Earth's Atmosphere Flashcards
(30 cards)
What is the composition of the Earth’s atmosphere?
78% nitrogen, 21% oxygen, 0-3% water vapour, 0.03% carbon dioxide, 0.000003% ozone.
Water vapour has the greatest impact on climate.
What are the important physical properties of the atmosphere?
Pressure, temperature, humidity, radiation.
Air has inertia, fluidity, and viscosity.
What is the lowest layer of the Earth’s atmosphere?
Troposphere.
Extends from the ground to 60,000 ft at the equator and to 35,000 ft at the poles.
What separates the troposphere from the stratosphere?
Tropopause.
What does the International Civil Aviation Organization (ICAO) Standard Atmosphere (ISA) define?
Standardized conditions at latitude 40° N and height of 70,000 ft.
Includes MSL pressure, temperature, lapse rate, height, and temperature of the tropopause.
What is the MSL pressure in the ICAO Standard Atmosphere?
1013.2 hPa or mb or 29.92” Hg.
What is the lapse rate in the troposphere according to the ISA?
1.98° C per 1,000 ft.
What is air density?
The weight of air per cubic foot.
What does mobility refer to in the context of air?
The tendency of air to move when influenced by various forces.
What happens to air when it is compressed?
It becomes heavier and has greater density.
What is atmospheric pressure?
The force per unit area exerted by the weight of air at a specific level.
How is atmospheric pressure measured?
By a barometer in millibars (mb) /hectopascals (hPa) or in inch of mercury (inHg)
What is station pressure?
The actual atmospheric pressure at the elevation of a particular station.
What is sea level pressure used for?
As a standard to compare station pressures and for weather chart construction.
What characterizes a HIGH or ANTI-CYCLONE?
Atmospheric pressure increases towards the centre. High pressure system has descending air rotating clockwise and gently flowing outwards in the northern hemisphere.
What is a LOW or CYCLONE?
Atmospheric pressure decreases towards the centre. Air is rising and rotating counterclockwise with strong inward flow in the northern hemisphere. Air is converging and ascending!
How do highs and lows circulate in the northern hemisphere?
Highs circulate clockwise, lows counterclockwise.
What is a TROUGH in meteorological terms?
An elongated area of low pressure.
What is a RIDGE?
An elongated area of high pressure.
What is a COL?
A neutral area between highs and lows.
According to Buys Ballot’s Rule, where will the region of lower pressure lie if you stand with your back to the wind?
To your left.
What happens to pressure levels in warm air compared to cold air?
Pressure levels will be higher in warm air and lower in cold air.
How do pressure levels compare over the poles versus the Equator?
Pressure levels will be lower over the poles than over the Equator.
What are isobars?
Isobars are lines of equal MSL pressure drawn on weather charts.
