Weather Flashcards
DESCRIBE Troposphere
- layer adjacent to earth’s surface
- average height over US is 36,000 ft
- temperature decreases with alt.
- nearly all weather occurs here
- winds generally light but increase with alt.
- winds over 200 kts at top
DESCRIBE Tropopause
- transition zone between troposphere and stratosphere
- isothermal
- jet stream just below
- mod. to sev. turb. from jet stream
- contrails or haze layer persist
- average height of 36,000 ft over US
- anvil tops of Tstorms spread out here
DESCRIBE Stratosphere
- increasing temperature with inc. alt.
- caused by ozone
- generally smooth with exc. vis.
- air is thin
- general lack of weather
DESCRIBE flight conditions of troposphere
- winds light to 200+ kts closer to jet stream
- all weather occurs here
DESCRIBE flight conditions of tropopause
- an infinitely thin region, cannot fly “in”
- jet stream produces mod. to sev. turbulence and wind shear
- haze and contrails persist
DESCRIBE flight conditions of stratosphere
- smooth and exc. vis
- little resistance
- lack of weather
- hard to reach for many planes
DEFINE Lapse Rate
decrease in atmos. temp. with inc. alt.
STATE average lapse rate in dg C
2 dg C
DEFINE atmospheric pressure
pressure exerted on a surface by the atmos. due to the weight of the column of air directly above that surface
STATE standard units of pressure
inches of Mercury (in-Hg or “Hg)
millibars (mb)
DEFINE standard atmosphere
a hypothetical vertical distribution of the atmos. temp., pressure, and density… which by international agreement is considered to be representative of the atmos. for pressure-altimeter calibrations and other purposes
DIFFERENTIATE between sea level and station pressure
SLP is measured from the existing weather if the station were at MSL while station pressure is the atmos. pressure measured directly at an airfield
DEFINE types of altitudes
Altitude: height above a given ref.
Indicated: altitude read directly from the altimeter
Calibrated: indicated corrected for instrument error
MSL/True: actual height above MSL / correcting calibrated for temp. deviations
AGL/absolute: a/c’s height above the terrain directly beneath the a/c
Pressure: height above the standard datum plane
DEFINE Indicated Altitiude
altitude read directly from the altimeter
DESCRIBE effects of pressure changes on aircraft altimeters
High to Low, look out below
Low to High, plenty of sky
DESCRIBE effects of temperature deviations from standard lapse rate on aircraft altimeters
High to Low, look out below
Low to High, plenty of sky
EXPLAIN pressure gradient
rate of pressure change in a direction perpendicular to the isobars
EXPLAIN and IDENTIFY gradient winds and Buys Ballot’s Law (N Hemisphere)
- winds resulting from PGF and Coriolis that circulate CW around highs and CCW around lows
- found above 2,000 ft AGL
- BBL: wind at back, L is to left
EXPLAIN and IDENTIFY surface wind direction (N Hemisphere)
- found below 2,000 ft AGL
- surface friction lessons Coriolis force and winds flow 45 dg across isobars
- 45 dg across isobars and into low in CCW
- 45 dg across isobars and out of high in CW
DESCRIBE jet stream
narrow band of strong winds of 50 kts+ that meanders vertically and horizontally around the hemi. in wave-like patterns
DESCRIBE sea breeze
-during the day, winds that come from the colder sea to warmer land at 15-20 kts
DESCRIBE land breeze
- at night, winds that come from the colder land to warmer sea
- slower than sea breeze
DESCRIBE mountain winds
-at night, winds that come from cooler mountains to warmer valley in circular process
DESCRIBE valley winds
-during the day, winds that come form cooler valleys to warmer mountains in circular process