L2 - The atmosphere is a gas Flashcards
What is the mean radius of the Earth?
6,370 km.
What is the mass of the Earth?
6×10 ^24 kg
What is the mean density of the Earth?
5.5 x 10^3 kg m-3
What percentage of the Earth’s surface is covered by oceans?
71%
What is the average depth of the oceans?
4 km
How does the mass of the oceans compare to the atmosphere?
It is 300 times the mass of the atmosphere.
What is the mean density of the oceans?
10 ^3 kgm-3
What is the standard atmospheric temperature range?
273–293 K (0–20°C).
What is the standard atmospheric pressure at sea level?
1013.15 mbar or hPa.
What is the air density at sea level?
1.2 kg m-3
At what height is 90% of the Earth’s atmosphere contained?
below 16 km
What is the scale height?
The vertical distance where air density or pressure decreases by a factor of 1/e≈0.368
What is the lapse rate in the troposphere?
6.5 K/km
Where does the temperature inversion occur in the atmosphere?
at the tropopause
What is the temperature at the stratopause?
260 K
Where is the coldest place in the atmosphere?
The mesopause (T=170K, height = 80 km).
How high does the exosphere extend?
500–1000 km and beyond
What influences the planetary boundary layer?
Surface topography, local winds, and weather.
What is the turbopause?
The region up to 10 km where atmospheric motion causes mixing, maintaining uniform gas composition
What was the primary component of Earth’s primordial atmosphere?
hydrogen
What led to the formation of Earth’s oceans?
Water vapor condensed to form clouds and rain, accumulating surface water
When did oxygen first start forming?
During the evolutionary atmosphere stage (4.0–3.3 BYA) through photosynthesis and photo-dissociation of water.
What process contributed to early oxygen production?
Photosynthesis by cyanobacteria and green plants.
When did current oxygen levels reach?
0.3 BYA.
Where is the maximum concentration of ozone found?
Between 20–40 km altitude (10–12 ppm)
What is the Chapman Mechanism?
A process describing ozone creation and destruction through photolysis of O2
Why is the ozone layer critical for life?
It absorbs soft UV radiation (0.2–0.3 microns).
When and where does the ozone hole form?
Over Antarctica in early spring (Nov–Dec).
What causes the ozone hole?
Chlorine released from manmade CFCs, accelerated by reactions on polar stratospheric clouds (PSCs).
What is the Montreal Protocol?
A 1992 treaty banning CFCs, leading to partial ozone recovery.
When is the ozone hole expected to fully recover?
By 2053, to pre-CFC emission levels.
