Weather Ch. 1 Flashcards
1
Q
DESCRIBE the characteristics of the troposphere
A
- Adjacent to earth’s surface
- Average height varies from 55,000 ft over equator to 28,000 ft over poles
- Avg height over U.S. : 36,000 ft
- Pressure systems and seasonal differences casue a variance in height
- Due to heating, the troposphere extends to a greater height in summer than in winter
- Large amounts of moisture and condensation nuclei are found in the troposphere because of its closeness to the Earth’s surface
- nearly all weather occurs here
- Winds are generally light near the Earth’s surface and increase with altitude
- Wind speeds over 200 knots may occur near the top of the troposphere
- The atmosphere becomes less dense with altitude, and roughly 50% of it, by weight, lies below 18,000 feet and 90% within 53,000 feet.
- Temperature generally decreases with altitude increase
2
Q
DESCRIBE the characteristics of the tropopause
A
- Boundry line as thick as paper
- transition zone between the troposphere and the stratosphere
- temperature in this layer is constant with altitude
- strongest winds, those of the jet stream, occur just below the tropopause
- Moderate to severe turbulence is sometimes associated with the wind shear caused by the jet stream
- Contrails frequently form and persist near the tropopause since it is normally the coldest area within the lower atmosphere
- severe thunderstorm tops may penetrate the tropopause into the stratosphere
- the average height of the tropopause over the US is 36,000 feet MSL
- anvil tops of thunderstorms will spread out at the base of the tropopause, and a haze layer with a definite top frequently exists at the tropopause.
3
Q
DESCRIBE the characteristics of the stratosphere
A
- increasing temperature with increasing altitude
- increase in temperature is due to the gas ozone
- Visibility is gucci
4
Q
DESCRIBE the flight conditions associated with the troposphere
A
- majority of weather occurs here
- Winds are light near the surface and worsen with altitude
- Temp and density decrase with altitude
5
Q
DESCRIBE the flight conditions associated with the tropopause
A
- Right above jet stream
- Change in lapse rate
- Frequently find turbulence, contrails, and haze
6
Q
DESCRIBE the flight conditions associated with the stratosphere
A
- generally smooth with excellent visibility
- air is thin and offers very little resistance to the aircraft
- lack of weather in this layer makes for outstanding flying
7
Q
DEFINE a lapse rate, in a classroom
A
- The decrease in atmospheric temperature with increasing altitude
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8
Q
STATE the average lapse rate in degrees Celsius
A
- The average or standard lapse rate is 2° Celsius (3.5° Fahrenheit) per 1000 feet
- The standard lapse rate is actually a shallow lapse rate (between 1.5 and 3.0° C/1000 ft)
- Any lapse rate greater than 3 °C/ 1,000 feet is called a steep lapse rate
9
Q
DEFINE atmospheric (baromertic) pressure
A
- the pressure exerted on a surface by the atmosphere due to the weight of the column of air directly above that surface
- . Pressure, unlike temperature, always decreases with altitude. In the lower layers of the atmosphere pressure decreases much more rapidly than it does at higher altitudes because density decreases as altitude increases
10
Q
STATE the standard units of pressure measurement
A
- inches of mercury (in-Hg) and millibars (mb)
- Inches of mercury is a measure of the height of a column of mercury that can be supported by atmospheric pressure
- millibar is a direct representation of pressure, which is defined as force per unit area
11
Q
DEFINE the standard atmosphere
A
- 29.92 in-Hg (1013.2 mb)
- 15° C (59° F)
- everything is related to standard day conditions at sea level
12
Q
DIFFERENTIATE between sea level pressure and station pressure
A
Station Pressure: Atmospheric pressure at an airfiled or station
Seal Level Pressure (SLP): Pressure at mean sea level (MSL)
- Measured directly at sea level
- calculated if station is not at sea level
- used for surface analysis charts
- STATION PRESSURE CORRECTED FOR ALTITUDE
- If, instead, station pressures were used, the pressure charts would depict the inverse of the land topography
13
Q
DEFINE the types of altitudes
A
- Indicated Altitude: as read on altimeter
- Abosolute Altitude: Above ground level (AGL)
- True Altitude: Above mean sea level (MSL)
- Pressure Altitue: Above Standard datum plane (29.92 in Hg)
- Density Altitude: Not a height reference; the altitude your airplane thinks it is at efficiency-wise. PA correceted for non-standard temp deviations
14
Q
DEFINE indicated altitude
A
- Indicated altitude is the altitude read directly from the altimeter
- For an indicated altitude to be useful, however, the altimeter needs to have the correct reference for the situation by dialing either the local altimeter setting or 29.92 in to the Kollsman window
15
Q
DESCRIBE the effects of pressure changes on aircraft altimeters
A
- Low (pressure) to Hight (pressure) plenty of sky
- MSL= Assigned Altitude + Altitude Error
- AGL= MSL - Field Elevation
- Indicated Altitude on Deck = Field Elevation - Altitude Error
- High (pressure) to low (pressure) look out below
- MSL= Assigned Altitude - Altitude Error
- AGL= MSL - Field Elevation
- Indicated Altitude on Deck= Field Elevation + Altitude Error
