Weather Flashcards
standard day air temp at sea level
15 C or 59 F
standard day air pressure
29.92 Hg (inches of mercury) or 1013 millibars
Absolute Altitude
height above ground level (AGL)
True Altitude
height above mean sea level (MSL)
Density Altitude
altitude relative to the standard atmospheric conditions at which the air density would be equal to the indicated air density at the place of observation- i.e. the altitude at which your aircraft feels like it’s flying
Pressure Altitude
altitude when barometric pressure scale is set to 29.92 Hg
Pressure Altitude= density altitude
during standard conditions
if the density altitude is higher, the air is
thinner
if the density altitude is lower, the air is
more dense
if the density altitude is higher, aircraft performance is
lower
density altitude is affected by 4 factors:
altitude, temperature, atmospheric pressure, humidity
higher density altitude occurs at
higher elevations, higher temperatures, higher humidity, lower atmospheric pressures
lower density altitude occurs at
lower elevations, lower temperatures, lower humidity, higher atmospheric pressures
Low level temperature inversion
an increase in temperature as altitude increases
Open land gives off more rising heat than water or areas of vegetation. This uneven heating of the area creates
convective currents and turbulence
convective currents with turbulent air are experienced at what altitudes and temperatures
low altitudes and warm temperatures
describe how a sea breeze works
land heats up faster than water during the day so warm dense air over land rises and is replaced by cool thin air from over the water
describe how a land breeze works
offshore wind created at night because land cools faster than water so warm dense air over water rises and is replaced by cooler denser air from over the land
wind flows smoothly up a mountain but becomes turbulent when it follows the contour of the mountain down the other side. what is the name for this wind and what does it cause?
katabatic wind, downdrafts
wind shear
sudden drastic change in wind speed and or direction of a small area. can occur at all altitudes in all directions, characterized by 180 degree direction changes and speeds above 50 knots
describe a microburst
short lasting (15 mins or less) small area (1 mile wide, 1000ft vertically) downdrafts of up to 6,000 ft per minute and wind direction changes of 45 degrees or more in seconds
what 4 conditions make the chance of wind shear go up?
around thunderstorms, low-level temperature inversion, frontal zones, clear air turbulence
what are the only two processes in which moisture is added to air
evaporation and sublimation
what factor changes the amount of moisture in the air
temperature
