JX Flashcards
What is the temperature/altimeter error?
11°C / 4% Alt Error
What contains altitude corrections for extreme cold (<0 °C)?
Flight Information Handbook
What is Indicated Altitude?
The altitude as read on the altimeter
What is Absolute Altitude?
Aircraft altitude above the ground (AGL)
You ABSOLUTELY cannot go lower
What is True Altitude?
The altitude referenced to mean sea level (MSL)
What is Pressure Altitude?
The altitude above the standard datum plane
29.92 inHg
What is Density Altitude?
Pressure altitude corrected for non-standard temperature.
Not a height reference, just a performance indicator.
With a pressure change of 1.0 inHg, how many feet will the altimeter change?
1000 feet
Also reffered to as the standard pressure lapse rate (1.0inHG/1000ft)
What is the compostion of pure dry air?
78% Nitrogen
21% Oxygen
1% Other (mixture of 10 gases)
How much of the atmosphere is composed of water vapor?
0 - 5% by volume
What is the height of the troposhere?
28,000 (poles) - 55000 (equator)
36000 (over the states)
Where does nearly all weather occur?
The Troposphere, because its where the most moisture occurs
What marks the boundary called the tropopause?
When there is an abrupt change in the temperature lapse rate.
when temp stops decreasing with alt and remains constant
What is the tropopause?
A transition zone between the tropospere and the stratosphere
Where does the jet stream occur?
Just below the tropopause. A haze layer with a definite top can be seen visually at this layer.
Expect moderate to severe turbulence in the jet stream
Where do contrails form and persist?
The tropopause
because its the coldest area in the lower atmosphere.
What characterizes the stratosphere?
the point above the tropopause in which temperature starts to increase (inversion) to 66000 feet
What is the standard temperature lapse rate?
2 °C/1000 feet
decrease in temp with increase in alt
What is an isothermal lapse rate?
When temp remains constant with increasing altitude
What is an inverted lapse rate?
When temp increases with altitude
What is standard pressure?
29.92 inHg (1013.2mb)
What is standard temperature?
15 °C (59 °F)
What is standard temperature?
15 °C (59 °F)
What interval are millibars drawn at on the surface analysis chart?
4 mb
What are the average jet stream wind speeds?
100-150 knots; sometimes in excess of 250 knots
Which sources reference wind data in TRUE north
Charts and Reports
Which sources reference wind data in MAGNETIC north?
ATIS, Tower, or RSU
Which direction do winds move around a high pressure area?
Clockwise
Which direction do winds move around a low presssure area?
Counter-clockwise
How do winds move in relation to isobars above 2000 feet?
Parallel
Due to the coriolis effect (called gradient winds)
What is the rate of change in a direction perpendicular to the isobars?
Pressure Gradient
What does isobar spacing represent?
Pressure Gradient Force (PGF)
PGF acts perpendicular to the isobars
What does isobar spacing represent?
Pressure Gradient Force (PGF)
PGF acts perpendicular to the isobars
What is the initiating force for all wind?
Pressure Gradient Force (PGF)
Which directions do winds generated by PGF flow at the surface in relation to the isobars?
Perpendicular
Which direction does coriolis move air with regards to its original motion?
Right. Regardless of a High or Low
*northern hemisphere only
What are gradient winds?
The combined effect of PGF and Coriolis Effect
Pressure Gradient Force Circulation
Perpendicular to Isobars
Into Low Pressure
Out of High Pressure
Gradient Wind Circulation Above 2000 AGL
Parallel to Isobars
CCW around Lows
CW around Highs
Surface Wind Circulation Below 2000 AGL
Crossing Isobars at 45°
CCW around and into lows
CW around and out of highs
*created by the balance of friction, reduced coriolis effect, and PGF
Describe the Jet Stream
Narrow band of winds moving at 50 knots or greater
Average height = 30000 MSL
1K-3K miles long
100-400 miles wide
3K-7K feet deep
Flows from WEST to EAST
What are local winds?
Systems of wind associated with a geographic feature (mountain, body of water etc.)
What is dewpoint?
The temperature at which saturation occurs
when mositure becomes visible in air (clouds, fog, precip etc.)
What is Relative Humidity?
The percent of saturation in the air as compared to the maximum it could hold at a given temp
What are the three characteristics of precipitation?
- Showers (cumulus, starts stops rapidly)
- Continuous (stratus, gradual changes/steady)
- Intermittent (cumulus/stratus, stops and starts at least once during the hour)
Forms of precip
Drizzle, Rain, Freezing
Low Clouds
Surface to 6500 AGL
MIddle Clouds
6500 - 20000 AGL
High Clouds
20000 to 40000 AGL
Primarily ice crystals (not an icing hazard)
What makes a cumulonimbus cloud a severe thunderstorm?
When the clous extends past the tropopause
4 methods by which air masses are lifted
- Convergence
- Frontal Lifting
- Orographic Lifting
- Thermal Lifting
Stable Atmosphere
Warm Air Masses
Stratus
Smooth Air
Poor Visibility
Steady Winds/Precip
Rime Icing
Unstable Atmosphere
Cold Air Masses
Cumulus
Rough Air
Good Visibility
Gusty Winds
Showery Precip
Clear Icing
What is an air mass?
A large body of air with uniform TEMP and MOISTURE
How are air masses named?
Moisture content, location, and temperature
they can be hundreds to thousand of sq miles
What is a front?
A boundary between two air masses.
What is a surface front?
The point where a front comes ion conact with the ground
What is a frontal zone?
The area that encompasses the weather on eithe side of the front
How are fronts named?
According to the temperature change after passage
Temp warmer? Warm front
Three Characteristics of Fronts
- Always located in a trough
- Cold fronts move faster than warm
- Passage = 90° shift in winds
What properties are used to classify fronts?
Temperature, Dew Point, Pressure, and Wind
Squall Lines
50-300 mi AHEAD of cold front/roughly parallel
How do winds shift during a COLD front passage?
90° SW to NW
How do winds shift during a WARM front passage?
90° SE to SW