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157 Cards in this Set
- Front
- Back
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Name the 4 basic clouds of vertical development.
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1. Cumulus (Cu).
2. Towering Cumulus (TCU). 3. Cumulonimbus (CB). 4. Altocumulus Castellanus (ACC). |
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Describe the amount of sky coverage indicated by the METAR terms. |
• CLEAR (SKC): no clouds are present • FEW: 2/8 or less of sky covered by cloud • SCATTERED (SCT): 3/8 or 4/8 of sky covered by cloud • BROKEN (BKN): 5, 6 or 7/8 of the sky covered • OVERCAST (OVC): 8/8 coverage |
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CLEAR |
NO Clouds |
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FEW |
2/8 or less |
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SCT |
3/8 OR 4/8 |
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BKN |
5,6,7/8 |
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OVC |
8/8 |
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At a temperature higher than 15 the altitude may be _____ than indicated |
Higher |
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At a temperature lower than 15 the altitude may be _______ than indicated. |
Lower |
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Buys Ballot's Law
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In the northern hemisphere (Canada for example), if you stand with your back to the wind, the area of LOW pressure is always to your left.
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Air spins in what directions for lows and highs? |
Lows-Counterclockwise Highs-Clockwise |
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What are the general weather conditions for areas of high pressure? |
High pressure systems are generally indicative of good weather and cover several hundreds even thousands of kilometers in diameter
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State the name of the two basic cloud forms.
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Stratiform - in horizontal layers .Stratus clouds most often have very small vertical motions associated with them. Cumuliform - as the result of rising air currents.Cumulus clouds have significant vertical updrafts and downdrafts. |
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Describe the 4 basic clouds of vertical development. |
1. Cumulus (Cu).Towering Cumulus (TCU),Cumulonimbus (CB):The first three basic clouds listed above get progressively larger and potentially more severe as the vertical updrafts and downdrafts are enhanced through growth. ACC-displays vertical growth and is the result of mid -level instability. This cloud is often a telltale sign of impending thunderstorm development. |
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Describe: Cumulus (Cu).
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Detached clouds, generally dense and with sharp outlines, developing vertically in the form of rising mounds, domes or towers, of which the bulging upper part is often like a cauliflower. Their sunlit parts are mostly brilliant white and their bases are relatively dark and nearly horizontal. Sometimes Cumulus clouds are ragged.
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Describe:Towering Cumulus (TCU),
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Another name for cumulus congestus, it is a rapidly growing cumulus or an individual dome-shaped clouds whose height exceeds its width. Its distinctive cauliflower top often mean showers below, but lacking the characteristic anvil of a cumulonimbus, it is not a thunderstorm.
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Describe:Cumulonimbus (CB):
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Thundercloud - Heavy and dense cloud, with a considerable vertical extent, in the form of a mountain or a huge tower. At least part of its upper portion is usually smooth, or fibrous or striated, and nearly always flattened; this part often spreads out in the shape of an anvil or a vast plume. Under the base of this cloud, which is often very dark, low, ragged clouds frequently occur either merged with it or not.
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Describe: Altocumulus Castellanus (ACC).
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White or grey, or both white and grey, patch, sheet or layer of cloud, generally with shading, composed of laminae, rounded masses, rolls, etc., which are sometimes partly fibrous or diffuse and which may or may not be merged; most of the regularly arranged small elements usually have an apparent width of between one and five degrees.
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State the aviation significance of the presence of CU, TCU, CB and ACC in general.
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Some clouds may contain strong winds, heavy rain, thunderstorm, hail, etc.
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State the aviation significance of the presence of TCU
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Rough to very rough air. Significant Icing if above freezing level, strong updrafts below and in cloud.
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State the aviation significance of the presence of CB
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Thunderstorm activity, precipitation, winds, violent vertical currents, hail often present, extreme turbulence, extreme icing, lightning
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State the aviation significance of the presence of ACC
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turbulence, precipitation, icing
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State the aviation significance of the presence of CU
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bumpy flight in and beneath cloud, can develop into cb and tcu, updrafts below and in cloud
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Explain the term “atmospheric pressure”.
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-due to the weight of the overlying air, from the surface of the earth to the top of the atmosphere. -Most of this weight is confined to the troposphere. As a result of gravity, the distribution of air molecules is greatest near the ground and decreases with height. -can be measured using inches of mercury, Hectopascals ( kilopascals). Millibars. |
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Differentiate between station pressure and mean sea level pressure.
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Station Pressure:actual atmospheric pressure at the elevation of the observing station(the weight of column of air extending from a station to the top of the atmosphere) This value is determined directly from the barometer at the observing station. Mean Sea Level Pressure:Standardizing pressure to sea level is important because the surface pressure is not the same over the entire surface of the Earth. Above mountains, pressure will seem lower than above valleys. We account for this pressure disparity by standardizing pressure to Mean Sea Level. |
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How do Station Pressure and Mean Sea Level Pressure Compare?
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To compare the pressures at stations with different elevations, station pressure must be reduced to a common level. The level taken as a standard is mean sea level (MSL). The reduction to MSL is calculated by adding to the station pressure the weight of an imaginary column of air extending from station to MSL. Since the weight of this column will depend upon its temperature, some assumption must be made about the temperature of the imaginary air column. The sea-level pressure is used to represent the pressure distribution on weather maps. In calculating it, the temperature assumed for the imaginary air column extending from station level to sea level is based on the average of the surface temperatures at the time of the observation and 12 hours before the time of observation. |
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Differentiate between mean sea level pressure and Altimeter Setting.
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Altimeter setting: is a pressure which, when set on the subscale of an aircraft altimeter, will cause the instrument to indicate its true height above MSL, when the aircraft is situated on the airport runway for which the altimeter setting is given. -lso a pressure reduced to sea level, but the temperature assumed for the imaginary column is different. In this case, the temperature at MSL is always taken to be 15oC and it decreases from MSL to station level at the rate of 1.95oC per 300 meters. -For aerodromes situated not far above sea level, the altimeter setting and the sea level pressure are approximately equal when expressed in the same units, and sometimes can be used interchangeably |
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State the isobaric interval used on weather maps.
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The distance between two lines identify a pressure difference of 4 hectopascals, either increasing or decreasing in value.
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Define an isobar.
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-To visually represent the variations of atmospheric pressure across the continent, at any given time, computers analyse and draw lines called “isobars”. -Isobars are curved lines drawn on a surface weather map that join areas of equal barometric pressure. -Like contour lines on a topographic map, Isobars form roughly concentric circles that outline high and low pressure areas. |
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With respect to pressure systems, define:
- High - Low |
a HIGH is a region of relatively high pressures with pressure values increasing or becoming higher towards the centre. may be called an anticyclone. a LOW is a region of relatively low pressure values decreasing or becoming lower towards the centre. may be called a cyclone or a depression |
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With respect to pressure systems, define:
- Trough - Ridge |
Trough- bulge in low pressure area Ridge-bulge in high pressure area |
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State the general circulation (air movement or wind) around a high or a low.
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-Rule # 1 (Buys Ballot's Law): In the northern hemisphere if you stand with your back to the wind, the area of LOW pressure is always to your left. -Air blows counter-clockwise around a Low, Air blows clockwise around a High. |
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Describe the general vertical motion at the centre of a high and at the centre of a low.
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Low-The air is deflected by friction to the centre of a low. It accumulates and rises at the centre. As a result, at the centre of a low, air rises, expands, cools, and clouds form. High-At the centre of a high, the air flows out ( towards low pressure ). It sinks, heats and skies tend to be clearer. |
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Describe the general weather conditions
normally associated with: - Low - Trough - High - Ridge |
-High pressure systems are generally indicative of good weather and cover several hundreds even thousands of kilometers in diameter. -Low pressure systems are generally indicative of bad weather and cover from 10 km to hundreds of kilometers in diameter. |
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Define “ pressure gradient” and explain its relationship to wind speed.
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-Rate of change of pressure with horizontal difference measured in kms. The speed of wind is directly proportional to the pressure gradient. The faster the pressure changes, the stronger will be the winds. |
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Define “ pressure gradient” and explain its relationship to wind speed.
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-When isobars are closely spaced or the pressure gradient is steep, a pressure change of 4 hPa occurs in a relatively short distance, and a LOW is termed “deep”; a HIGH is termed as “strong -When isobars are widely spaced or the pressure gradient is weak, a pressure change of 4 hPa occurs in a relatively long distance. and a LOW is termed “shallow”; a HIGH is termed as “weak” -Wind speeds vary depending on the area on the surface map. Think of pressure gradient as indicating how steep a hill is. The closer the isobars, the steeper the hill. The balls on the right will roll down the hills at different speeds. |
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What type of pressure values are plotted on a surface weather chart?
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Mean sea level pressure.
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Indicate which of the following terms refer to highs:
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strong,weak
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Indicate which of the following terms refer to lows
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deep,shallow
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Define “ wind ” and state the units used.
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The horizontal movement of air is known as “wind”. Wind speeds, for aviation purposes, are expressed in knots (nautical miles per hour). For Weather reports, Area and Aerodrome forecasts the wind is always reported in degrees True. For ATIS (Automatic Terminal Information Service) broadcasts and in the information given by the tower for landing and take-off, the wind is reported in degrees Magnetic. Horizontal pressure difference caused by an unequal distribution of temp in the atmosphere cause the air to move. Warm air rises, as air is heated, it becomes less dense. As warm air rises, cooler air which is more dense flows in to take its place. The air tends to move horizontally from an area of high pressure to an area of low pressure. This phenomenon creates movement of the air - the wind. The wind direction is reported as being the direction from which the wind is blowing (a 270° wind is blowing from the west). The speed of the wind is reported in Knots (nautical miles per hour). |
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State “Buys Ballot’s Law”.
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-Rule # 1 (Buys Ballot's Law): In the northern hemisphere if you stand with your back to the wind, the area of LOW pressure is always to your left. In the northern hemisphere,pressure gradient force + the Coriolis force cause the air to flow parallel to the isobars, in a clockwise way around a high, and in a counter clockwise way around a low. The opposite holds true in the Southern Hemisphere. |
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Given a METAR, determine the wind direction and speed.
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METAR 291100Z
CYQR 291100Z 22015KT 10SM TSRA BKN023 OVC060CB 15/14 A2989 RMK SC5CB3 LTNG ALQDS SLP120 WIND DIRECTION Wind direction is normally described in three digits and refers to the direction from which the wind is coming WIND SPEED Wind speeds are two digits (or three digits if required), in knots. "00000KT" is a calm wind. In the example below we have a wind speed of 15 knots. |
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What is a metar?
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METAR is the name of the international meteorological code for an aviation routine weather report.
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Given a METAR, determine the variable wind.
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METAR 021500Z
CYSF 021500Z 18010KT 140V220 15SM FEW240 15/08 A3022 RMK CI1 SLP243= First three digits are direction to the nearest 10 degrees true. VRB is variable direction if 3 knots or less, or with thunderstorms. 00000KT is calm. Variation in wind direction gives the two extreme directions in clockwise order (during the previous 10 minutes). This group is reported only if occurring, otherwise it is omitted. Only a total variation of 60 degrees or greater is included. In the example below the wind is at 10 knots and varies from 140 degrees to 220 degrees. |
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Describe the effect of Coriolis force on the circulation of wind around high and low pressure areas.
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The moving air caused by the pressure gradient force is immediately acted upon by another force which is due to the earth’s rotation; (on a non-rotating earth, wind would flow directly from a high to a low pressure area). This force is known as the “Coriolis Force”. While it doesn’t cause wind, it does affect the direction of the air movement.
Because of the earth's rotation, in the northern hemisphere, as the air moves from a high pressure to a low pressure area, the Coliolis force deflects the moving air to the right. In the southern hemisphere the air deflects to the left. -The result is that the air will flow parallel to the isobars. |
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Explain the change in wind velocity with height in the lower 3000 feet of the atmosphere.
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Friction at the surface and up to about 3000’ causes the wind to
1) slow down 2) flow into a low pressure area 3) flow out of a high pressure area The friction diminishes with height, therefore the wind veers and the speed increases. |
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Define veering and backing as they relate to changes in wind direction.
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Veering
A veering occurs when the wind makes a clockwise change in direction. Backing A backing occurs when the wind makes a counter-clockwise change in direction |
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Given a meteorological surface map, determine the direction and speed of the wind
at various locations. |
On a surface map, the line with hooks at one end indicates wind direction and wind speed. The line is always plotted to indicate the direction from which the wind is blowing (towards the dot). The number of "hooks" denotes the speed in knots in factors of 10 knots. If there was a wind of 15 knots, the arrow would have 1 and a half "hooks" at the end of it. |
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Define “ wind shear.”
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Wind Shear is “A change in wind speed and/or wind direction in a short distance. It can exist in a horizontal or vertical direction and occasionally in both.” Wind shear is the sudden “tearing” or “shearing” effect encountered along the edge of a zone in which there is a significant change in wind speed and/or direction. Shear can occur at any level. |
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Define Directional Shear.
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When two winds in opposite direction (or different directions) meet, we have a Directional Shear.
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Define Speed Shear.
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When two winds are close together but at different speeds, we have a Speed Shear.
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Describe the effects of wind shear on aircraft performance.
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Increase performance: tail wind change to headwind, wind speed increase with descent Decrease performance:headwind change to tailwind, wind speed decrease with descent |
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State areas in flight or near the ground where wind shear may be found.
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In flight
• lower 3000 feet (due to changes as result of less friction) • frontal surfaces • jet streams • temperature inversions (an increase in temperature with height or altitude) Near the ground • frontal shear. • associated with thunderstorms • temperature inversions • physical obstructions - buildings. - hills. |
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Describe the "Jet Stream".
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The Jet Stream is a narrow band of exceedingly high wind speeds in the upper levels of the troposphere.
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State the altitude range where jet streams are normally found in Canada.
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• Normally found between 20,000 and 40,000 ft.,
• Higher in the tropics than over the poles • Generally associated with a frontal system • Higher (in altitude) in the summer than the winter |
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State the typical values for the following jet stream characteristics.
- horizontal and vertical extent - jet stream core maximum winds |
horizontal and vertical extent : Thousands of miles long, A few hundred miles wide, few thousand feet thick. jet stream core maximum winds: A minimum wind speed of 60 knots,core wind speeds can attain 250K, but generally range between 100 and 150 knots. |
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On a non-rotating earth in the northern hemisphere, the wind would blow:
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Perpendicular to the isobars.
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The wind will go from an area of ____ pressure to an area of _____ pressure. |
From an area of high pressure to an area of low pressure.
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State what determines the amount of water vapour the air can hold.
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The air can hold a large amount of water vapour depending on its temperature. The warmer the temperature the greater the capacity to hold water vapour.The actual amount of water vapour in the air is indicated by the dew point temperature. This is the temperature to which air would have to be cooled to achieve saturation. If the air continues to cool, condensation or sublimation will occur and fog or clouds tend to form.
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Explain the terms: Water Vapour, Condensation, Sublimation, Evaporation, Heat
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Water Vapour: water in gaseous form. Condensation: The process whereby water vapour turns into water Sublimation:Change of state from the gaseous state to the solid state or vice-versa Evaporation: The change of state from liquid to the gaseous state. Heat:A form of energy in the process of being transferred from one object to another because of their difference in temperature. |
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Define “relative humidity”.
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The ratio of the amount of water vapour actually in the air compared to the maximum amount of water vapour the air can hold at that particular temperature (expressed as a percentage).
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Define absolute humidity
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The amount of water vapour contained in a unit of air (or the mass of water vapour (gm) / volume of air (m3)). |
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Define Water Vapour Content
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Water vapour content is defined as the quantity of water vapour present in the air. It determines to a large extent the type of atmospheric conditions. Water vapour content in the air is expressed as absolute humidity, relative humidity or as dew point temperature. |
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Explain what is meant by the term “saturated air”.
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The condition in which the amount of water vapours is the maximum possible at the existing temperature. When the relative humidity reaches 100%, the air is saturated for that particular air temperature. The lower the temperature, the lower the quantity of water vapour that can be present in a given volume.Higher moisture content means more cloud can form. Colder Air - Water vapour molecules are closer together. Warmer Air - Water vapour molecules have more room. |
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Define "dew point".
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The dew point is the temperature, expressed in degrees Celsius, to which air would have to be cooled to achieve saturation.
The dew point temperature (Td) is also an indicator of the air’s actual water vapour content. |
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Describe “stable and unstable” conditions as they relate to the vertical motion of the air.
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Stable: air that will resist upward or downward displacement, and tends to return to its original horizontal level, is said to be stable. because the lifted(air becomes colder and denser than the surrounding air and thus sinks.) Unstable: air which tends to move further away without additional air is said to be unstable.(lifted air becomes warmer and lighter than the surrounding air and is buoyant.) **A rising water vapour molecule cools at a rate of approximately 10°C per kilometer. As it cools, if saturation is attained, fog and clouds will form |
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State the flight characteristics of stable air.
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• low visibilities, fog may occur. • stratus type cloud. • steady precipitation. • consistent, steady winds. • smooth flying conditions (often IFR with respect to ceiling and visibility). |
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State the flight characteristics of unstable air.
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• good visibilities ( vertical currents carry away impurities ). • vertical development type clouds. • showery precipitation. • gusty winds. • bumpy flying conditions. |
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Describe the processes involved with respect to the following 3/5 lifting agents: - Convection - Orographic lift - Frontal lift |
Convection: air is heated from below from contact with surface of earth. Rising columns of air(thermals) are usually separated by areas of sinking air. Orographic Lift: air is forced to rise up sloping terrain. depends on stability of lifted air Frontal lift: air is forced to rise by a wedge of colder and denser air. Cold fronts are advancing cold air which undercuts the warm air. Warm fronts retreat cold air and the warm air overruns the denser air. |
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Describe the processes involved with respect to the following 2/5 lifting agents: - Convergence - Mechanical Turbulence |
Mechanical Turbulence: lift caused by friction between air and ground. The air is "mixed up" into a series of eddies. Depends on strength of wind and roughness of terrain. Convergence: occurs at the centre of low pressure areas. Air converges at this point and is forced to rise, resulting in cloud and precipitation. |
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Define: lifting agent |
force pushing air upwards
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list the 3 requirements for condensation to occur
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Saturation,Cooling process,Condensation nuclei
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Define "air mass".
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Air mass is defined as a large section of the troposphere with relatively uniform properties of temperature and moisture in the horizontal. An air mass may be several thousand miles across.An air mass takes on its original properties from the surface over which it has formed.
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Differentiate between maritime and continental air masses.
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All air masses are described by both humidity (humid or dry) and temperature (cold, temperate or warm).
MARITIME Air Masses • The air mass is formed over a large body of water. • The air mass is humid. CONTINENTAL Air Masses • The air mass is formed over a large land area. • The air mass is dry. |
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State the temperature regime terminology normally associated with air masses.
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Arctic for a cold air mass.This air mass is formed in the Arctic or high latitudes Polar for a temperate air mass ( permafrost line to 30 ° N ).(warm) Tropical for a warm air mass (30 ° N south to the equator ).This air mass formed in the Tropics or low latitudes.(very warm) |
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State the name, from coldest to warmest, of the 4 primary air masses which affect North America.
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cA, mA, mP, mT AKA Continental Arctic, Maritime Arctic, Maritime Polar, Maritime Tropical ** Continental Polar(cP) and Continental Tropical can occur but seldom appear in North America |
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State the characteristics of cA.
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Forms over frozen arctic in winter during long winter night
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State the characteristics of mA.
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Forms from cA as it moves south during the winter over cold ocean waters. In summer it forms over open water of Arctic Archipelago or the numerous Northern lakes of North America(Tundra) |
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State the characteristics of mP
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Forms over large areas of oceans of temperate latitudes. Forms from mA as it moves south over ocean, forms from mT as it moves north over great stretches of ocean, forms from mA as it moves down the continent, forms from mT as it moves up the continent. |
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State the characteristics of mT
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Forms over tropical oceans including Gulf of Mexico, South Atlantic and South Pacific
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State the 3 factors which determine the weather in any given air mass.
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1. The moisture content. 2. The cooling process. 3. The stability of the air Maritime air-high moisture means clouds form **Even if the air is moist, cloud formation can only occur if the air is cooled. |
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The cooling processes that contribute to the formation of clouds are:
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• Air being in contact with relatively colder ground cooling by radiation. • Advection of warm air over a colder surface. • Expansion brought about by a lifting process. |
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Describe the process by which air masses are modified.
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As they move they acquire the temperature and moisture characteristics of the underlying surface.Requires an extensive time over the new surface in order for significant modification to occur. **There may be up to four air masses in the winter and three in the summer over North America. Thus it is possible to find three frontal systems on weather maps in the winter, and two in the summer. |
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Define the term “front” as used in meteorology.
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A “front“ is the transition zone between two air masses. Across this transition zone, temperature, moisture content, pressure and wind can change rapidly over a short distance. The front is often an area of intense weather significant to aviation. |
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What fronts exist in meteorology in summer in North America?
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During the summer season, only two fronts exist; the Maritime (M) front and the Polar (P) front. Depending on the movement of the air masses, there will be cold fronts (advancing cold air), warm fronts (retreating cold air) or stationary fronts (neither advancing or retreating). |
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What fronts exist in meteorology in winter in North America?
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During the winter season, there will be three fronts: the Arctic (A), the Maritime(M) and the Polar(P) fronts. Depending on the movement of the air masses, there will be cold fronts (advancing cold air), warm fronts (retreating cold air) or stationary fronts (neither advancing or retreating). |
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Explain in basic terms the “Polar Front Theory”.
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The POLAR FRONT THEORY essentially states that the earth is covered by polar (cold) air in polar regions and tropical (warm) air in the equatorial regions. They are separated by the Polar front. This is a 2 air mass 1 front model.We rarely experience 3 rapid frontal passages. When it does occur it often takes months to go from CA to MT or vice versa. However, because a frontal boundary is not a straight line we often alternate from one air mass to another over short periods. Think of summer that is hot and humid, then a cold front (drier and warm) arrives, and is later replaced by the hot and muggy conditions again. This is the sequence, MT air, cold front passage to MP air, warm front passage back to MT.
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Name the two types of Fronts
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Warm front:where warm air, advances on colder air causing the warmer, less dense, air to rise. Cold front:where cold air, advances on warmer air causing that warmer air to rise. |
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Define: Cold Front
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A Cold Front is a transition zone between advancing cold air and warm air. An arrow end is used to identify a cold front. |
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Define: Warm Front |
A Warm Front is a transition zone between warm air and retreating cold air. A half circle is used to identify a warm front. |
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Define: Stationary Front |
A Stationary Front is transition zone between two air masses that are not moving. Alternating arrow ends and half circles are used to identify a stationary front. |
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Identify the weather map symbology used to identify: a) a Cold Front b) a Warm Front c) a Stationary Front |
A blue arrow end is used to identify a Cold Front.
A red half circle is used to identify a Warm Front.
Alternating arrow ends and half circles are used to identify a Stationary Front. |
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State the underlying factors that determine the weather at a cold or warm front.
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Lift creates cooling which often produces cloud and precipitation. Severity of the weather created by the front depends on the following factors: 1. The slope of the frontal surface. 2. The speed of frontal movement. 3. The temperature of the lifted air mass. 4. The moisture content of the lifted air mass. 5. The stability of the lifted air mass |
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Describe the weather changes generally associated with the passage of cold and warm fronts. |
The passage of a warm front will result in an increase in temperature. The passage of a cold front will generally result in a decrease in temperature. In the case of a cold front, the temperature change usually begins when the front reaches the station. In the case of a warm front, the temperature change may begin before the front reaches the station due to the proximity of the warm air to the surface as the depth of cold air over the station decreases (as illustrated in the diagram on the right). Although a cold front usually brings a decrease in temperature, sometimes it brings, for a short period of time, a slight increase before the drop.This slight increase of temperature accompanying the passing of a cold front occurs only at the surface where the ground has been heated and does not affect the upper levels. We can therefore expect low level convection to occur since low level heating will destabilise the air. |
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Weather and Fronts - What happens to dew point temperature with a frontal passage?
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As temperatures change with the passage of fronts, we can also expect a change in the moisture content of the air.
With a warm frontal passage, dew point temperatures generally increase and with a cold frontal passage, dew point temperatures decrease. |
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Describe the conditions that would produce icing.
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-aircraft must be flying through visible water in the form of rain or cloud droplets-when the liquid water droplets strike, their temperature or the temperature of the surface must be 0° C or below. -clouds formed at temperatures below - 20°C will usually be composed of ice crystals-heaviest icing usually occurs in the range from -9 to 0 degrees C
-The larger the super-cooled droplets, the more serious the icing will be. The size of the droplets in the cloud is determined by the degree of turbulence and the stronger the rising currents, the larger the droplets that can be supported. Thus, the most serious cloud icing will be encountered in cumulus type clouds or in clouds forming in the rising air along a mountain slope or a frontal surface. |
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Describe the effects of icing on an aircraft in flight
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The rate of accumulation of icing may vary from less than one-half inch per hour to as high as one inch per minute for brief periods. Experiments have shown that an ice deposit of one-half inch on the leading edge of some types of air foils will reduce lift by about fifty percent, increase the drag by an equal percentage, and greatly increase the stalling speed. The weight of the ice is not a major factor until compounded by the loss of lift associated with the formation of the ice on the wings.
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Describe 4 types of ice that can form on an aircraft.
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Clear, Rime, Frost, Mixed,Clear
-Clear ice is a transparent or translucent coating of ice which has a glassy surface appearance. Very difficult to remove. Clear ice usually forms on the leading edges of wings, antennae, etc., and spreads back, tapering along the wings. Build-up is usually more rapid than that of rime ice. Rime-Rime ice is a white or milky, opaque, granular deposit of ice which accumulates on the leading edges of wings, antenna, etc.. Rime ice usually accumulates on the leading edges of exposed parts and projects forward into the air stream. It generally shows little or no tendency to adhere to the contour of an air foil outside of a limited region near the centre of the leading edge and its accumulation rate is generally much slower than that of clear ice. Frost-Frost is a light, whitish, feathery, crystalline structure of snow-like characterstics formed by sublimation when the surface temperature falls below 0ºC. It is created when the aircraft flies from a region where the temperature is well below 0ºC to a region where the temperature is considerably higher and where the humidity is relatively high.hardly visible increase in stalling speed and the distortion to the normal airflow over the wings and control surfaces will adversely affect the take-off characteristics of an airplane. a take-off may be impossible. Mixed-Mixed ice is a mixture of clear and rime ice. |
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Describe the three intensities of icing
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Light, Moderate, Severe
Light - there is not normally a problem unless the aircraft is exposed for a lengthy period of time. Moderate - a diversion might be essential since the rate of accumulation is such that there is a potential for a hazardous icing situation. Severe - the rate of accumulation is such that anti-icing and de- icing may fail to reduce or control the hazard. A change in heading or altitude is considered essential. Precise definitions of these terms are difficult to develop since the intensity of an icing situation for particular flight depends on the type of aircraft. |
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List the prevention and control measures used to reduce the effects of icing.
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Fluids, Heating Devices, De-icer Boots, Change in altitude.
Essentially, a fluid is an anti-icing device since it is applied when ice begins to form. Propeller blades and wind screens are often protected in this way. Heating devices fall into the category of anti-icing equipment. This system is the most effective and can be of two types, electrical and exhaust. Critical areas are heated prior to entering icing conditions and therefore the ice is immediately evaporated as it strikes the aircraft. By pumping air intermittently under the rubber covering, it can be made to pulse in such a way that any ice on it can be cracked and broken off. This system is only effective when turned on after ice has formed. |
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Describe under what conditions carburetor icing may occur and how the pilot can reduce the possibility of carburetor icing occurring
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Where to find answer? |
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State the composition of the Atmosphere.
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Nitrogen: 78,09 %
Oxygen: 20,95 % Carbon Dioxide: 0,03 % Ozone: 0,000003 % Water Vapour: 0to 3 % |
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Wheredoes most weather occur? Why?
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99% of weather occurs in the lowest 35,000 feet of the atmosphere. It is where thegreatest concentration of water vapour occurs.
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Explainthe importance of water vapour as an atmospheric gas. |
Watervapour is always present in the atmosphere, even in the desert. The conversion of this gas into a liquid(water) or solid form (snow, ice) and vice–versa (e.g. from snow to water and to gas) has a great impacton aviation. This is because of thechange in visibility. |
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Explainthe significance of minute solid particles present in the atmosphere. |
These solid particles are essential in the process ofchanging water vapour into liquid waterdroplets or into solid ice crystal form. May be present in sufficient amountsto reduce visibility seriously.
Under more severe conditionssuch as freezing rain or hail, the effect can be as critical as not being able to fly the airplane.Rotors may be blocked by ice, wings maybe frozen. |
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When does precipitation occur? |
Precipitation occurs when water vapour bindswith minute solid particles in theatmosphere to cause water droplets. Water droplets can collide with other dropsand gradually grow in size. They gainmomentum until they fall through the air as rain.
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Define:condensation nuclei or crystallisation nuclei. |
the process ofchanging water vapour into liquid waterdroplets or into solid ice crystal form. In |
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Describethe three properties of the atmosphere. |
Airis Mobile (Mobility), Air can be Compressed (Capacity for Compression), Air canbe Expanded (Capacity for Expansion): factors of compression, expansion, and mobility of air: Whenair is forced to rise, it reaches areas of lower atmospheric pressure, air expands and cools. • At a given point thetemperature drops to a point where condensation will occur. At that level, cloud will form. • The reverse is also true, sinking airis heated by compression and cloud willthen evaporate. |
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Describethe lowest three divisions of the atmosphere.
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troposphere:closest to earth,heated more intensely than the upper levels(because atmosphereis heated from below)
tropopause:theboundary line between the troposphereand the layer above,average height 11km, higher in warm air than it is in cold air(8km north pole, 18equator), changes with seasons, changes abruptly near jet streams stratosphere:no water vapour, no major vertical aircurrents,the temperature may remain relatively constant or actually increase with height due tochemical activity of the ozone layer,from 0 to 10, 15km or 50,000 feet thick layer |
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Describe the properties of the ICAO Standard Atmosphere. |
1.The air is a perfectly dry gas. 2. A mean sea level pressure of 29.92 inches of mercury 3.A mean sealevel temperature of 15. 4. Therate of decrease of temperature withheight is 1.98 degrees per 1,000 feet |
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When the conditions of the ICAO standards how will the altimeters show?
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Whenthe four conditions of the ICAO standards are met, both the Radar Altimeter and the Pressure Altimeter willshow the same values.
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Cold Temperature Corrections– ISA(ICAO Standard Atmosphere)
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Because the truealtitude will be different from indicated altitude in cold temperature conditions, the pilot would have tocalculate the altitude correction factorand add it
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Define:Minimum vectoring altitude(MVA)
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lowest altitude for vectoring aircraft by atc that meet obstacle clearance and radio coverage requirements in the defined airspace
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A- When temperature is higher what happens in regards to true altitude?
B- When will an altimeter show true altitude? |
A-The true altitude may actually be higher than indicated.
B- When all four ICAO Standards are met |
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Describe the basic requirements for the formation of a thunderstorm.
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1) Unstable air (especially if unstable to High levels). 2) Some form of lifting action - to get the air moving upward. 3) Air with a high moisture content. |
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Describe the 3 distinct stages in the formation of a thunderstorm.
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The Cumulus Stage: formation of a cumulus cloud that gradually builds up into a towering cumulus. updrafts support water=no precipitation The Mature Stage:characterized by a build up into TCU/CB with very high tops.updrafts may attain 6000 feet/min, water droplets start falling and drag air down with them, producing downdrafts in the 2000 ft/min range. most if not all precipitation occurs here. violent turbulence/ lightning microbursts, gusts fronts, hail, tornadoes, heavy precipitation associated with mature stage The Dissipating Stage: onset of precipitation is the key to the dissipation of the thunderstorm cell. The precipitation cools down the lower part of cloud, and breaks the updrafts that are the main source of its energy. The top of the cloud spreads out into an anvil form. |
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Describe 2 main types of thunderstorms.
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Air Mass Thunderstorms: usually form as the result of convection or orographic lift. Form individually or in clusters. Large clusters are collectively known as supercells. Frontal Thunderstorms:most often associated with cold fronts but also occur with warm fronts. They usually form in a solid line several hundred miles long and in various stages of development. Warm front thunderstorms are often embedded in the main cloud deck and not as visible as cold front thunderstorms. |
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What thunderstorm types are air mass and what kind are frontal?
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Air Mass: Convection, Advection over land and water, Orographic Frontal: Cold Front, Warm Front |
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What are the concepts related to air movement?
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• Gust Fronts. • Downbursts. • Downdrafts Speed. |
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Describe a “gust front” as it relates to thunderstorm activity.
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A gust front is the result of the strong downdrafts in the mature stage of a thunderstorm which reach the ground and spread out horizontally. There is usually significant turbulence associated with this phenomenon.
Nearly all thunderstorms produce some degree of gust front. |
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Describe 2 types of downbursts.
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A macroburst is a large downburst with a diameter of 2 miles or more when it reaches the earth’s surface. Damaging winds can last from 5 to 20 minutes. A microburst is a downburst of less than 2 miles in diameter and of short duration, typically less than 5 minutes. They can be classified as wet (with precipitation) or dry (without precipitation).Speed- approach approx. 6000feet/minute and winds of 80 knots |
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Define and explain Virga associated with Thunderstorms.
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Definition: precipitation falling but not reaching the ground associated with TCU and CB are often precursors of microbursts. The virga evaporates below the cloud and, as a result of the heat required for evaporation, the air in these regions becomes colder than its environment, sinking rapidly and accelerating downwards. |
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State the vertical downdraft speed often associated with microbursts.
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Downward vertical winds can attain speeds as high as 6,000 feet/min (110km/h). Outward horizontal wind gust speeds can reach up to 80 knots (140km/h) at tree top level.
The microburst downdraft shaft can have a diameter of up to 6,000 feet (1.8km).
At ground level, the vortex ring can have a horizontal extent of up to 2 1/2 miles (4 km) from the centre of the microburst.
Microbursts do not have a long life span, lasting typically about 10 to 20 minutes, with the maximum wind intensities occurring about 5 minutes after ground contact and lasting for about 2 minutes. |
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Define downburst
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A severe downward rush of air and its outbursts of damaging winds
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List the 9 areas of concern when flying in or near a thunderstorm.
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• Turbulence • Hail • Lightning • Icing • Squall lines • Tornadoes • Low ceilings and visibilities • Heavy rain showers • Microbursts |
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Describe the 9 areas of concern when flying in or near a thunderstorm: Turbulence.
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Hazardous severe turbulence is present in all cumulonimbus cloud. In cloud, the strongest turbulence occurs in the shear zone between the up and down drafts (generally between 12,000 and 20,000 feet in the mature stage). Strong turbulence can affect aircraft by damaging airframes, and causing abrupt changes in aircraft speed, attitude and altitude. |
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Describe the 9 areas of concern when flying in or near a thunderstorm: Hail.
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Hail occurs in the mature stage of cells that have updrafts of more than usual intensity. The maximum occurrence of hail is at around 10,000 to 15,000 feet (3,000 to 4,500 metres) Hail can cause damage to the airframe, windshields, and outside instrument sensors of the aircraft. |
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Describe the 9 areas of concern when flying in or near a thunderstorm: Lightning.
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Lightning is the visible electric discharge produced by a thunderstorm. It occurs in-cloud (also called sheet lightning), cloud-to-cloud, cloud-to-ground, and occasionally cloud-to-clear air. Lightning is always present in or in the vicinity of cumulonimbus clouds. most prevalent in cumulonimbus cloud between the temperatures of +8° and –8°C (at ± 5000 feet from the freezing level) electricity generated by thunderstorms is rarely a great hazard to aircraft but may cause the following problems: • Puncture the skin of the aircraft. • Damage communication and navigational equipment. • Temporally blind pilots. • Induce errors in magnetic compasses. • Disrupt low and medium radio frequencies. • More rarely, ignite fuel vapours. |
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Describe the 9 areas of concern when flying in or near a thunderstorm: Icing.
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When an aircraft flies at or below freezing temperatures and strikes supercooled water droplets, the droplets will freeze and adhere to the aircraft. Dangerous icing can occur in thunderstorm clouds. Clear and mixed icing is possible in all stages of development of thunderstorm clouds but severe clear icing is most likely in the upper half of thunderstorm cloud in the mature stage, especially when the temperatures are between 0° and –25°C. |
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Describe the 9 areas of concern when flying in or near a thunderstorm: Squall Lines
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A squall line is a non-frontal, narrow band of highly active thunderstorms. It generally develops ahead of a cold front in moist and unstable air. It can form rapidly, reaching maximum intensity during the late afternoon or early evening hours. They can range from one to several hundred miles in length, and can be broken or in a continuous line. A squall line can contain extremely severe thunderstorms (with torrential rains, large hail, and tornadoes) and have all the other hazards generally associated with thunderstorms. |
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Describe the 9 areas of concern when flying in or near a thunderstorm: Tornadoes
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Tornadoes occur with isolated thunderstorms at times, but occur much more frequently with supercellular thunderstorms associated with cold fronts and squall lines. Since the vortex extends well up into the cloud, a hidden vortex could be encountered without seeing it.
Tornadoes can occur several kilometres outward from the main area of lightning and precipitation. Cumulonimbus mamma cloud (round shaped underhanging below the cloud base or anvil) is often a signpost to tornadoes and violent turbulence.
Violent turbulence will be generated by a tornado, and an aircraft entering a vortex is certain to suffer structural damage. |
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Describe the 9 areas of concern when flying in or near a thunderstorm: Low Ceilings and Visibilities.
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The visibility is generally near zero within a thunderstorm cloud. The ceiling and visibility also can greatly become reduced in the precipitation between the cloud base and the ground. Heavy precipitation can saturate the air rapidly causing stratus fractus and fog to form rapidly reducing ceilings and visibility turning a VFR approach into an IFR approach. Aircraft will be restricted by these lower ceilings and visibilities but the hazards become manifold when accompanied by other hazards such as turbulence, hail, lightning, and low level wind shear, making precision instrument flying very difficult. |
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Describe the 9 areas of concern when flying in or near a thunderstorm: Heavy rain showers.
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A thunderstorm contains vast amounts of large liquid water droplets (below the freezing level). The heaviest rain showers are associated with the mature stage of development with the onset of the first downdrafts.
Heavy rain showers associated with thunderstorms can cause contamination of the wing surface which results in early stall. If encountered during approach and landing, heavy rain can reduce visibility and cause refraction on the windscreen of the aircraft, producing an illusion that the runway threshold is lower than it actually is.
Water lying on the runway can cause hydroplaning which destroys the braking action of the aircraft. Hydroplaning can also lead to loss of control during take-off. |
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Describe the 9 areas of concern when flying in or near a thunderstorm: Microbursts.
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Microbursts' main effect is to cause sudden and dangerous low level wind shear, causing hazardous conditions for take-off and landing.
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State the meteorological conditions within which an aircraft could encounter icing.
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Dangerous icing can occur in clouds, freezing rain, and freezing drizzle.
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State the clouds in which the heaviest deposits of icing are normally found.
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In winter, stratocumulus clouds will produce the most frequent icing conditions. However, Cumulus (CU), Towering Cumulus (TCU), and Cumulonimbus (CB) clouds will produce the heaviest icing potential.
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State where the most dangerous types of icing are generally encountered.
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As explained earlier in this lesson, the most dangerous types of icing are encountered in dense clouds, composed of heavy accumulations of large supercooled water droplets and in Freezing Rain (FZRA). It is important to note that high Cirrus type clouds are composed of ice crystals. These crystals do not adhere to aircraft. Any cloud at temperatures below freezing will produce some ice. The thicker the cloud the greater the icing potential. |
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Describe how icing can affect the performance of an aircraft.
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-Wings and control surfaces alter the aerodynamic properties of the aircraft airframe, resulting in loss of lift and increased drag. -propellers results in the direct reduction of thrust. -windscreen and canopies is a serious restriction to a pilot’s vision. -PITOT TUBES and STATIC VENTS become clogged with ice, connected instruments such as airspeed indicators and altimeters become inaccurate or inoperative within a few seconds. -Rapid accumulation of ice on RADIO ANTENNAS and MASTS may cause them to vibrate and break. Ice on antennas also reduces communications efficiency. -CARBURETORS and AIR INTAKES become iced, the airflow to the engine is reduced, causing a reduction in power, and in some cases, engine failure. -INTAKE COWLINGS, ROTOR, and STATOR BLADES can result in damage to or failure of TURBINE ENGINES. |
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Describe “ clear air turbulence” (CAT) and state where CAT is normally found.
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-Turbulence in clear air is closely associated with the Jet Stream in a cloudless sky.
-a bumpy turbulent condition that may be severe enough to be a hazard to high performance aircraft. -It occurs at high altitudes (20,000 to 40,000 ft.) -most severe near or just above and below the jet stream core. -CAT is often pronounced with sharply curved jets. Conditions associated with CAT: No clouds. Strong Jet Stream. Rapid change in wind speed over a short distance. Rapid change of wind direction over a short distance. |
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Define Turbulence |
Turbulence is an irregular motion of the air resulting from the formation of eddies or vertical currents in the air.
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List briefly two categories and five causes of turbulence
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Two main types Friction & Thermal each of which can be further divided into multiple types.Turbulence is sometimes difficult to forecast. It often occurs in isolated zones, and always occurs in convective situations. Friction: mechanical, shear and frontal Thermal: daytime convection, cold air convection |
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Describe two categories and 5 causes of turbulence: Friction & it's forces |
Friction is a main type and mechanical, shear and frontal are it's sub types. Mechanical-the result of friction between air + ground. Stability of air, roughness of ground, strength of wind affect its strength and height Loose material is often blown around either restricting or not lifting enough to restrict visibility Shear-result of friction between opposing air currents. occurs when there is a strong wind shear(drastic change in wind direction &/or speed with distance)-There are directional and speed shears Frontal- result of friction between opposing air masses near the frontal surface. turbulence is worst when lifted air is warm, moist and unstable. if thunderstorms develop it will be extremely severe. regularly associated with cold fronts occasionally with warm |
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Describe two categories and 5 causes of turbulence: Thermal & it's forces
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Thermal turbulence is the type and daytime convection and cold air convection are the forces creating it. Daytime convection: result of vertical currents caused by unequal heating of earths surface. affects the strength and extent of convection: stability of air, degree of difference in unequal heating, nature of earths surface, diurnal and seasonal variations in heating. Most common in summer afternoons Cold Air Convection: results when cold air moves over warmer water or land which heats from below causing unstable conditions that favor convection currents and turbulence. stronger contrast between temperatures the more heating and subsequently turbulence |
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What information is included in a METAR? |
Message Type, Sky Cover, Station Indicator, Observation Time, Temperature, Dew Point, Wind, Altimeter, Visibility, Recent weather, RVR, Wind shear, present weather, remarks. |
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What is a METAR? |
-the name of the international meteorological code for an Aviation Routine Weather Report -an internationally coded report used to provide weather information to meet the needs of the user, primarily aviation -there are some national variations for example wind speed is reported in different units |
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What is a SPECI? |
a report taken at other times(opposed to METAR) that reports significant weather events for aviation not previously reported |
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Decode METAR |
1st- code name 2nd- 4 letter ICAO identifier, time of observation or time of significant weather change for SPECI 3rd first three digits are direction to nearest 10 degrees true.(2 minute mean)Next two digits are speed and then the gust and two digit number if applicable to report max gust speeds. If speeds = or > 100three digits are used 4th visibility in statute miles and fractions. Sector visibilites which are half of less are reported as supplement info at end. 5th average runway visual range for a ten minute period reported to nearest hundred feet. if trend changed 300ft or more U or D indicated Upward or Downward. No changes=N. RVR only included if 600ft or less. M preceding lowest value or P preceding the highest indicate an extreme value beyond instrument range 6th- present weather using code table. may have a sign qualifier identifying intensity or proximity, and/or by a 2nd further qualifier 7th-cloud amount of sky covered at and below a specific height reported in 3 digits in hundred of feet. 8th-air temperature and dew point in whole degrees celsius M=negative 9th- Altimeter Setting in hundreth of inches of mercury 10th- recent weather observed since last report but not occuring at time of observation 11th- Remarks in this order: layer type and layer opacity in oktas, general weather remarks and sea level pressure |
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What is a TAF?
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an international meteorological code for an aerodome forecast.
-are in essence, forecast METARS without temperature and pressure that describe the forecast weather broken down into time segments of varying length |
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What is a PIREP? What information does it provide? |
A report of weather conditions encountered by an aircraft in flight. Status(is it urgent?), location, flight level, aircraft flight, plus minimum one other parameter of significance for aviation |
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Pirep Indicators |
UA- Normal PIREP UUA- Urgent PIREP- severe weather elements /OV- location /TM- time of observation /TP- type of aircraft /FL-flight level /SK-sky cover /TA-ambient temperature /WV-wind velocity /TB-turbulence /IC- icing /RM- remarks |
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What is a SIGMET? |
Weather advisory concerning weather significant to safety of aircraft. Limited by international agreement to most serious hazards which are vital to all aircraft. Issues whenever even one phenomena requiring a SIGMET has been reported or is expected within next 4 hours. Volcanic ash should be up to 12 hours where possible. Coverage cannot exceed 4 hours. |
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What phenomena that would require a SIGMET? |
Active thunderstorms, lines of thunderstorms, tropical storms(Hurricances), heavy hail, severe turbulence (not assc with convective cloud), severe icing(not assc with convective cloud), marked mountain waves, widespread sand or dust storms, volcanic ash cloud, low level wind shear, severe squall line, tornado or waterspout, radioactive cloud |
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What is an AIRMET? |
A short term weather advisory intended for aircraft in flight, to notify pilots of potentially hazardous weather conditions not described in the current GFA and not requiring a SIGMET. Is used to amend the GFA for the non occurence of a forecast condition or the occurence of a non-forecast condition significant to aviation. |
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What is GFA? |
Graphic Area Forecast- designed primarily to meet general aviation, and regional air carrier requirements for pre-flight route planning in Canada. |
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When are SIGMETS, AIRMETS, TAFS valid? |
SIGMET- valid for 4 hours then canceled or updated AIRMET- until updated or cancelled or until next regular GFA whichever comes first TAF- broken down into time segments of varying length FD-issued at different times for differing valid period |
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What is an FD? |
Forecast winds and temperatures issued by Canadian Meteorological Centre in Montreal( low level up to 18,000 feet) or US National Weather Service in Suitland(24,000 to 53,000 feet) |
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Symbols of an FD? How are winds more than 100 knots or less than 5 shown? What happens if station elevation is within 1500 feet of predefined forecast altitude? |
dd= direction in true 10degree increments ff=speed in knots +/-= signs of temperature forecast(none at 3000) tt=forecast temperature in wholedegrees celsius -wind less than 5 knots=9900 for direction and speed -wind over 100 knots 100 is subtracted from speed and 500 added to direction -- no wind or temperature is forcasted |
