When ground warms the air above it!!!

  • Fog is denser and flows downhill

  • Forms in these conditions:

    • Most often late at night or early morning as cool ground cools air

      • Nights with clear skies more likely than anything else

    • Radiation: cooling at night

    • Advection: humid air blows over a cold surface (lake, snow, ocean)

    • Upslope: Upwards moving air cools against a slope (mountain, hill)

    • Precip or frontal: adding moisture, via evaporation from warm rain drops falling down through cold air below cloud

    • Steam: cold air moves over hot surface (cooling pong, warmed fields)

  • Hazards:

    • Visibility hazard

    • Can dissipate or lift

    • Hard to forecast

1i. Explain the nature of these obscurations: haze, smoke, blowing dust/sand, blowing snow, volcanic ash, rain, and how they affect aviation.



Affects aviation


Microscopic water droplets forming around a pollutant particle

Reduced visibility


Forest fires

Visibility and smoke entering cabin

Blowing dust/sand

Strong winds around deserts and sandy areas makes a…. haboob

Threat to machinery, sandblasting. Great reduction to visibility

Blowing snow

Its snow


Volcanic ash


Threat to engines, machinery of aircraft. Can melt and fuse as glass. 


Its rain

Light and moderate, reduced visibilities. Heavy rain reduces vis to point of no safety. Fly around or IFR.

Topic 2: Pressure, Temperature, Winds & Wind Shear

2a. Draw the variation of pressure & density with altitude

  • Pressure and density decrease smoothly with increase in altitude

2b. Explain how reduced oxygen at high altitude affects pilot physiology

  • Reduced atmospheric density reduces the amount of oxygen a pilot gets. 

  • At certain altitudes a pilot will get hypoxia

    • Between 12k and 15k feet: Impaired memory, thought process, reaction time, alertness, coordination. Euphoria, dizziness, drowsiness.

    • Above 15k feet: vision impaired, lips and fingers blue, unconsciousness, death

  • Solutions:

    • Above 13k, oxygen mask

    • Above 40k, pressurized oxygen

    • Above 62k, pressure suit

2c. Explain how and why pilots use “density altitude”

  • Thinner air reduces airplane performance, such as ability to take off and gain altitude

  • If low-altitude air is hot enough it can act like a lower density

  • Pilots consider density altitude before taking off

  • Depends on temperature and altitude

  • Adjusts pressure for temp.

2d. Compute crosswind & headwind components


2e. Identify the causes and typical locations of wind shear at aerodromes

  • Change of wind speed or direction with altitude

  • Almost always present near ground

  • Strong wind shear near the ground at airports make it hard to land

  • Caused by: (as well as others)

    • Caused by weather systems

    • Caused by winds flowing across mountains

    • Turbulence behinds obstacles

    • Caused by other large aircraft taking off/ landing

2f. Relate updrafts for soaring to causes including thermals, anabatic winds, and mountain waves

  • Gliders use updrafts to fly

  • The following produce updrafts:

    • Mountain waves

    • Thermals

      • Sun heats ground, warm air rises in a thermal

    • Anabatic winds

      • Warm updrafts along mountain slopes

      • Anabatic cumulus can form at top

Topic 3: Turbulence & Icing

3a. Identify atmospheric layers according to temperature characteristics in the standard atmosphere

  • Remember pressure and density decrease smoothly with increase in altitude

  • Standard atmosphere is not adjusted for local conditions, just gives average

  • Temperature does not decrease smoothly at all altitudes

  • Regions of increase and regions of decrease, which define the main layers of the atmosphere





Temp  w alt.



Almost all weather occurs here. Almost all aircraft fly here.





Constant temp the increases due to good ozone layer. Some planes fly here to avoid weather.

11-47 km







Exobase (to exosphere)

Molecules are so spread out do not act like gas.



3b. Determine the static stability given temperature soundings, and describe its effects on air motions and on aviation

  • Atmospheric stability tells weather the air will become or stay turbulent or non-turbulent (unstable / stable->(laminar))

  • Stable-> no turbulence

  • Unstable -> turbulence

  • Turbulence ranges from eddies to thermals to thunderstorms.

  • Static stability relies only on the temperature layering and not the wind

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  • If S is > 0 it is stable, =0 it is neutral, negative it is unstable

  • If multiple layers give “competing answers” (one stable one unstable) unstable always wins.

  • Unstable typically occur when it’s hot and the ground gets hot and makes all the air unstable 

3c. Describe how different types of turbulence form, and relate turbulence intensities to aircraft behavior

  • Three types of turbulence:

    • convective turbulence, or free convection, or thermal turbulence (due to buoyancy: warm air rising and cold air sinking)

    • wind-shear turbulence, or forced convection, or mechanical turbulence (different wind speeds or wind directions at different altitudes)

    • obstacle turbulence (caused by wind hitting an object and flowing around it)


Aircraft Reaction

Inside Aircraft


Slight changes 

Slight strain in seatbelts, little to no trouble walking


Changes but aircraft is in control, rapid bumps or jolts

Definite strain against seatbelts, objects are dislodged, difficulty walking


Large abrupt changes in altitude, momentarily out of control

Forced violently against seatbelts, walking is impossible, objects thrown about

3d. Describe the characteristics and causes of mountain waves, relate them to winds and stability, and describe how they affect flight

  • When air flows over a mountain in stable air (hot over cold) it can oscillate up and down creating waves in the atmosphere

  • Froude number describes the behaviour of the waves

  • When froude = 1 the waves are the most violent as the width of the mountain

  • Makes airplane go up and down “chop”. Must make corrections to remain at one altitude. Can change too fast to keep up with. 

3e. Describe the characteristics and causes of clear-air turbulence (CAT), and relate them to winds shear & stability

  • When wind shear turbulence happens outside of a thunderstorm system and nowhere near it

  • Can happen at any altitude but is strongest when winds are strongest, eg. in the jet stream

  • Cat’s are thin and flat, like a pancake in the sky, can get out by flying up or down

  • Forms when there is a wind shear across a statically stable region, interference between two layers creates Kelvin Helmholtz

3f. Compare the characteristics and causes of boundary-layer & obstacle/mountain-wake turbulence, and describe their effects on aviation

  • Boundary layer turbulence:

    • Clear air buoyant updrafts and downdrafts create wind shear interference and turbulence in the atmospheric boundary layer and planetary boundary layer

    • Weak and moderate, not hazard

  • Obstacle/mountain-wake turbulence

    • Downwind turbulence forms around larges object form with strong winds and unstable air

3g. Explain how and where supercooled water forms, and explain how ice on aircraft affects flight.

  • Water not in ice form in the atmosphere, will turn to ice as soon as it touches anything

  • Forms between 0 and -40 degrees

  • Flights from 2.5 to 8.5 km in altitude can have droplets freeze on airplane

  • Lift decreases, weight increases, drag increases, thrust decreases. They are cumulative!! One makes the others worse that makes the others worse

  • Ice breaks off and hits plane

  • On windscreen cant see

3h. Locate likely areas of turbulence, icing, and thunderstorms relative to warm, cold, occluded fronts, and dry lines, and describe how these frontal hazards affect aviation

  • Boundary between warm and cold weather is a front

  • Occluded fronts 

    • come in two flavors: cold occlusions and warm occlusions. 

    • occur when a cold front catches up to a warm front. 

    • If the advancing cold front has colder air that is retreating ahead of the warm front, then the result is a cold occlusion. Otherwise, it is a warm occlusion.

    • The resulting clouds and weather are a combination of widespread stratiform drizzle and focused intense thunderstorms. Namely, an IFR pilot could encounter dangerous thunderstorms embedded in gentle stratus clouds. Or a VFR pilot could be flying between stratiform layers and have part of the route blocked by a thunderstorm updraft tower (see figures below).

    • The warmest air between the cold and warm fronts is pushed upward above the collision between the cold and cool air, causing fronts aloft.

  • Cold fronts: 

    • winds coming from deflected around front

    • Bring thunderstorms and clear skies

    • Pointy line

  • Warm front:

    • Winds deflected around

    • Bring rain and cirrus clouds 

  • Dry lines

    • Boundary between dry and humid air of the same temperature

    • Triggers thunderstorms like cold front

  • Frontal hazards

    • Icing hazards

    • Thunderstorm hazards

    • Strong winds

    • Visibility

    • Drylines super big thunderstorm

Topic 4: Thunderstorms & Aviation Weather Services

4a. Describe thunderstorm cells, the different types of thunderstorms, and their hazards to aviation. 

  • Thunderstorms are made of cells, each like it’s own thunderstorm

    • Evolution: Cumulus -> Mature -> Dissipating -> Residue

Basic storms

Single-cell air mass

Short lived and non-violent


Two or more cells, each can be in it’s own life stage and hazards


Forms over mountains when warm air rises up slope

Mesoscale convective systems (more than one storm)

Squall line 

Wall of thunderstorms shoulder to shoulder along cold front along a cold front


A line of thunderstorms  is bent into an arc or bow shape by fast winds from behind, called the rear inflow jet (RIJ)

Mesoscale Convective Complex

This is a line or region of strong thunderstorm cells with heavy rain, followed by moderate and lighter rain extending over a broad region.

Mesoscale Convective Vortex (MCV)

If MCC dissipates late at night, remaining non-stormy clouds at middle altitudes (~5 km above ground) have a very slow rotation counterclockwise around where the center of the MCC was.

Supercells (most dangerous and longest lived, possibility of tornado)

Low-precipitation (LP) Supercell

Although LP storms do not have much rain, they can produce large hail and downburst winds.

Classic supercell

complex interplay of winds and rain, making flight near all supercells extremely dangerous. Classic supercells can have a hook-echo shape. 

High-precipitation supercell

Much more extensive rain. Rain curtains hide tornado.

4b-h. Identify thunderstorm hazards to flight & how to avoid them. 

  • Do not fly through thunderstorms, 20 nautical miles away




Convective Turbulence

Because thunderstorms are convective clouds they are driven by the buoyancy of warm air rising inside the cloud. Random fluctuations in this create turbulence. Many eddies superimposed. Don’t fly in sucker hole, lots of CAT. 

Don’t fly into thunderstorm, 20 nautical miles away. 


Strongly descending burst of air from clouds with precipitation. When they hit ground spread out as outflow winds. Leading edge is gust front. Small downbursts (in duration) are microbursts. Gust front is the front of outflow winds. Can make haboob in desert. 

Turbulence and pushing towards ground, avoid by approaching runway faster or entering holding pattern.

Lightning and P-static

Spark created in a thunderstorm, due to collisions of graupel. St.elmo’s fire is corona discharge on windscreen. No harm but can cause static on radio.

Lightning strikes very rarely damage plane. Turn up lights in cockpit to avoid blindness. Pstatic affected radio communications. 


Ice stones, path of destruction is hail swath. Hail only forms in large supercells because the upwards speed of the updraft must exceed the terminal velocity of the hailstone. 

Extremely dangerous to aircraft, can break windscreen and damage other. Can be carried out of anvil and land far away. 


Rapidly spinning air between cumulus and ground. Most come from supercells. 

Hard to predict, stay out of thunderstorms. 

Heavy rain

Rain is not hazard except for downbursts but heavy rain reduces visibility. VFR fly around except for squall line. 

Stay away

4i. Access government sources of aviation weather observations, analyses, and forecasts.

  • METAR is current observed weather at airports every hour.

  • SPECI is conditions in between METARs

  • TAF’s are forecasts of future weather. 

  • All can be encoded or in plain english.

Snow sports weather

Topic 5: Winter Weather

5a.  Interpret temperatures from pressure-level maps.

  • Pressure gives you elevation, temp contour lines give you temp. 

  • Pressure is used as analog for elevation, higher up lower pressure numbers.

5b. Interpret winds from pressure-level weather maps in terms of ski safety

  • Wind is shown with wind barbs

    • Line shows you which directions

    • More barbs the stronger the wind

    • Half barb: 10 km/h

    • Whole barb: 20 km/h 

    • Flags: 100 km/h

5c. Interpret clouds and moisture from pressure-level maps.

  • Clouds are not plotted, but relative humidity is (percent of moisture that air can hold that is currently holds) that can be used to infer clouds.

    • Less than 50%: confident there will be no clouds

    • Starts forming clouds at 70%

    • For sure overcast at 90% and above, little to no visibility. 

5d/m. Identify lows and troughs on sea level pressure maps. List weather conditions relating to low pressure that are hazardous to skiers.

  • Low pressure systems (cyclones) are associated with bad weather 

    • Heavy precipitation

    • Strong winds

    • Low visibility

  • Winds converge towards the center of a Low, since winds blow from high to low pressure. Coriolis turns air to the right that creates a cyclone. 

    • Converging air only has one place to go: up. Creates updraft which creates cumulus convective clouds. 

  • Region where pressure is lower than surrounding areas

  • Place “L”  on map where all pressure around it is increasing (completely surrounded with high pressure)

 5e/i. Use your knowledge of mean sea level pressure to identify high pressure systems and ridges on pressure maps. List the weather conditions associated with a high pressure system and their relevance to snow sports.

  • Place “H” on map where all pressure around it is decreasing (completely surrounded with low pressure) 

  • High pressure (anticyclone) is associated with good weather. 

  • Pressure differences are typically fairly weak under high pressure, so winds tend to be lighter. 

  • Typically associated with dry conditions, clearer skies, and a lack of precipitation.

  • Wear sunscreen!, occasionally strong winds. 

5f.  Identify the location of cold and warm fronts using multiple weather maps.

  • Fronts identified by lines closer together on temp maps.

  • Cold front pointy

  • Warm front circles

5g. List the weather conditions associated with cold fronts that affect snow sports.

  • Temperatures colder behind a cold front

  • Winds are strong near fronts, colds more so

  • Bring line of precipitation then scattered behind

  • Hurts visibility: Blowing snow, clouds, precip

5h. List the weather conditions associated with a warm front that affect snow sports.

  • Temperature changes can freeze/melt snow on ground or in air

  • Warm fronts bring mixed precipitation and clouds

  • Low visibility

5j.Use wind and pressure maps to predict large-scale surface high winds.

  • More barbs = more wind

  • Strong pressure gradient, more wind

5k. Use wind and pressure maps to predict ares of light/calm winds.

  • With weak pressure gradient, less wind

  • Pressure drives airflow from high to low

5n/o. Explain the limitations of different types of satellite imagery. Use satellite imagery to identify low pressure systems, fronts, and fair weather.

  • Three satellite types:

    • Visibile

      • Black and white photo from space

      • Cannot use at night

    • Infrared

      • Indicated cloud tops only not cloud depth

    • Water vapour

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Topic 6: Winter Mountain Weather

6a. Explain the causes and effects of cold air pooling

  • When there is high pressure with a stable air profile cold air pooling can occur. Mostly at night but can last into the day. 

  • Cold air just above the surface pools 

    • Hazards are very cold air in valleys and valley bottoms

    • Cold air drainage flows adding to wind chill

    • Valley cloud/ fog limits visibility

    • Freezing fog when temp within fog are below freezing

  • Plan to camp/ stay above this level

  • Strengthens inversions

  • Flows create katabatic winds

6b. Describe the diurnal evolution of slope flows

  • Happens on a daily basis, the cycle of katabatic and anabatic winds

  • Sun heats up air on slopes and it flows up in anabatic winds

    • Can form cumulus cloud over mountain top

    • Can help dissipate pools and valley fog

  • Night cools air along slopes and it flows into valleys as katabatic winds

6c. Explain what a temperature inversion is and why it is important to mountain recreation

  • When temperature increases with elevation increase in the troposphere it is known as an inversion. 

    • Occurs due to relative cooling of the ground

    • Subsidence due to high pressure

  • When an inversion is present the air is very stable as hot air is on top.

  • Because of the adiabatic lapse rate, even if the temperature decreases slowly with height, i.e. the air near the surface is very slightly warmer than air above it, it’s also considered stable, though not as stable as when there is an inversion.

    • If you don’t know can bring unexpected temperatures

    • Affects snowpack

    • Can trap moisture in the valley, then creates valley fog

6d. Identify conditions that favour valley cloud/fog formation and dissipation

  • Occurs due to:

    • Inversions

    • Cold air pooling

    • Katabatic winds

    • Downslope flow

  • Dissipates due to

    • Sunlight breaking the inversion

  • Marine clouds can move in from the ocean

6e. Explain orographic lift and lee shadowing.


6f. Identify and explain areas in the mountains that are likely to be wind-exposed.

  • Wind exposed areas are peaks and ridges of mountains, most extreme volcanoes

  • Fast winds hit mountains peaks head on

  • Friction from other peaks may slow down some winds

6g.  Identify and describe areas in the mountains that are likely to be wind-sheltered.

  • Mountain valleys, treed areas

6h/i. Determine the temperature at your elevation from pressure-level maps and adjust

  • Two step process: 

    • 1. vertically interpolate temperature from a pressure level map 

    • 2. Make adjustment to that temperature from based on heating or cooling from ground surface

  • Choose adiabatic lapse rate:

    • Dry when below 80% saturation, strong winds, daytime in spring, 

      • Decrease of 10 degrees per 1000m

    • Wet when 80% humidity or more

      • Decrease of 6 degrees per 1000m

  • Make sun heating/ cooling adjustments

    • Sun angle

    • Cloud cover

    • Wind speed

6j. Identify hot and cold conditions from observations.

  • Cold below -15 warm above 5.

  • Unseasonably warm or cold

6l. Recognize the large-scale weather pattern associated with Arctic air and outflow

  • Originates from the arctic from high pressure system

  • Very cold stable and dense.

  • “Flood” of air coming down across prairies

  • “Arctic fronts” look like cold fronts passing from eastern to western BC

6m. Describe and explain terrain channelling of winds and why this affects skiing

  • Large scale winds are altered by terrain, channelled along valleys.

  • Gap winds are when large scale wind is perpendicular to mountain range. 

  • Faster winds in smaller gaps

  • Brings colder temps, higher wind speed and changes wind sheltered areas.

Topic 7: Snow Conditions

7a. Identify and forecast the freezing level and when precipitation will fall as rain vs. snow.

  • rain-snow line is defined as the elevation at which precipitation type transitions from rain to snow

  • Not typically same as freezing level

  • To forecast rain-snow line find elevation of freezing level then subtract 300-200m

7b. Define snow density and describe what conditions will lead to high vs. low density newly-fallen snow, and why this matters to skiers.

  • Snow density is amount of mass and ice per volume 

  • High density:

    • The warmer temperature the higher the density

    • High wind speeds higher density

  • Low density:

    • Colder temperatures

    • Slower wind speeds

  • Low density is better for skiing then high density

7c. Describe right-side-up and upside-down snowfall and their significance to skiing and avalanches

  • Right-side-up snowpack

    • High density below low density

    • Good for skiing, vertical gradient lifts skiis up

  • Upside-down snowpack

    • Low density below high density

    • Hard to ski

    • More likely to have avanlanches

7d/e. Explain the factors that influence snowpack evolution. List the conditions that are favourable for rounding and faceting snow crystals.

  • Snowpack temperature gradient is the most important factor in determining the snowpack evolution

    • Faceted crystals

      • produced with a strong vertical temperature gradient.

      • Lots of space between crystals

      • More avalanche risk

    • Rounded crystals

      • When vertical temp gradient is weak

      • Tightly packed snow

7f. Describe the properties of a stable and an unstable snowpack and how to assess stability

  • Determine stability of snow by snow pit and measuring snow hardness using hand test

  • Stable has weaker layers on top of stronger layers

    • Weakly bonded layers

      • Undergone faceting

      • Surface hoars

      • New fallen low density snow

    • Strongly bonded snow layers

      • Old stellar dendrites that are now rounded crytals

      • More dense and hard with more and stronger bonds

    • Crust layers

      • Rain crust by rain on snow

      • Surface level melts then re-freezes

      • Sun crust if sun does it

7g. List characteristics and geographic regions of coastal, continental, and transitional snow climates.

  • Coastal: western side of coast in northern hemisphere. Moisture from ocean

    • Frequent snowfall with a lot of snow

    • High density

    • Warm temperatures

    • Low avanlanche danger

  • Transitional: mixture of maritime and continental snow climate, just inland from coast

    • Frequent snowfall with moderate amounts of snow

    • Moderate density

    • Lower avanlanche danger

  • Continental snow climate:  far inland away from moisture sources

    • Low snowfall

    • Low density snow

    • Persistent weak layers

    • Higher avalanche danger

7h. Describe the effects of aspect on surface snow evolution

  • The angle the sun hit the snow determines how much energy is transferred to the snow.

  • Certain sides of mountains get more sun than others

7i. Describe the atmospheric conditions for surface hoar formation and how this might lead to an avalanche

  • Formation of ice crystals on top of a snow surface

    • Clear skies

    • Calm winds

    • Strong temperature inversion

  • Can cause slab avalanches or persistent weak layers

7j. Define an avalanche, and list and describe types of avalanches.

  • Mass of snow that moves quickly down a mountain

    • Loose snow (sluff)

      • Surface or near surface snow that is not well bonded

      • Begin at single point and get more snow

      • Comprised of loose snow

      • V shape

      • Not usually very dangerous

      • Wet or dry

    • Slab avalanche

      • Layer below surface layer fails

      • Comprised of cohesive blocks

      • Wet can occur in spring

7k/l. Identify different snow crystal habits by sight. Give reasons why snow crystal habits form differently.

  • Stellar dendrites: typical snowflake

  • Columns and needles: look like name

  • Capped columns: look like I beams

  • Diamond dust: small and fun shapes

  • Graupel: little balls

  • Aggregates: like cotton candy

    • Form differently due to humidity and temperature. Temperature makes them cycle, more humidity makes them bigger.

7m/n. Describe what makes an optimal ski run for recreation and racing. List and explain ways that mountain operators reinforce the snowpack hardness on a recreational and racing ski piste

  • Optimal ski run:

    • Safe, smooth, durable, interesting, visually attractive, good grip, hard

  • To harden ski piste: Grooming machine, man made snow,water injection, chemicals

7o/p. List possible snow-surface conditions found in ski resorts and describe a possible weather scenario that leads to each condition. Give reasons why snow-surface conditions are important to ski racers and recreational skiers.

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Topic 8: Winds and Waves

8a. Describe the relationship between wind velocity, fetch, and duration, and how drag is created between the ocean and the atmosphere.

  • Three main factors in wave formation: wind velocity (speed wind blows over water), fetch (distance over water wind can blow uninterrupted) and duration (amount of time wind blows over a patch of water). Need all 3 for big waves. 

  • When wind blows across ocean it makes drag that acts against the relative motion of the two fluids. Energy from drag transferred to mechanical that makes waves.

8b. Describe the relationships between wave characteristics including shape, wavelength, period, amplitude, steepness, phase and group velocities, and wave trains. Explain how wind-generated waves, swell, rogue waves, and tsunamis are formed.

  • Steepness: ratio of wave height to wavelength

  • Wind-generated: wind disturbing surface. Restored by capillary and gravity. 

  • Swells: large waves originating from far out in the ocean

  • Rogue waves: large waves that form due to interference

  • Tsunamis: seismic events 

8c. Explain how wave characteristics determine the types of breaking waves.

  • When wave steepness exceeds 1:7 the wave will break. 

  • Spilling breakers when waves travel across sloping bottom

  • Plunging breakers: Moderate to steep bottoms

  • Surging breakers: Steep shores

8d. Explain the parameters that need to be considered when forecasting swell from distant storms.

  • Swell direction: angle at which it is coming from and how they will hit boat

  • Wave height and period

  • Local winds: can influence swell

  • Tide

  • Swell refractions: some parts of wave have more drag than other

  • Swell decay: how fast it loses energy

8e. Explain the change in wind speeds and sea state as you move along the Beaufort Wind Force Scale

  • Scale from 0-12 to describe strength of wind based on visual effects at sea or land

  • 0 is calm 12 is hurricane

Topic 9:  Large-Scale Winds 

9a. Identify the global wind circulations: Hadley cell, mid-latitude belt of cyclones, and Polar cell. Describe how the trade winds, westerlies, and easterlies are influenced by the Coriolis effect

  • Global wind circulations: Hadley cell, mid-latitude belt of cyclones, and Polar cell

  • Wind blows diff directions in northern and southern hemispheres due to coriolis effect

9b. Describe the location of the jet streams in relation to the global circulations and explain how the ridges and troughs in jet streams influence surface weather.

  • Jet streams are fast flowing, narrow bands of wind in the upper atmosphere that circle their way around the globe. The two major jet streams form where air masses of different temperatures converge. The greater the difference in temperature, the stronger the winds.  The jet stream that forms near 60° latitude is called the polar jet stream, while the one that forms at the poleward limit of the Hadley cell is called the subtropical jet stream.

  • Jet streams have a strong influence on local weather because mid-latitude cyclones (surface Lows and their fronts and bad weather) are created on the east side of jet-stream troughs (about halfway between the trough axis and the ridge). 

  • a jet-stream trough (low pressure) just west of your location is often associated with locally bad weather (clouds, precipitation, strong winds often from south-east through south-west).  But a jet-stream ridge (high pressure) just west of your location is associated with good weather (light winds from the north-west through north-east), mostly clear skies). 

9c. Describe how the trade winds influence the Walker cell and the El Niño-Southern Oscillation.

  • The longitudinal circulation across the equatorial Pacific is known as the Walker cell

  • These trade winds push the cooler water from the eastern Pacific all the way across the equator to the west Pacific, warming as it goes. The warm air over the warmer west Pacific waters rises, losing its moisture as precipitation. The dryer air then travels back towards the eastern Pacific, creating a loop. This cool Pacific air then converges with cool continental air and sinks along the eastern Pacific coast.

  • The neutral phase is the Walker cell functioning normally, while El Niño is the warmer phase of ENSO and La Niña is the cooler phase.

  • An El Niño phase occurs when the trade winds weaken

  • The La Niña phase occurs when trade winds are stronger than normal, causing increased upwelling of cool waters along the eastern Pacific and more cold water being pushed further across the Pacific.

9d. Explain the global ocean surface currents and how they are affected by wind.

  • The ocean’s surface currents are driven predominantly by frictional drag from the global winds

  • The global ocean surface currents regulate the global climate. The oceans absorb a great deal of solar energy, and surface currents help to redistribute that energy around the world. 

9e. Describe how and where hurricanes form and the influence of the Intertropical Convergence Zone and easterly waves on their formation.

  • only forms within warm tropical air masses located between the Tropic of Cancer (23.5o N) and the Tropic of Capricorn (23.5o S)

  • created by the energy or latent heat that is released as moist, warm air rises

  • he Intertropical Convergence Zone (ITCZ) occurs near the equator where the north easterly and south easterly trade winds meet. The location of the ITCZ shifts north in our summer months and south during our winter months so that it remains beneath the high sun. Because of this, large amounts of energy are available to evaporate large amounts of water, creating precipitation and thunderstorms. These storms supply the tropics with the majority of their precipitation. Sometimes, a cluster of these thunderstorms will develop into a hurricane as they build and move away from the ITCZ.

  • Easterly waves are the cause of many tropical storms, particularly those off the eastern United States. An easterly wave takes the form of a trough of low pressure. In satellite imagery, it might look like an inverted V. You will typically see fair weather on the west side of the wave and heavy rain, clouds, and thunderstorms to the east.

9f. Describe the characteristics of extratropical cyclones, sting jets, squall lines, waterspouts, and downbursts.

  • Extratropical cyclones are cyclones that form outside of the tropical or mid-latitude zones, typically between 30o and 60o latitude. can cause both mild (e.g. showers) and severe weather (e.g. thunderstorms). During the transition, the hurricane connects with other fronts or low pressure troughs.

  • Sting jets are a rare phenomenon that can be produced by specific type of extratropical cyclone in which the warm and cold fronts never meet. The sting jet forms as strong winds start to descend towards the ground, drying and evaporating as they fall, become denser and faster. strikes a relatively small area on the ground, but leaves immense devastation.

  • Squall line is a long chain of thunderstorms that forms on, or ahead of, a cold front. They form as air near the front lifts along a common lifting mechanism, such as another front or an outflow boundary. Heavy rain, thunder, lightning.

  • Waterspout is a spiralling column of air and moisture that develops over water beneath a cumuliform or cumulonimbus cloud.

9g. Describe what different weather systems (ie. High and low pressure, warm and cold fronts) look like when you’re on the water; and Describe the effects that tide and current can have on your travel speed and access to certain areas.

  • Travelling with currents and tides helps

Topic 10: Local Winds and Gusts

10a. Explain when and where you would expect to see sea and land breezes and katabatic winds.

  • Temperature differences between land and sea create sea and land breezes. During the day, both the land and the water absorb energy, or heat, from the sun; their capacity to absorb heat. The sea absorbs and releases the heat slowly, whereas the land absorbs and releases heat quickly. During a sunny afternoon, the air over the land will become warmer than the air over the sea, creating areas of low and high pressure respectively. Air moves from high to low pressure, and so the cooler air blows onshore. This is called a sea breeze.

10b. Describe how inflow and outflow winds work in a coastal inlet

  • Inflows and outflows: Local land features can create localized wind patterns. Fjords and inlets reaching from the coast to the interior act like highways carrying winds to and from coast. 

10c. Identify areas of mesoscale cellular convection (open and closed cells) and horizontal roll vortices in satellite imagery and describe how they are formed.

  • Mesoscale cellular convection occurs in the boundary layer between the Earth’s surface and the troposphere. It is most common over the oceans, where colder air from the continents blows out over the warmer ocean air. This process is known as cold-air advection. As warm air converges on the ground, it rises a few kilometers and spreads sideways. An adjacent cell does the same and the higher air spreads until they meet. The converging air between the two cells is then forced to sink. This pattern of convergence and divergence creates a honeycomb pattern of convective clouds that are recognized as open or closed cells.

  • Horizontal roll vortices, also known as cloud streets, are another product of cold-air advection and temperature inversion. They are called cloud streets because of the long rows of cumulus clouds that form due to the movement of convective currents below the inversion. Due to the force of the wind and the friction between air masses, the warm air curves as it rises, creating a roll. Warm air rises to the bottom of the inversion and forms clouds before spreading horizontally and descending back down to the water in a rolling pattern.

10d. Describe the forces that drive tidal cycles and how tides relate to currents.

  • The tide is the movement of the Earth’s oceans up and down due to the gravitational pull of the moon and sun.

  • Rising and falling of tides creates tide currents

10e. Describe the processes that drive coastal upwelling, and explain how upwelling and sea surface temperatures create fog.

  • Upwelling is the rise of cold, nutrient-rich water from the depths to the ocean’s surface. Similar to ocean currents, it is influenced by winds, the Coriolis effect, and Ekman transport

  • Sea fog is a type of advection fog, forming when warm, humid air travels over a cooler surface, in this case water. As the warm and humid summer air passes over the cold water recently risen from the deep ocean, it cools and condenses, forming fog over the water.  

10f.Recognize optical phenomena over the sea, including mirages, fata morgana, and the green flash.

  • Mirages are created when light passes through air of different densities. 

  • Fata Morgana: temperature inversion is not even

  • Green flash: during sunset green light is dispersed

11a. Determine the short-term and extended marine forecast for a given location.

11b.Relate weather warnings to wind speeds to make decisions about your sail plan. 

  • Strong Wind Warning: 20-33 kn winds

  • Gale Warning: 34-47 kn winds

  • Storm Warning: 48-63 kn winds

  • Hurricane Force Wind Warning: >64 kn winds

  • Squall Warning: gusts > 34 kn associated with a squall line, or line of storm clouds

  • Freezing Spray Warning: risk of ice formation due to low temperatures, strong winds

  • Waterspout Warning: given when a waterspout has been detected by radar or by observers