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Grade 10 Science - Weather
Weather
Weather: day to day conditions (precipitation, wind, humidity, air pressure, overcast, temperature)
Climate: day to day conditions averaged over may years.
Air Mass: large body of air that has a unique temperature and moisture content
· Temperature: either polar or tropic
· Moisture: either continental or maritime
Precipitation: water that lands on the ground in the form of liquid or solid. Most precipitation originates from clouds.
· Rain: (0.5mm-5mm) coalescence
· Drizzle: (40Mm – 0.5mm) very little coalescence
· Freezing Rain: water freezes when hits the ground
· Wet Snow: crystallization, snow partially melts
· Dry Snow: crystallization, air is cold (stays frozen)
· Sleet: snow melts, then re-freezes into ice pellets
· Hail: cumulonimbus, re-circulation of water droplets that freeze and add more layers as they move up and down into the clouds (only occurs in the summer)
· Dew/Frost: water vapour in the air condenses on objects. The objects must be below the dew point. (For frost, temperature must be below 0oC.
Transfer of Energy
Travels
Travels Through
Examples
Radiation
In the form of waves
Nothing
Sunlight, microwaves, fire
Convection
By the movement of particles
Gas or liquids
A pot of water, pavement giving off heat
Conduction
The vibration of solid particles
A solid
A spoon in hot soup
Heat Sink: an object’s ability to hold heat. Metal is a poor at holding in heat; water holds heat well.
Heat Capacity: a measure of how much energy is required to raise 1kg of a substance by 1oC. It takes 4184J (the measurement of energy) to raise 1kg of water 1oC.
Atmospheric Pressure
The force of gravity exerted on our atmosphere.
The highest pressure is felt would be felt at sea level.
There are pressure gradients all over the Earth due to rising and falling air.
Air always moves from high to low pressure.
High Pressure System
Air moving down
Clear skies
Rotate clockwise
Cold Pressure System
Air moving up
Cloudy/stormy weather
Counter clockwise rotation
Cloud Formation
Water evaporates.
Air rises (with H2O vapour)
Convection clouds or
Orographic clouds or
Frontal clouds
Air cools
Water condenses around particles (cold air is able to hold less water than warm air)
Types of Clouds
Cumulus
“puffy and fluffy” clouds
Heap
Grows vertically (up)
Stratus
flat/ layered clouds
“spread out”
Grows horizontally (out)
Altitude
Low-level → basic names
Mid-lever → alto-
High-level → cirrus-
Contains Precipitation
Nimbostratus or Cumulonimbus
Frontal Systems
Warm Front
Cold Front
Stationary Front
Occluded Front
· Cirrus, then status
· Move slowly
· Light, steady long lasting rain
· Cumulus, cumulonimbus
· Move fast
· Heavy precipitation lasting minutes to hours
· Stable weather
· Eventually warm air will move over cold air
Winds
1. Local Wind
· Caused by regional pressure differences
· Air moves from high pressure to low pressure
· Eg. Wind blowing off the lake toward the land.
2. Prevailing Winds
· Large air masses that move in a general direction depending where you are on the Earth
Prevailing Winds are caused by 2 factors:
a) convection currents
b) the earth’s rotation (east)
c) jet streams: high attitude, fast mobbing, wind (towards the east)
El Nino: Normally, strong trade winds blow from the east along the equator, pushing warm water into the Pacific Ocean.
An El Nino condition results from weakened trade winds in the western Pacific Ocean near Indonesia, allowing piled-up warm water to flow toward South America. During an El Nino year, the surface water temperature and the water level in the Western Pacific become higher than normal. The extra water begins to push eastward, the warm water and air cause thunderstorms and rainfall. These storms move across the Pacific Ocean, eventually reaching the west coast of South America.
Humidity: the amount of water vapour in the air. Warm air can hold more water vapour than cold air. Water molecules have more places to fit in because there are larger space in warm air.
Absolute Humidity: the actual amount of water vapour in the air. (Eg. 15g water/ kg of dry air)
Relative Humidity:
R.H. = actual amount of water vapour in the air x100
maximum amount of water vapour air can hold at a certain temperature
Psychrometer: measures humidity. Dry bulb vs. wet bulb
