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NIFE Weather Review With 100% Correct
Answers
What is the composition of dry air? - correct answers ✔✔78% nitrogen 21% oxygen 1% mixture of 10 other gases How much of the atmosphere, by volume, is composed of water? - correct answers ✔✔0 to 5% What are condensation nuclei? - correct answers ✔✔-Nongaseous substances such as dust and salt particles, pollen, etc -Water molecules condense on these particles and form clouds What layer of the atmosphere is adjacent to the Earth's surface? - correct answers ✔✔Troposphere List some characteristics of the troposphere. - correct answers ✔✔-Adjacent to Earth's surface -Average height of 36,000'MSL above the US -Becomes less dense with altitude -Temperature decreases with increasing altitude -Nearly all weather occurs here -Wind velocity increases with altitude
What is the tropopause and where is it found? - correct answers ✔✔-Transition zone between the troposphere and stratosphere -Temperature is constant with altitude -Jet stream occurs right below (strongest winds) Define Atmospheric Pressure (Barometric Pressure) - correct answers ✔✔-Pressure exerted on a surface by the atmosphere due to the weight of the column of air directly above that surface -Pressure always decreases with altitude (decreases more rapidly at lower altitudes because of decreasing density) What are the two units of measurement for atmospheric pressure? - correct answers ✔✔-in- Hg: measure of the height of a column of mercury that can be supported by atmospheric pressure -Millibar: direct representation of pressure (force/unit area) -Normal sea level pressures range from 28-31 in-Hg (960-1060mb) Surface analysis charts use _______ as the reference pressure level for isobars. - correct answers ✔✔-MSL barometric pressure (to provide a common reference) -Allows meteorologists to track weather systems as they move across the country What type of vertical atmospheric circulation is associated with a high-pressure system? - correct answers ✔✔Air will descend (downward force exerted by high pressure) and diverge, which produces wind
-Standard day conditions at sea level What is the standard lapse rate for pressure and temperature? - correct answers ✔✔-A 1,000' increase in altitude will cause..... Pressure to decrease by 1.0 in-Hg (34mb) Temperature to decrease by 2 deg C (3.57F) What is an isothermal lapse rate and where can it be found? A thermal inversion lapse rate? - correct answers ✔✔-Isothermal: temperature remains the same for different altitudes (tropopause) -Inversion: temperature increases with altitude (stratosphere) What is an air mass? - correct answers ✔✔-A large body of air that has essentially uniform temperature and moisture conditions in a horizontal plane -No abrupt temperature/dew point changes at a given altitude -Named according to their location, moisture content, and temperature What are the temperature classifications of air masses? - correct answers ✔✔Warm and Cold What are the moisture content classifications of air masses - correct answers ✔✔Maritime and Continental What are the location classifications of air masses? - correct answers ✔✔Tropical Arctic Polar Equatorial
The ______ of an air mass indicates its stability. - correct answers ✔✔-Temperature -Warm air masses bring stable conditions -Cold air masses are unstable What is the saturation point of air defined as? What is the relationship between saturation point and temperature? - correct answers ✔✔-When it contains the maximum amount of water vapor that it can hold for that temperature -As air temperature increases, it can hold more water What is Dew Point Temperature? - correct answers ✔✔-Temperature at which saturation occurs -Representation of the amount of moisture in the air -The higher the dew point, the greater chances for clouds, fog, or precipitation What is Dew Point Depression/Spread? - correct answers ✔✔-Difference between the air temperature and dew point temperature -When dew point depression is 4F (2C) or less, the air is holding close to the maximum amount of water vapor possible. Can Dew Point ever be greater than ambient air temperature? - correct answers ✔✔-No -Dew point is equal to or less than Air Temp What is relative humidity? - correct answers ✔✔-Percent of saturation of the air -Air can become saturated if....
- it is cooled, which lowers the dew point depression
- evaporation occurs, adding moisture to the atmosphere
What is density altitude? - correct answers ✔✔-Pressure altitude corrected for nonstandard temperature deviations -NOT a height reference; it is a measure of engine performance -Higher temperature = Lower air density = HIGHER Density Altitude = DECREASED PERFORMANCE Moisture affects aircraft in a similar manner as temperature but to a lesser degree On a day hotter than a standard day at sea level, what is the effect on air density, density altitude, thrust, lift, and takeoff/landing performance - correct answers ✔✔Air Density: decreases Density altitude: increases Thrust: decreases Lift: decreases Takeoff/landing performance: decreases If, while flying at a constant indicated altitude, sea level pressure decreases, what happens to the column of air aloft that you are flying in? - correct answers ✔✔The whole column aloft is lowered When flying from high pressure to low pressure, what altitude will your altimeter indicate, and what will happen to your actual MSL altitude? - correct answers ✔✔Altimeter will indicate higher altitude than actual MSL altitude will be lower than indicated When flying from low pressure to high pressure, what altitude will your altimeter indicate, and what will happen to your actual MSL altitude? - correct answers ✔✔Altimeter will indicate lower altitude than actual MSL altitude will be higher than indicated
When flying to an area with a higher temperature, what altitude will your altimeter indicate, and what will happen to your actual MSL altitude? - correct answers ✔✔Altimeter will indicate lower altitude than actual MSL altitude will be higher than indicated When flying to an area with a lower temperature, what altitude will your altimeter indicate, and what will happen to your actual MSL altitude? - correct answers ✔✔Altimeter will indicate higher altitude than actual MSL altitude will be lower than indicated How are winds reported? - correct answers ✔✔The direction from which it is blowing (Wind blows from a particular direction) On a Surface Analysis Chart, isobars are drawn with a _______ mb interval spacing. - correct answers ✔✔Four How does air move around a high-pressure and low-pressure system? - correct answers ✔✔Clockwise around high and out of the system Counter around low and into the system Gradient winds are found at what altitude and how do they flow with respect to the PGF? - correct answers ✔✔-Above 2000' AGL and perpendicular to the PGF -Parallel to isobars Surface Winds are found at what altitude and how do they flow with respect to the PGF? - correct answers ✔✔-Below 2000' AGL and at a 45 degree angle across isobars -Coriolis Force attempts to turn the air as it flows; however, surface friction reduces the speed of the wind and only allows the CF to rotate it 45 degrees
Clouds may be defined as ___________. - correct answers ✔✔-The visible manifestation of weather -The most important element in the formation of clouds is water vapor Describe how clouds form - correct answers ✔✔-Clouds form when air becomes saturated either by 1) being cooled to dew point or 2) the addition of moisture -Most clouds form from some lifting process followed by atmospheric cooling -Water vapor condenses on condensation nuclei How are clouds classified? - correct answers ✔✔According to their appearance, form, and altitude of their bases What is the altitude of Low Clouds? - correct answers ✔✔Surface to 6500' AGL What is the altitude of Middle Clouds? - correct answers ✔✔6500' to 20,000' AGL What is the altitude of High Clouds? - correct answers ✔✔Above 20,000' AGL Special clouds are _________ - correct answers ✔✔Clouds with extensive vertical development What part of a cloud determines its classification based on altitude? - correct answers ✔✔Cloud base What is the general description of cumuliform clouds? - correct answers ✔✔Lumpy, billowy clouds with a definite pattern/structure
What is the general description of stratiform clouds? - correct answers ✔✔Uniform base, formed in horizontal, sheet-like layers What are the characteristics of low clouds? - correct answers ✔✔-Bases range from surface to 6,500'AGL -Mainly composed of water droplets -Most serious hazard is proximity to the ground -Hide terrain and thunderstorms -Possible icing -No to moderate turbulence -Light rain/drizzle -Visibility is a few feet (Nimbo/nimbus clouds will produce violent/heavy precipitation) What are the characteristics of Middle Clouds? - correct answers ✔✔-Bases between 6,500' and 20,000'AGL -Have the prefix alto (light) -Composed of ice crystals, water droplets, or a mix -Visibility from a few feet to 0.5 miles -Possible turbulence -Icing is common -Rain, rain and snow, or snow is possible -Virga (precip evaporates before reaching ground) What are the characteristics of High clouds? - correct answers ✔✔-Bases average 20,000 to 40,000'AGL -Prefix cirro or cirrus
Stable: Stratiform Describe the three types of atmospheric stability. - correct answers ✔✔-Neutrally stable: air is lifted and remains in place after lifting action is removed -Stable: air is lifted and returns to original position after lifting action is removed -Unstable: air is lifted and continues to rise (free convection) after the lifting action is removed What are some "signs in the sky" that indicate stable air? - correct answers ✔✔Temperature inversions, low fog, and stratus clouds What are some "signs in the sky" that indicate unstable air? - correct answers ✔✔Thunderstorms, showers, towering clouds, dust devils, and rapidly decreasing air temperature while climbing What is a front? - correct answers ✔✔-An area of discontinuity that forms between two contrasting air masses when they are adjacent to each other -A border, a boundary, or line between two air masses -Sufficiently different temperature and moisture properties What is the surface front? - correct answers ✔✔-Point where a front comes in contact with the ground -Line that is plotted on surface analysis charts with different colors and shapes representing each type of front What is the frontal zone? - correct answers ✔✔-The area that encompasses the weather located on either side of the front -Most active weather is focused along and on either side of the surface front and frontal zone -Abrupt changes indicate that the frontal zone is narrow and vice versa
What happens to the characteristics of each air mass at a front as altitude increases? - correct answers ✔✔-At 15,000 to 20,000', the differences between two air masses become negligible and cloud and precipitation patterns are not easily attributable to one frontal type or another -Temperature contrast between air masses can extend as high as tropopause How are fronts named? - correct answers ✔✔According to the temperature change that they bring Every front is located in a ______ of __________ pressure - correct answers ✔✔Trough; low Warm/Cold fronts produce a __________ shift in winds. - correct answers ✔✔90 degree Which type of front generally moves faster? - correct answers ✔✔Cold Front (20knots) How fast does a warm front move? - correct answers ✔✔Approximately 10-15 knots In what general direction does a warm front move? - correct answers ✔✔To the northeast In what general direction does a cold front move? - correct answers ✔✔To the southeast What is a frontal discontinuity? - correct answers ✔✔-Differences in the various properties of adjacent air masses -Temperature, dew point, winds, and pressure With respect to a cold front, a warm front will have a __________ dew point. - correct answers ✔✔-Higher
What is a Squall Line? - correct answers ✔✔-Line of violent thunderstorms 50-300 miles ahead of a cold front and roughly parallel to it -Dashes and double-dotted red line on a chart -Impossible to fly through -Wind shift from SW to NW What are the characteristics of a Warm Front? - correct answers ✔✔-Boundary of advancing warmer, less dense air riding up and over a cold air mass -Creates a broad area of cloudiness 500-700 miles in front of the front -Slower speed and gradual slope -Wind shifts from SE to SW (not as sudden) -Common to see stratiform clouds, steady precipitation that gradually increases -Low stratus and fog (poor visibility; 300-900 foot ceilings) -Little to no turbulence except embedded thdrstrms -Wide area of potential icing (due to shallow slope) -Drizzle, freezing drizzle, rain, freezing rain, sleet, and snow are all possible What are the characteristics of a Stationary Front? - correct answers ✔✔-Frontal border that shows little or no movement -Neither air mass is replacing the other -Alternating warm and cold front symbols opposing one another (in red and blue) -180 degree wind shift -Weather conditions are similar to a warm front but less severe What are the characteristics of an occluded front? - correct answers ✔✔-Form when a faster moving cold front overtakes a slower moving warm front
-Two types: warm or cold occluded front depends on which front remains in contact with the ground -Both W and C symbols pointing in the same direction (purple) -180 degree wind shift -Weather will be a combination of both fronts Characteristics of an inactive front - correct answers ✔✔-Clouds and precipitation do not accompany inactive fronts -Reason for showing them is to indicate the boundary of opposing air masses and it displays the location of potentially unfavorable flying weather What is turbulence? - correct answers ✔✔-Any irregular or disturbed flow in the atmosphere producing gusts and or eddies -Turbulence intensity is on a subjective scale What are the types of turbulence? - correct answers ✔✔-Classified according to causative factors
- Thermal
- Mechanical
- Frontal
- Large-scale wind shear What is Clear Air Turbulence? - correct answers ✔✔-Turbulence in the absence of or outside of clouds -Most common above 15,000'MSL -Most severe CAT is associated with the jet streams
-Moist, unstable warm air produce the strongest vertical currents -Most severe frontal turbulence associated with fast moving cold fronts Describe Wind Shear turbulence - correct answers ✔✔-Large-scale wind shear turbulence results from a steep gradient in wind velocity and direction producing eddy currents -Greater the change in wind speed and/or direction in a given area, the more severe the turbulence will be How can a temperature inversion cause wind shear turbulence? - correct answers ✔✔- Inversions can cause turbulence at the boundary between cold calm air near the surface, and faster moving warm air above -The boundary can cause turbulent eddies, which on takeoff or landing, could produce wind shear and turn a headwind into a tailwind (vice versa for landing) How does the Jet Stream produce turbulence? - correct answers ✔✔-Rapid change of wind speed within a short distance of the jet core can be significant -Vertical shear is generally close to the same intensity both above and below -Horizontal shear is stronger on the cold side than on the warmer side -Slowest winds (relatively) on the outside and increase in velocity as you move to the core What are the recommended flight techniques for turbulence? - correct answers ✔✔1)Establish and maintain thrust settings consistent with turbulent air penetration. DO NOT CHASE AIRSPEED 2)Trim the aircraft for level flight at turbulent air penetration speed. DO NOT CHANGE THE TRIM
- Reference gyro indicator for pitch and bank. DO NOT MAKE ABRUPT CONTROL INPUTS 4)DON'T CHASE THE ALTIMETER What are the two categories of aircraft icing? - correct answers ✔✔1) Structural: Forms on external structure (wings, fuselage, antennas, pitot tubes, rotor blades, and propellers); can cause control problems and performance degradation
-Clear, rime, mixed, or frost
- Engine icing: ice forms on the induction or compressor sections of an engine, reducing its performance (as high as +10C) What are the two requirements for icing to form? - correct answers ✔✔1) Super-cooled water droplets must be in the atmosphere
- Aircraft's surface temperature must be below freezing -Icing is possible in any cloud when temperature is 0C or below Describe clear icing - correct answers ✔✔-Forms between 0 and -10C -Large water droplets due to unstable air (cumulus) -Water droplets move along with the airflow, freeze gradually, and form a solid layer of ice -Builds fast, can freeze flight controls, and disrupts airflow over the wings Describe rime icing - correct answers ✔✔-Milky white in appearance -Occurs between -10 and -20C -Lighter, softer, and less transparent than clear ice -Occurs in stable conditions (stratiform clouds) -Brittle and fairly easy to break off -Protrudes forward into the air stream along the leading edge of airfoils Describe mixed icing - correct answers ✔✔-Combination of clear and rime ice -Occurs at temperatures form -8 to -15C -Lumpy like rime ice but also hard and dense like clear ice
