Download WEATHER WATCH STUDY NOTES HP LP

Grade 5
SCIENCE
Name: ____________________________
WEATHER WATCH
STUDY NOTES
Weather - The condition of the atmosphere with respect to heat/cold,
wetness/dryness, clearness/ cloudiness for a period of time.
Weather changes over time and from place to place.
Three things necessary for weather are Heat, Air, Moisture (HAM)
Weather takes place in the Troposphere (The lower part of the atmosphere).
Climate – the long-term weather pattern of an area, including temperature,
precipitation, and wind.
Meteorology – The study of weather.
Meteorologists use lots of instruments to
study weather and make predictions.
Temperature – The amount of heat in a substance
and is measured by a thermometer.
Measured in degrees of Centigrade (Celsius). An
example is 10°C or -15°C.
Convection current – the movement of air or water due to heating and cooling.
Warm air rises (lighter) and falls when it cool down (heavier).
The ceiling is usually warmer.
(That’s why
smoke rises
and, in a fire,
you should
crawl on the
floor to get
away from it)
The floor is usually cooler.
Air moves to take the shape of whatever container it is in. Air can stretch out
(expand) or squeeze in (compress)
Air can have different pressures.
Nature doesn’t like to leave empty spaces (no air).
Air moves from areas of high pressure (thick, heavy,
gas molecules squeezed together) to low pressure
(thin, light, gas molecules spread out)
HP
LP
(The arrow is wind)
A barometer measures air pressure.
When air pressure is high there is not
much room between molecules for
water so weather is usually fair
High pressure = fair weather
When air pressure is low there is room
between molecules for water so weather
is usually rainy
Low pressure = rainy
When air pressure drops it means weather is getting worse. Some animals can feel
the pressure dropping and act different. That fact causes lot of old weather sayings:
Air pressures are often shown on weather maps as “H” and “L”. These make warm
and cool “fronts”. A front is a moving mass of air.
When a warm front and
a cool front run in to
each other, the warm,
moist front usually gets
pushed up on top of the
heavier cool front. This
rises the warm moist air
up into the sky where it
cools down and forms
clouds.
When warm air rises it leaves a low pressure and other air moves in to replace it.
Solids heat faster than liquids.
Land heats faster than the ocean.
Sea Breeze – cool air blowing from the sea on to the shore
During a hot
summer day, the
air over the land
is warmer than
the air over the
ocean. The
warm 'land air'
rises and cooler
'ocean air'
moves to the
shore
Solids lose heat faster the liquids.
Land cools down faster than the ocean (Water keeps heat longer than land).
Land Breeze - cool air blowing from the land out to sea
In the evening
after a hot
summer day the
land cools
quickly.
As the ocean
slowly releases its
warmth the air
over the ocean
warms and rises.
Cooler “land air’
moves out to sea
to fill in the
space
Water cycle - The evaporation of water from a body of water into the air (as water
vapour gas), the condensation of this moisture into precipitation and its collection
back to a large body of water.
Evaporate – When a liquid turns into
a gas.
Condense – When a gas turns into a
liquid by cooling.
Example: 1. tiny drops of water on
outside of glass of cold water.
2. Dew drops on grass in the
morning.
Humidity - The measure of the amount of moisture in the air. Can be measured with
a psychrometer or with a hygrometer. It is measured in % which means
“out of 100”.
A day with 5 % humidity would be hot and dry.
A day with 100 % humidity would be foggy or rainy.
Human hair reacts to the humidity in the air (flat or frizzy).
Dew Point - The temperature at which the water vapor in air condenses out into
droplets of water forming precipitation.
Warmer air can hold more moisture.
For instance: a day that is 28ºC would be more humid than a day that is 1ºC if there
is water nearby (a desert is hot but dry because there is no water nearby).
Warm air soaks up water vapour like a sponge.
Clouds - A mass of minute water droplets or ice crystal. Clouds form when a mass of
warm moist air moves into an area with lower air pressure. The air expands and
cools and the water vapour condenses.
Four main types
Cirrus
Found high in the sky.
Thin, wispy, feathery looking.
Made of tiny ice crystals in the
sky.
A change in the weather will
often follow.
Often a sun halo.
Stratus
Form near the Earth’s surface.
Means relative humidity near the
ground is high.
Usually flat clouds that cover
large parts of the sky.
Means stormy weather coming.
Fog is a very low form.
Cumulus Most often seen in summer.
Thick, fluffy, white and have flat
bases. (bunches of white
cotton).
Sign of fair weather.
Nimbus
Dark, dense and low, Sky usually
all dark colour due to large
amount of moisture.
They almost always mean rain or
thunder showers.
Notice how different clouds are at different heights.
Cumulonimbus causes big storms and lightning.
Precipitation - The name for moisture that falls out of clouds. Temperature changes
what it is.
Rain –liquid water.
Sleet (freezing rain)- falls as rain and freezes near ground.
Hail – ice built up as layers (like an onion).
Snow – water frozen as crystals.
Wind is measured by strength and direction.
anemometer – an instrument for measuring the speed of the wind in km/h
Wind vane – measures the direction wind is coming from. (points on a compass: N,
NE, E, SE, S, SW, W, NW)
Wind occurs when air naturally tries to balance high pressure areas and low
pressure areas. HP always moves to LP.
There are many types of storms and severe weather: Thunderstorms, Blizzards,
Tornado, Hurricanes, Drought (long time with no water), Flood, Heat Wave…
Specific events must happen for storms to occur.