Mr. Fetch’s Earth Science Classroom

Weather Review 2Definitions

Mr. Fetch’s Earth Science Classroom

Temperature – a measurement of heat Temperature is a factor of particle motion.

Faster moving particles create more heat

Temperature is measured with a thermometer

Mr. Fetch’s Earth Science Classroom

Wind

H L

Wind is moving air

It is caused by differences in air pressure within the atmosphere.

Air under high pressure moves toward areas of low pressure

Mr. Fetch’s Earth Science Classroom

Barometric Pressure

Atmospheric/air pressure is measured with a barometer in units of inches of mercury or millibars

Barometric pressure is the force exerted on objects by the weight of the atmosphere above them.

Mr. Fetch’s Earth Science Classroom

Precipitation:

-Precipitation is rain, sleet or snow, precipitation is any product of the condensation of atmospheric water vapour that falls under gravity

Relative HumidityRelative humidity is a

measure of the amount of water vapor in the air compared to the maximum amount of water vapor the air can hold at that temperature.

A psychrometer is one instrument that measures relative humidity.

Dew Point and HumidexThe dew point is the temperature which

water vapor in air will condense into liquid water. Condensed water is called dew when it forms on a solid surface (like grass) or a cloud when it forms in the sky.

The humidex (short for "humidity index") is a number used to describe how hot the weather feels to the average person. The humidex is a unit-less number based on the dew point, and is equivalent to the dry temperature in degrees Celsius.

The Coriolis Effect• Caused by the Earth’s

rotation• Results in the curving of

moving objects, including air

• It is one thing that causes wind and the direction of prevailing winds that exist in each major latitude belt

Weather Fronts

• The boundary between 2 air masses with different temperatures

• Brings about a change in weather

Prevailing Wind

• The direction the wind blows most of the time in a certain location

MeteorologyIs - the branch of science dealing with weather forecasting.

Atmospheric conditions that are typically measured to provide information for weather forecasts and to study the weather and climate include: temperaturebarometric pressurehumiditywind speed & directionprecipitation

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BarometerDevice used for measuring Atmospheric/air pressure in units of inches of mercury or millibars

Mr. Fetch’s Earth Science Classroom

Short Answers

1. Air Pressure is always changing and depends on factors

such as:• Temperature/Time of day - hotter air has

higher pressure • Altitude – higher up = lower pressure• Humidity – higher = lower pressure• Migrating weather systems – Highs and

Lows

2.Represented on a weather map by

• isobars with an “H” (High Pressure) in the central most isobar

• isobars with an “L” (Low Pressure) in the central most isobar

Highs and Lows on Weather Maps

3.Jet Streams• Narrow currents of fast moving air flowing

in the upper levels of the atmosphere• Flow between cold and warm air masses• Usually move weather systems from place

to place – always WEST to EAST

4. Humidex

The humidex (short for "humidity index") is a number used to describe how hot the weather feels to the average person. The humidex is a unit-less number based on the dew point, and is equivalent to the dry temperature in degrees Celsius.

5. Warm Front

• Along a front the warm air mass will always be forced up as opposed to the cold air mass. Warm air is less dense and therefore will lift more easily than cold air which is more dense.

Cold Front

Passes quickly through an area…sometimes as fast as 100 km/hr

Occluded Front

The Coriolis Effect• Caused by the Earth’s

rotation• Results in the curving of

moving objects, including air

• It is one thing that causes wind and the direction of prevailing winds that exist in each major latitude belt

Mr. Fetch’s Earth Science Classroom

Long Answers

1.What Causes the Weather?Wind, clouds, and precipitation are all the result of the atmosphere responding to uneven heating of the Earth by the Sun.

The uneven heating causes temperature differences, which in turn causes wind, which then moves the heat to a new place.

m

What causes weather?• Caused by the transfer of energy between

these 3 things:- The Sun, Earth’s surface, and the Atmosphere.

• Caused by the transfer of energy between these 3 things:- The Sun, Earth’s surface, and the Atmosphere.

Hot air rises and cools

The sun warms earth’s surface - increasing its temperature.

Water vapor condenses to form clouds & precipitation

The sun’s energy is used to evaporate water and put moisture into the air.

Unequal heating and differences in air pressure cause wind.

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2. Cold Fronts Warm Fronts

CONTRAST

•Created when a cooler air mass overtakes a warmer air mass.•Warm air rises b/c it is pushed up by the cool air and b/c it is less dense.•Steeply sloping curved line front.•Heavy rain and wind.•Passes through quickly.•Cool, dry, and clear skies after•Mainly cumulus type clouds

•Created when warmer air mass overtakes a cooler air mass.•Warm air rises just b/c it is less dense.

•Gentle sloping straight lined front.•Light rain and wind.•Passes through slowly.•Warm, humid, and cloudy after.•Mainly stratus type clouds.

3. Weather from Cold Front

As Approaching

/Front line

•Heavy rain and wind. Passes through Quickly

After Cool, dry, and clear skies after front passes through.

Warm Front

• Created when a warmer air mass slowly overtakes a cooler air mass (Both Traveling in same Direction)

• When the faster moving air meets up with the slower moving cooler air, the warmer (less dense) air rises slowly and gently above the cooler air mass.

• Weather changes slowly. • Creates a gently sloping, straight lined “Front”. • As the warm air rises , it cools, and causes water

vapour to condense.

Warm Front

Passes slowly through an area – a couple of daysAdd

Cold Front

• Created when a fast moving cool air mass rapidly overtakes slower warmer air mass.

• When the faster moving cooler air meets up with the slower moving warm air, the cooler air forces the warm air to rise more quickly than it otherwise would rise.

• Weather changes rapidly. • Creates a steeply sloping, curved “Front”. Almost

verticle.• As the warm air rises , it cools, and causes water

vapour to condense.

Cold Front

Passes quickly through an area…sometimes as fast as 100 km/hr

Stationary Front

• Weather is similar to a warm front but transition is slower and gentler yet.

• When the two masses of air meet, neither has enough force to move the other.

• The two air masses face each other in a “stand off”- they both stop moving.

• Temperature and wind direction are opposite on either side of the front line.

• At the junction of the cold and warm air masses, clouds will form and precipitation will occur.

• Can remain stalled over an area for days.

Stationary Front

Can remain stalled over an area for days

Occluded Front

• A faster moving cold air mass overtakes a slower moving warm air mass.

• A warm air mass gets caught in between two cold air masses.

• The warm air forced up, causing clouds to form. The clouds may result in rain or snow.

Occluded Front

What Causes Wind (Short Answer)Wind is caused by air flowing from high

pressure to low pressure. The Earth's rotation prevents that flow from being direct, but deflects it side to side(right in the Northern Hemisphere and left in the Southern), so wind flows around the high and low pressure areas.

Why do High Pressure Systems cause weather to stay longer? (Short Answer Question)

Because High Pressure systems are large, usually the size of an entire air mass, therefore they take a longer time to move out of an area.

Mr. Fetch’s Earth Science Classroom

Diagram Answers

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Precipitation: Change of State

MELTINGUses Heat

FREEZINGGives off Heat

Sublimation

Uses Heat

Deposition

Gives off Heat

Gives off Heat

Uses Heat

EVAPORATION

CONDENSATION

Freezing/Melting point of water/ice is 00C

+ Add energy

- Subtract energy

Temperature Profile of a Frontal System