Weather

WeatherWeatherhttp://content.blackgold.ca/ict/Divison2/Weather.ppthttp://content.blackgold.ca/ict/Divison2/Weather.ppt

What is Weather?What is Weather?

• WeatherWeather is the condition of the Earth’s is the condition of the Earth’s Atmosphere at a given time.Atmosphere at a given time.

• It can change drastically in a 24 hour period.It can change drastically in a 24 hour period.

What causes Weather?What causes Weather?

• All elements of weather are the All elements of weather are the direct result of energy from the sun. direct result of energy from the sun.

• The sun’s rays hit Earth and the land The sun’s rays hit Earth and the land absorbs the heat unevenly. absorbs the heat unevenly.

• This uneven heating causes changes This uneven heating causes changes in weather.in weather.

What does weather include?What does weather include?

• Air temperatureAir temperature

• Cloud coverCloud cover

• Amount of sunlightAmount of sunlight

• Relative humidityRelative humidity

• PrecipitationPrecipitation

• Wind speedWind speed

• Wind directionWind direction

TemperatureTemperature

• TemperatureTemperature is the average kinetic is the average kinetic energy of the particles in a substance. energy of the particles in a substance.

• Expressed in degrees Fahrenheit or CelsiusExpressed in degrees Fahrenheit or Celsius

• Temperature is measured by an Temperature is measured by an instrument called a instrument called a thermometerthermometer..

The Earth’s AtmosphereThe Earth’s Atmosphere

• It is a layer of It is a layer of gases that gases that surrounds the surrounds the earth.earth.

• It is made up It is made up mostly of nitrogen, mostly of nitrogen, carbon dioxide and carbon dioxide and oxygen.oxygen.

A Bunch of Hot Air.A Bunch of Hot Air.

• Cold air contracts or sinks.Cold air contracts or sinks.

• The air molecules get closer together, The air molecules get closer together, which makes the air heavier or more which makes the air heavier or more dense.dense.

• Hot air expands or rises. The molecules Hot air expands or rises. The molecules get further apart, become less dense and get further apart, become less dense and they get lighter.they get lighter.

Convection Current Convection Current • Is the act of a fluid transferring heat Is the act of a fluid transferring heat

energy.energy.

WindWind

• Wind is moving air in the atmosphere.Wind is moving air in the atmosphere.

• Air is always moving from high pressure Air is always moving from high pressure to low pressure.to low pressure.– High pressure is caused by descending airHigh pressure is caused by descending air– High P air driesHigh P air dries

• The strongest winds are tornadoes, the The strongest winds are tornadoes, the air pressure is extremely low.air pressure is extremely low.

How to measure wind speedHow to measure wind speed• Wind speed is Wind speed is

measured with an measured with an anemometer.anemometer.

•Wind Direction is always stated in terms of where the wind is coming from.

Measuring Wind DirectionMeasuring Wind Direction

• Wind SockWind Sock

• WeathervaneWeathervane

Beaufort ScaleBeaufort Scale

• The The Beaufort scaleBeaufort scale is an empirical is an empirical measure for describing measure for describing wind intensity based mainly on observed sea based mainly on observed sea conditions. Its full name is the conditions. Its full name is the Beaufort wind force scaleBeaufort wind force scale. .

Humidity- Moisture in the Humidity- Moisture in the AirAir• The sun heats up water and causes The sun heats up water and causes

evaporation.evaporation.• The moisture in the air is called The moisture in the air is called

humidity.humidity.• Saturated is when the air cannot hold Saturated is when the air cannot hold

any more moisture.any more moisture.

The Water CycleThe Water Cycle

The Water CycleThe Water Cycle

• The sun heats up the water- The sun heats up the water- evaporationevaporation

• The water vapor (gas) The water vapor (gas) condensescondenses into into cloudsclouds

• The clouds become saturated and The clouds become saturated and precipitationprecipitation is the result. is the result.

• The precipitation pools in lakes, oceans The precipitation pools in lakes, oceans and rivers. Evaporation happens again.and rivers. Evaporation happens again.

Relative HumidityRelative Humidity

• Ratio of how much moisture is in the Ratio of how much moisture is in the air and how much the air can hold.air and how much the air can hold.– Warm air can hold more waterWarm air can hold more water

• 50% humidity means the air is 50% humidity means the air is holding 50% of the moisture it holding 50% of the moisture it COULD hold COULD hold

PrecipitationPrecipitation

• When there is too much moisture, the water When there is too much moisture, the water will fall as precipitation. will fall as precipitation.

• Precipitation will fall in rain or snow Precipitation will fall in rain or snow depending on the temperature of the air depending on the temperature of the air through which the moisture falls. through which the moisture falls.

• Other forms of precipitation are sleet and Other forms of precipitation are sleet and hail.hail.

Forms of PrecipitationForms of Precipitation

SnowSnow

• If the air is cooled If the air is cooled below the freezing below the freezing point of water, the point of water, the condensing moisture condensing moisture is quickly freeze into is quickly freeze into ice crystals.ice crystals.

• The ice crystals join The ice crystals join to make snowflakesto make snowflakes

• Snowflakes are Snowflakes are always six sided.always six sided.

RainRain

• When droplets of When droplets of moisture join moisture join together becoming together becoming heavy enough to heavy enough to fall to the ground.fall to the ground.

HailHail

• Formed in Formed in cumulonimbus cumulonimbus (storm) clouds. (storm) clouds. They are frozen They are frozen droplets of droplets of moisture.moisture.

• Form as water falls, Form as water falls, then rises several then rises several times in the cloudtimes in the cloud

SleetSleet

• When falling rain When falling rain starts off in warmer starts off in warmer air, but passes air, but passes through air below through air below freezing, the rain freezing, the rain cools and freezes cools and freezes onto surfaces when onto surfaces when it hits the ground.it hits the ground.

Facts on PrecipitationFacts on Precipitation

• It takes approximately 10 It takes approximately 10 centimetres of snow to make one centimetres of snow to make one centimetre of rain. centimetre of rain.

• Dew happens when moisture in the Dew happens when moisture in the air cools off at night. air cools off at night.

• In colder temperatures, dew is frost.In colder temperatures, dew is frost.

Air PressureAir Pressure

• The force that is applied on everything on The force that is applied on everything on the Earth caused by the weight of the air.the Earth caused by the weight of the air.

• Air particles are mobile, they exert Air particles are mobile, they exert pressure on objects. pressure on objects.

• High air pressure brings warm, dry air. High air pressure brings warm, dry air. Low air pressure brings rain or moistureLow air pressure brings rain or moisture

Air PressureAir Pressure

• Air pressure can change quickly, for Air pressure can change quickly, for example when a storm comes in. example when a storm comes in.

• There are three factors that affect air There are three factors that affect air pressure: altitude, air mass pressure: altitude, air mass temperature and the amount of temperature and the amount of moisture in the air.moisture in the air.

• A Barometer is used to measure air A Barometer is used to measure air pressure.pressure.

CloudsClouds

• Clouds come in many shapes and forms.Clouds come in many shapes and forms.

• Some are high in the sky, while others are Some are high in the sky, while others are so low they touch the ground. so low they touch the ground.

• No matter what shape or elevation, clouds No matter what shape or elevation, clouds form the same way, by having water vapor form the same way, by having water vapor condense onto small solid particles like condense onto small solid particles like dust, sea salt, and pollution dust, sea salt, and pollution

Types of CloudsTypes of Clouds

• There are There are Four Four main types of cloudsmain types of clouds

• Cirrus-Cirrus- found high in the atmosphere found high in the atmosphere

• Cumulus-Cumulus- found in mid-atmosphere found in mid-atmosphere

• Stratus-Stratus- found in the low atmosphere found in the low atmosphere

• Nimbus-Nimbus- storm clouds. storm clouds.

CirrusCirrus

• They are thin, They are thin, wispy clouds blown wispy clouds blown by high winds into by high winds into long streamers.long streamers.

• They usually mean They usually mean fair to pleasant fair to pleasant weather. weather.

CumulusCumulus

• They are puffy They are puffy clouds that clouds that sometimes look like sometimes look like pieces of floating pieces of floating cotton cotton

• They can develop They can develop into a into a cumulonimbus, cumulonimbus, which is a which is a thunderstorm cloud thunderstorm cloud

StratusStratus• uniform grayish uniform grayish

clouds that often clouds that often cover the entire sky.cover the entire sky.

• They resemble fog They resemble fog that does not reach that does not reach the ground. the ground.

• Usually no Usually no precipitation falls precipitation falls from stratus clouds, from stratus clouds, but sometimes they but sometimes they may drizzle. may drizzle.

Nimbus (Cumulonimbus)Nimbus (Cumulonimbus)

• Thunderstorm clouds Thunderstorm clouds that form if cumulus that form if cumulus clouds continue to clouds continue to grow vertically. grow vertically.

• Lightning, thunder, Lightning, thunder, and even violent and even violent tornadoes are tornadoes are associated with the associated with the cumulonimbus. cumulonimbus.

SeasonsSeasons

• The Earth orbits The Earth orbits around the sun.around the sun.

• The Earth tilts on its The Earth tilts on its axis 23.5 degrees.axis 23.5 degrees.

• The area of the The area of the Earth, that heats up Earth, that heats up more, is aimed more, is aimed toward the sun.toward the sun.

SeasonsSeasons• When Canada is When Canada is

tilted away from the tilted away from the sun, it is winter. sun, it is winter.

• When Canada is When Canada is tilted towards the tilted towards the sun, it is summer.sun, it is summer.

• Spring and Autumn Spring and Autumn are in between.are in between.

DaylightDaylight

• The Earth turns on its axis, one complete The Earth turns on its axis, one complete rotation in one day. (24 hours)rotation in one day. (24 hours)

• The Sun rises in the east and sets in the The Sun rises in the east and sets in the westwest

• The amount of daylight is related to the The amount of daylight is related to the Earth’s orbit around the sun (tilt of Earth).Earth’s orbit around the sun (tilt of Earth).

Factors that influence weather Factors that influence weather in different areas.in different areas.

• Land ElevationLand Elevation

• Location- latitude (and longitude)Location- latitude (and longitude)

• The sunThe sun

• Cloud coverCloud cover

• Air pressureAir pressure

• Earth’s orbit (seasons)Earth’s orbit (seasons)