Whether the Weather- chapter 1 Flashcards
Troposphere:
Altitude
What’s so special about it?
The troposphere is where nearly all weather occurs
large amounts of moisture and increased winds
altitude: 28k-55k AGL (36k AGL over US)
Define:
Atmospheric Pressure
The weight of a column of air directly above an area on the earth’s surface
What are the standard units of pressure measurement?
Standard units of pressure measurement:
inches of Mercury (Hg)
Millibars (mb- this is used internationally)
What is a pressure gradient?
pressure gradient is a change in pressure
Pressure Gradient Force is the pressure exerted on the surfaces of the earth
high pressure is the result of descending air
low pressure is the result of ascending air
*remember: air moves from areas of higher pressure to areas of lower pressure
Define:
Pressure Lapse Rate
what is the standard pressure lapse rate?
Pressure Lapse Rate is the decrease in inches of Hg with an increase in altitude
Standard Pressure Lapse Rate:
1” lost per 1,000’ altitude gained
What is the average temperature lapse rate in degrees Celsius?
2ºC per 1000’ altitude gained
Define:
Standard Atmosphere
Standared Atmosphere:
29.92” Hg
15°C
Temperature Lapse rate: 2C per 1000’f
Pressure lapse rate: 1” Hg/1000’
What is the difference between sea level pressure and station pressure?
Station Pressure is the atmospheric pressure read directly at an airfield or specific altitude,
Sea Level Pressure = station pressure + field elevation
What is Indicated Altitude?
Indicated Altitude is what the altimiter says
What is the effect of pressure change on an altimeter?
A change of 1” Hg will change the altimeter reading by 1,000’
“High to low: Look out Below” means your plane is descending
“Low to High: plenty of Sky”- means your plane is ascending
What are the effects of temperature deviations from the standard lapse rate on the altimeter?
What if its colder than standard conditions?
warmer than standard conditions?
Temperature has a minimal effect on altimeters except at extreme temps.
For completion:
if its colder than the standard atmosphere (15C) the altimeter will indicate a higher altitude
if its warmer than the standard atmosphere, the altimiter will indicate a lower altitude
Define:
Air Mass
An air mass is a large body of air with relatively the same temperature and moisture characteristics across a horizontal plane
Define:
Saturation
Saturation happens when the air can’t hold any more moisture
temperature = dew point
Define:
Dew point temperature and depression
dew point temperature is when air reaches a state where it can hold no more moisture
the dew point “spread” or depression is the difference between temperature and dew point. This means that Saturation happens when the spread is 0.
*As the dew point spread decreases, moisture becomes visible as fog, rain, mist, etc.
Why does atmospheric circulation occur?
Wind Circulation occurs because of the heating and cooling of the earth which leads to ascending and descending air. Top it off with the spinning of the earth (coriolis effect) and you’ve got yourself some circulation
