The Atmosphere Flashcards
What is the atmosphere?
The layer of air surrounding the Earth
The atmosphere is made up of gases that are necessary for what?
- Acting as a screen and blocking out the dangerous rays from the sun (UV rays)
- Ensuring a stable climate on Earth by retaining heat
- Cellular respiration (oxygen)
- Photosynthesis (CO2)
- Water vapour
Why does air exert pressure?
Because it contains particles that are colliding with one another
What determines atmospheric pressure?
Particles colliding with each other.
The more collisions, the higher the atmospheric pressure
Atmospheric pressure is measured using what?
Barometer
Atmospheric pressure depends on what?
The height of a place above sea level and decreases with increase in altitude.
At higher altitude, the density and temperature of the air are what? Why?
Lower
The number of collisions between molecules are lower and thus the pressure is lower
When the temperature rises, what do air particles do? Consequence?
Air particles move away from one another so the density decreases in that specific area
When the temperature decreases, what do air particles do? Consequence?
Air particles move closer together so the density increases in that specific area
What temperature of air sinks?
Rises?
Why?
- Cold air sinks because it is heavier than warm air (particles move closer together so density increases)
- Hot air rises because it is lighter than cold air (particles move away from one another so the density decreases in that specific area)
Describe convection
Air rises above the warm humid regions at the equator (low pressure zones), heads towards the poles and then sinks over cold, dry regions (high pressure zones)
At the same time, as the Earth rotates, the cold polar air makes its way to the equator
What are air masses?
Large regions of the atmosphere with uniform temperature and humidity.
They can change the weather due to winds.
What is a front?
The place where two air masses meet
What happens when two air masses meet (how does the air move)?
The denser cold air slides beneath the lighter warm air
Describe a warm front.
A warm air mass moving into a cold mass
Describe a cold front.
A cold air mass moving into a warm mass
What happens to the moisture in the air as it cools when fronts meet?
It forms clouds
Is a warm front a low or high pressure system?
Low-pressure (because hot air rises)
When does a warm front form? Describe what happens.
When a mass of warm air moves towards a mass of cold air.
The warm air rises over the cold air and creates HEAVY, stratified clouds resulting in cloudy weather and light, scattered showers
-> Associated with clouds and precipitation (bad weather)
When does a cold front form? Describe what happens.
Occurs when a mass of cold air (high-pressure) meets a mass of warm air (low-pressure)
The warm air rises rapidly and in a steep slope over the cold air, and then cools
-> Normally associated with dry weather and mostly clear skies with fluffy clouds
(enough moisture/temperature contrast = thunderstorm)
Describe depressions.
- Air gets warm, particles move away from one another and the air mass becomes less dense
- The air mass becomes lighter and rises, leaving an empty space under it. This is called a depression. The space becomes an area of low pressure.
- Rising air encourages cloud formation and often results in precipitation.
Describe anticyclones.
- When air sinks, the pressure rises
- The air density then increases and the mass of air becomes heavier, and sinks toward the ground creating an area of high pressure. This area is called an anti-cyclone (H on weather charts)
- Cold air, sinking does not favour cloud formation so this phenomena results in clear skies and stable weather
Strong depressions form where? What is this called?
Often form over warm waters of tropical oceans. A huge spiral with heavy winds then forms.
This is called cyclone/hurricane/typhoon
What is the greenhouse effect?
A natural process that allows the Earth to keep some of the heat it receives from the sun.
