Physics of the Atmosphere Flashcards
What does the atmosphere contain?
Mixture of:
- Gases
- Water Vapour
- Suspended Particles
What forces act on the constituents that make up the atmopshere?
- Expansion of gases as a result of solar heating
- For of gravity holding these constituents in place
What are the functions of the atmosphere?
- Providing oxygen for animal respiration
- Providing CO2 for plant respiration
- Protection against ultra-violet and cosmic radiation
- Propagation of sound waves
- Source of rainwater contributing to water cycle.
What effect maintains the surface temperature of the earth?
Greenhouse effect
What are the layers of the atmosphere and what are their altitudes?
1) Troposphere ( 0 to 26,000 ft/58,000 ft depending on poles or at equator)
2) Stratosphere (Tropopause to 158,000 ft)
3) Mesosphere (158,000 ft –> 290, 000 ft)
4) Thermosphere (290,000 ft –> 700,000 ft)
5) Exosphere ( > 700,000 ft)
What occurs with the weather, temperature and pressure in the troposphere?
- Most weather phenomena occurs in the troposphere
- Temperature decreases at an ISA of -1.98/1000 feet until -56.6 degrees.
- Atmospheric pressure decreases with altitude.
What occurs with temperature in the stratosphere and what causes this?
- Temp remains constant in lower levels, then increases to SL values in upper layers.
- Occurs due to the reaction of UV radiation to create the ozone layer which releases heat.
What is characteristic of the mesosphere?
Rapid decline in temperature to about -113 C at an altitude of 290,000 feet.
What causes heating in the thermosphere and why is there no atmospheric temperature effect?
- Heating is caused by the radiant energy from the sun, with temperatures rising as high as 1500 C.
What is the exosphere regarded as? What type of heating occurs in the exosphere?
- The beginning of true space, where atmospheric gas gradually blends with interplanetary dust and gases.
- Heating is from the radiant energy from the sun.
What is the volumetric composition of the atmospheric gases up to an altitude of 300,000 feet?
Nitrogen (N2) = 78.1%
Oxygen (O2) = 20.9%
Carbon Dioxide (CO2) = 0.03%
Other gases = 0.97%
What is the cause of decompression sickness (DCS) when the body is subjected to decreased atmospheric pressure?
Evolution of Nitrogen out of bodily fluids.
What occurs if too little O2 is given?
Impair the function of the brain and body cells.
What occurs if there is too much O2?
O2 toxicity can result.
What is CO2s role in the atmosphere and the human body?
- Contributes to the greenhouse effect.
- In the human body, CO2 is a by-product and is crucial for control of respiration.
What is the water vapor pressure at 37 C? what is it at 100 degrees?
- 47 mm Hg
- 760 mm Hg (1 atmosphere) at 100 C.
What is pressure, what is its symbol and what is the SI unit?
- Pressure is force per unit area in a direction perpendicular to the surface of an object.
- SI unit is the Pascal (Pa)
- N.m^2
What is atmospheric pressure?
The combined weight of all the gases in the atmosphere.
What is ISA, and what is its purpose?
- ISA is international standard atmosphere.
- It is required as a yardstick to measure all relevant deviations off of.
What are the assumptions of the ISA?
- Air is dry and has a composition as in Table 1-1
- Mean sea level pressure is 1013.25 hPa
- Gravity = 9.8m/sec
- Temperature at mean sea level is 15 C
- Lapse rate is 1.98/1000 feet up to 36,089 feet.
- Tropopause = 36,000 feet.
- Isothermal layer of -56.5 C up to 65, 616 feet
- Temp gradually increases above 65,616 feet
What is atmospheric pressure at 18,000 feet?
1/2 atm
What is atmospheric pressure at 25,000 feet?
1/3 atm
What is atmospheric pressure at 48,000 feet?
1/8 atm
What are the three physiological zones and what are their altitudes?
- Physiological Zone (MSL to 10,000 feet)
- Physiologically Deficient Zone (10,000 to 50,000 feet)
- Space Equivalent Zone (above 50,000 feet)
