1- Atmosphere Flashcards
(25 cards)
Atmosphere definition:
“the gaseous envelope surrounding a celestial body”
In the case of the earth, it is held together by gravity
4 most common gases and percentages:
Nitrogen 78%, Oxygen 21%, Argon 0.95%, Carbon Dioxide 0.05%
name the other gases found in the atmosphere in small amounts
(trace gases - as they come in a small quantity):
carbon monoxide, helium, methane, ozone, hydrogen
What is a very important trace gas pilots need to know about:
water vapour
Despite its small quantity in atmosphere, it has the greatest effect on the weather. Without water vapour, we wouldn’t have weather.
2 examples of Solid-state of water vapour:
hail and snow
2 examples of Liquid state of water vapour:
clouds and rain
Till how many km above the earth does the composition of gases stay relatively constant?
Then what happens?
1) 60km above earth
2) gravitational separation alters the composition of the atmosphere
Layers in order of nearest to furthest from the Earth:
Troposphere - Stratosphere - Mesosphere
what property is used to structure the atmosphere in various segments and layers?
Temperature
Name the properties of the Troposphere
> as you go higher there is a drop in air temp
> because of gravity, this layer contains more than 70% of the total mass of the atmosphere
What is the tropopause?
The tropopause is the upper boundary of the troposphere where the temp no longer drops with altitude increasing
The thickness of the Troposphere and therefore the height of the Tropopause varies depending on where in the Earth you are.
Why is this?
The reason for this is the surface temperature: warmest/highest - coldest/lowest
give the approximate height of the tropopause in the following:
Poles
Equator
Average (@45 degrees)
Poles - the height of tropopause about 8km
Equator - about 16km
Average - 11km/36,090ft @ 45 degrees latitude
Where in the world is the Troposphere temp the lowest and highers and at what temp?
why?
1) Lowest at the Equator: about -80 degrees
Highest at the Poles: about -40 degrees
2)Why?
Knowing that the troposphere temperature decreases with height = the further away the tropopause is, the colder the air temp is
The tropopause signifies the limit of most weather and significant cloud development.
Why is that?
The tropopause is where temp no longer drops with height which causes air to be stable (limits vertical movement of air). The lack of any vertical airflow prevents cloud and weather development
Where is the stratosphere found?
50km above the earth
Name 2 characteristics of the Stratosphere?
> characterised by the lack of any significant change of temp with height
stratosphere stops when temp begins to drop (to negative) with height again
Remembering the graph shown in the video, there is an S shape in temp within this layer - why?
presence of ozone gas
What does ISA stand for?
International Standard Atmosphere
When was the ISA made and by who?
but whats a limitation of their model?
the ICAO in 1994
only went up to 32km above the earth
State the ISA for temperature, density, and pressure at sea level
Temp: 15 degrees C
Pressure: 1013.25 hPa
Density: 1.225 kg/m^3
What does MSL stand for?
Mean Sea Level
Why is it so important to know how to find the ISA deviation?
It is used a lot in aviation and meteorology, especially when considering aircraft performance and error corrections for instruments.
Example: there is an airfield 1000ft above sea level. the actual temp is 20 degrees, what is the ISA deviation?
A: knowing that at MSL the temperature is 15 degrees but also falls by 2 degrees every 1000ft up, we can say that the ISA is 13 degrees. The difference between the actual temp and ISA temp is 7 degrees.
The deviation is said in this form: it is 7 degrees warmer than ISA and this is shown by “ISA +7”
