ATSC113 CRIB Sheet - To help you study or use during the ATSC 113 exam. PDF

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Summary

Flying: VFR =Visual Flight Rules = fly by mostly looking out the window. You need good visibility and need to stay out of clouds | IFR = Instrument Flight Rules: Navigate using GPS, instruments, relying on air traffic control (ATC), requires a filed flight plan | billow (K-H Wave) = indicate CAT and...

Description

Flying: VFR =Visual Flight Rules = fly by mostly looking out the window. You need good visibility and need to stay out of clouds | IFR = Instrument Flight Rules: Navigate using GPS, instruments, relying on air traffic control (ATC), requires a filed flight plan | billow (K-H Wave) = indicate CAT and wind shear, look like waves �|Castellanus= castle turret like clouds, these & KH wave are a sign of unstable air |Rotor Clouds = Indicate extreme and severe turbulence at low altitudes due to mountain waves (break wings, danger high, look like a UFO dome) | Lenticular clouds= vertical wave wind oscillation & possible mountain wake turbulence, bumpy ride for commercial aircrafts | Banner cloud= Form on downwind side of mountain peak. Indicate strong turbulence touching the downwind side of a tall, isolated mountain peak.| Pyrocumlus – form over forest fires and volcanoes| Pileus – fast growing cumulus, harmless.| Fractus - turbulent humid air near the ground, indicate high humidity | Human made clouds = Fumulus (towers) & Contrails | Four ways cloud ceilings are measured: Laser ceilometers, ceiling balloons, pilot reports, weather-observer estimates | METAR=Meteorological Aviation Reports | Higher altitude=pressure and density smoothly decreases |Hypoxic = goofiness from insufficient oxygen supply | Armstrong limit= altitude above which bodily fluids boil at normal body temperature. Above 62,000 ft / 19km| Density(ρ) = mass/Volume| Pressure altitude= altitude measured from atmospheric pressure alone | Density altitude= altitude that the aircraft “feels” | Crosswinds = winds coming from the sides | Headwinds = winds coming directly towards you, slowing you down | Tailwinds = winds directly behind you | Wind Components are calculated by using the components of headwind/crosswinds (see chart on next page)| Wind Shear= A change of wind speed and or wind direction with altitude | Sea breeze= colder air blowing onshore from the sea, typically during the day, Land breeze= night | Anabatic winds= warm air moving up along mountain slopes that are warmed by the sun during daytime. Can form anabatic cumulus clouds | Katabatic winds= cold air draining down mountain slopes into valleys at nighttime as the mountain slopes cools. | Mountain wave= air oscillating up and down after it hits a mountain. Downdrafts are stronger than updrafts on the resulting waves | Thermals= Sunlight heats the ground, heating up the air it touches, this warm air rises as thermals | Convective boundary air= is the air that is considered in the thermal, can be 1-4km by mid afternoon |Cloud streets/Horizontal roll vortices= rows of clouds, parallel to each other, product of cold-air advection & temp inversion | Valley wind= long wind blowing very gently upstream during daytime | Standard atmosphere= avg. variation of air pressure (P), temperature (T), and density (ρ) with altitude (see the spheres chart on back page, all of our weather happens in the troposphere) | CAPE index= thunderstorm index, the higher cape the more intense storm, 1750 is an ordinary thunderstorm and max thunderstorm is at 2850 | K index= rain intensity in thunderstorm 20-40 | Turbulence= the random gusty fluctuations (vertical and horizontal) of wind | Types of turbulence: Convective/free convection/thermal turbulence= due to buoyancy, warm air rising and cold air sinking. Wind-shear/forced/mechanical turbulence= different wind speeds or directions at different altitudes | Obstacle turbulence= caused by wind hitting an object and flowing around it | Wake turbulence= trail left behind by an aircraft as it flies | Froude number = small # means light winds and stable conditions, Fr # = 1 is most violent fluctuations, Fr infinity means lots of turbulent wakes behind the mountain aka chop (see image in back page) | Eddies = swirls of air motion | CAT= clear air turbulence, wind shear turbulence outside a cloud | Boundary layer turbulence caused by layers of the planets boundaries, is often weak to moderate, but enough to make passengers sick | Supercooled water/droplets= liquid water cloud/rain well below the freezing point, but freezes on aircraft/objects immediately upon impact | Two types of Ice on a plane = Clear ice (freezes a little slower roughly a sec but stronger and harder to remove) and Rime ice (white weak instant freezing ice easy to remove) | Modern planes have deicing or anti-icing systems within the planes, meaning that commercial planes shouldn’t really have issues |Front Types = If the cold air advances, it is a cold front. If the cold air retreats, it is a warm front. If the boundary doesn't move very much, it is a stationary front. | Occluded front= if a cold front catches up and merges with a warm front. See image on back side.| Isotherms are closer together in a warm and cold front and a close in an occluded front (but not as close/strong) than they normally are | Dry line= boundary between dry and humid air at roughly the same temperature. Squall line = band of thunderstorms associated with a cold front. Thunderstorms = Convective clouds, 3 types; basic, mesoscale convective systems and supercells | Thunderstorm Stages = 1) Cumulus: Updrafts, no downdrafts. No rain. No anvil 2) Mature: Both up and downdrafts. Rain. Anvil. Most violent stage 3) Dissipating: Downdrafts, no updrafts. Raining itself out, leaving ice crystals in the middle and upper parts of the cloud. Not very visible on radar | Downbursts= rapid descending downbursts of air, smaller ones are called microbursts. Downburst winds can be harmful to structures and they create outflow winds which could result in arc clouds or haboobs (sand storms)| Graupel= hail that has a smaller diameter of 0.5 cm | Hail is classified on the TORRO index ranging from 1-10 and is extremely dangerous to aircrafts. (0 = pea, 6 = egg, 10 = melon) | Tornados are violently rotating columns of air between thunderstorm clouds and ground, mos powerful one is supercell, measured on the Enhanced Fujita scale (EF) from 0 to 5 | TAF Terminal Aerodrome forecasts = future wind forecasts | SPECI as special report if METAR is not accurate to sudden weather change | Warm occlusion has cold coming close to warm, but warm still dominant. Cold occlusion has cold coming on to warm and cold is dominant | Unstable air is when you have warm air under cold air and that creates turbulence, cold air wants to sink and warm wants to go up. A thunderstorm results when the air mixes | Static stability: see image of equation on back side, corresponds to the calculated S value: Negative = statically unstable--air becomes turbulent, Zero = statically neutral—air is neutral (not turbulent nor non-turbulent), Positive = statically stable —air becomes non-turbulent| Low Pressure System Direction - Clockwise in southern hemisphere and Counter-clockwise in northern hemisphere. Directions are reversed for high pressure systems. Skiing: Pressure level map: black contours show lines of constant temperature, new line every Δ2°C. Pressure is used as a vertical coordinate much like meters: 100kPa = 0m, 95kPa = 500m, 90kPa = 1000m, 85kPa = 1500m, 80kPa = 2000m, 70kPa = 3000m, 62.5kPa = 4000m | NWP (Numerical Weather Prediction) is the analytical map that becomes the forecast map. These are merely predictions | Wind Barbs= see symbols chart on back page for corresponding values Convert m/s to km/h multiply by 4, or multiply knots by 2 | Relative Humidity (RH) = how much pressure that’s actually in the air to how much the air is able to hold. RH under 50% then no clouds, RH =70% means we start seeing cloud formations, RH = 90% then overcast cloud cover, if greater then may have little to no visibility!| If there is an unbroken “overcast” cloud layer under you then it is an undercast. | Condensation begins to appear when RH reaches 100% | Low pressure systems/cyclones = bad weather, can include heavy precipitation, strong winds and low visibility, not good to ski in. | Green on a kPa map indicates humidity and lots of clouds | Isobars show various pressure variations, when close together, suggest a cold/warm front incoming or occluded front | Low pressure troughs are marked with dashed lines, High pressure troughs with squiggly lines | High pressure is highest point (ridges) when isobars are increasing in pressure and low pressure is lowest point (troughs) when they are decreasing in pressure | Wind converges towards the center of the low, in northern hemisphere the Coriolis effect turns these winds to the right and so the air turns counter clockwise around a cyclone, opposite to a high pressure system | High pressure/anticyclone is when pressure is higher than surrounding regions, typically better more sunny less wind, more safe for skiing, lack of precipitation weather. Sometimes if low-pressure is incoming strong winds could be present | SLP= Sea level Pressure | Insolation= incoming solar radiation – visual light and ultraviolet (UV) radiation | Snow reflects 90% of light meaning that you get hit by Insolation twice, you would get sun burned | With approaching low pressure increasing high clouds can lead to flat light, clouds diffuse the light (when you can’t see bumps in the snow anymore). | Frontal zone= relative strong horizontal temperature gradient | Isobars are for pressure shown as full lines, Isotherms are for temperature shown as dashed lines | Frontal zone Indication are wind shift, pressure trough and higher relative humidity| In BC winds in front of cold front winds typically come from south-easterly to south and winds after a cold front typically come from north/north-westerly or south-westerly | Cold fronts indicate the boundary between relatively warmer and colder air masses, where the cold air is advancing | Long cold fronts and cold temperatures can lead to Hypothermia and frostbite | Wind chill is not the actual temp but rather the apparent temp/how cold it feels due to combined effect of wind and temp | As cold fronts approach then they can mix with warm fronts and create cumulonimbus with some precipitation cloud | Blowing snow, Heavy snowfall, clouds and fog cause less visibility (horizontal and vertical) | Convective showers are possible because air mass is typically unstable | Warm front = boundary between warm and cold air masses and the warm front is advancing | In the Northern Hemisphere midlatitudes, the winds ahead of a warm front typically come from an easterly direction. Behind the front, winds shift to be more southerly | Whiteout conditions= impossible to see anything |Behind warm front some convective clouds, showers are possible due to weak instabilities on air masses | Typically weak pressure gradient (a change of pressure across a horizontal distance) indicates light winds | 3 types of satellite imagery: visible (light gray image of clouds and earth, but can only see during daytime -> nighttime blindspot), infrared (IR) (shows radiation emitted, i.e. how hot/cold an object is) and water vapor (shows water vapor and not moisture) | Geostationary satellites match the rotation of the earth and can take loads of pictures from one place, but hard to see smaller features | Polar-orbiting (orbit on poles at low altitude) satellites can view small weather features and clouds but can’t always see the same area | Katabatic (drainage flow) winds lead to cold air pooling [can strengthen an already existing temperature inversion (higher altitude=higher temp)] these winds are typically created during night-time as the ground loses its heat source and starts to cool | Diurnal slope flow is created by thermal temp changes over the course of a day, as a result of the sun heating the earth’s surface (in turn heating up the air above it as well = relative heating) and then the earth’s surface cooling after the sun sets (which in turn cools the air) [radiative cooling]. This cycle happens during high-pressure system | As shallow layer of cold air moves downslope, it converges into small valleys, as these valleys become larger and eventually becomes a valley cold pool of air | Adiabatic lapse rate= change of temp with altitude | If a temp inversion traps moisture then it can create a valley cloud (when moisture condenses within the air in a valley) and rising air doesn’t travel higher, thus it’s a Capping Inversion | Inversions occur due to: subsidence (sinking motion) due to high pressure, and radiative cooling of the ground. | Clouds dissipate from the bottom up | Freezing fog = valley fog that occurs at temp below 0 resulting in supercooled droplets and rime ice |(orography = study of mountains)-- orographic uplift= when air lifts over mountains, as air lifts it cools down adiabatically [Δ10°C/km (dry) and Δ6°/km (wet)] | Dewpoint= air temp at which water vapour starts to condense into liquid droplets, if under air is under 0 degrees dewpoint is called frost point | Airmass transformation= as air falls down on other side of mountain it warms faster than it cooled on the way up (meaning hotter and drier air) | Lee shadowing/rain shadow= lack of rain and clouds in the lee of a mountain | Venturi/Bernoulli effect is the convergence of wind into a restricted area that accelerates it after it has passed the peak of the mountain (see illustration) | Wind-sheltered locations – mountain vallleys/treed areas, as they cause friction and turbulence that dissipate the wind | Tree bomb= lots of snow on a tree | Interpolation= estimating quantity at the in-between locations using the lapse rates as stated in orographic uplift under adiabatic conditions. In stable conditions, this lapse rate is very slow and so it’s negligible, likewise during a frontal passage there’s a very stable stable temperature profile and no vertical interpolation is needed. | Free-air temperature= temp at elevation with absence of heating and cooling from surface (from interpolation) | Factors affecting surface heating and cooling = sun angle (length of heating), cloud cover (more of it reduces amount of solar energy received) & wind speed (the greater the speed the more mechanical mixing, and the closer we get to the free-air temp) | Arctic fronts = large scale cold front air masses coming from north, very cold, dense, shallow and stable. Cannot easily move up over mountains due to density | Gap winds usually occur when the large scale prevailing wind direction is perpendicular (90 degrees) to the mountain range (frequent in BC). There are topographical gaps such as river valleys and mountain passes that the cold air can more easily move through, resulting in faster winds travelling through these valleys, also the pressure gradient drives this. | Rain-snow line is elevation at where the transition from rain to snow happens (water freezes), this line is 200300m below the freezing level on a mountain. You can extrapolate this by finding the 0°C isotherm elevation and subtracting 200-300 | Snow density= the amount of mass of ice and liquid per volume, it increases with higher temp and stronger wind | Convert snow density to water %, just divide by 10 and add % sign | Snow density is an indication of strength of snowpack, wind slab/wind board is newly-fallen snow can be very dense and well-bonded due to strong winds as it was landing, weird bumps on top of snow as a result of winds is called sastrugi, higher temperatures and faster wind speeds = more dense snow | Right side up snow = higher-density (heavy) snow underlying lower-density (lighter) snow, occurs when temp decreases (cold front) after storm cycle | Upside-down snow= higher-density snow overlying lower-density snow, typically a result of a warm front after storm cycle, high avalanche conditions since unstable | Snow pack is colder on top than bottom | Snow metamorphism = evolution of snow pack, faceted crystals/facets are created when a strong vertical temperature gradient exists. The water vapour is moving quickly, and crystal growth happens quickly. Faceting takes place when the temperature gradient is larger than 1°C per 10 cm depth/10°C per metre. Rounded crystals/rounds are produced when temperature gradients are weak, water vapour moves slowly, and crystal growth happens slowly rounding occurs when the vertical temperature gradient within the snowpack is less than 1°C per 10 cm depth/10°C per metre. | Snow pits= 1-2 meter deep holes to analyse snow for e.g. its layers and avalanche risk | Hand-hardness test = test each layers hardness first with fist then 4 fingers then 1 finger then pencil and knife | Types of snowpack layers = Weakbonded (newly fallen low density snow), Strong-bonded (e.g. wind slab) & Crust layer (rain or melt layer) | Storm snow= snow fallen within the last 48h | 3 snow climates: coastal (low avalanche, high density snow, frequent snowfall), transitional (frequent snowfall, moderate density, low avalanche) and continental (high avalanche, low density snow, low snowfall) | Deposition= when a substance undergoes a quick phase change from gas to solid without changing to a liquid state first | Surface hoar/hoarfrost/frost is frozen version of dew created with clear skies, temp inversion and flat surface | Surface Hoar / hoarfrost essentially the frozen version of dew. It is produced by deposition onto the snow surface when the air temperature falls below the frostpoint temperature. The outcome is the formation of ice crystals on the top of the snow surface, creating it requires a strong temperature inversion, calm winds, clear skies, flat open surface. Hoar is very feathery and delicate. When it's on the snow surface, it presents no danger. Once it's buried by subsequent snowfall, however, the surface hoar acts as a weak layer within the snowpack. With a layer of snow on top, the hoarfrost layer is prone to collapsing easily, since there are very few bonds between ice crystals and lots of empty air space, compared with the rest of the snowpack. This can cause an avalanche.| Persistent Weak Layer= weak faceted layers of snow that build up and persist over time, can be dangerous. | Avalanche= mass of snow that moves rapidly down the side of a mountain, types [SEE TYPES CHART ON BACK]= loose-snow/sluff made up of surface and/or near-surface snow that is not well-bonded. They begin at a single point, gathering more loosely-bonded snow crystals from the surface of the snowpack as they descend, gradually fanning out. (V-shape). Does not usually do any major structural damage/bury people, although it is possible. They’ll knock a person off their feet and carry them downhill. Could be deadly if it carries them into trees, over a cliff, or into a terrain trap. Terrain traps are typically small gullies. Even a small avalanche can quickly fill the small gully, burying you a couple of metres under the snow in the gully bottom. Wet sluff avalanches are often caused by significant snowmelt from strong solar radiation, or by significant rainfall on the snowpack. The snow has high liquid water content, it is more likely to be swept along, and the avalanche has more mass Wet sluffs are more common in springtime and in maritime snow climates, where mild temperatures and rain-on-snow events happen more often. | A slab avalanche occurs when a layer somewhere beneath the surface layer fails, and the cohesive layer(s) above it fracture into a block (or blocks) and slide downhill. A slab can propagate for tens or sometimes even thousands of metres. Since slab avalanches are typically larger and sluff avalanches, they tend to be more destructive and more likely to bury a person. Slabs that form due to high wind speeds in new snow are referred to as wind slabs. Slabs generally fall into two categories. Hard slabs are a result of high density, well-bonded snow (sometimes formed by high winds). They remain hard and cohesive blocks as they slide. Soft slabs are comprised of lower-density snow that has more bonding than newly-fallen, non-wind affected snow. Often, snow becomes bonded well enough to form a soft slab after about two days on the ground. The fracture is less likely to propagate as far in softer slabs, usually resulting in a smaller avalanche. The blocks also tend to break up more as they slide down the slope. Wet slabs are typically a springtime phenomena. The slab release results from meltwater or rain percolating through the snowpack, and a pre-existing weak layer becomes wet enough that its bonds lose strength and fail. | Snow crystals size is determined by humidity and temp. (See chart on bac...