WeatherWeather

What is Weather?What is Weather?

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

• It is different than It is different than climateclimate, which is the conditions of a region , which is the conditions of a region over many years.over many years.

• It takes place in the troposphere.It takes place in the troposphere.

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

• The atmosphere is heated mainly by The atmosphere is heated mainly by the energy that is radiated back up the energy that is radiated back up from the Earth’s surface.from the Earth’s surface.

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 amount of heat in a is amount of heat in a substance. Expressed in degrees substance. Expressed in degrees Fahrenheit or Centigrade (Celsius)Fahrenheit or Centigrade (Celsius)

• The temperature of a region is affected by The temperature of a region is affected by latitude and the altitude.latitude and the altitude.

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

The Earth’s AtmosphereThe Earth’s Atmosphere

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

• It is made up of many It is made up of many gases. gases. – 78% Nitrogen78% Nitrogen– 21% Oxygen21% Oxygen– < 1%-Carbon < 1%-Carbon

Dioxide,Water vapor Dioxide,Water vapor and other greenhouse and other greenhouse gases.gases.

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 and molecules begin to interact dense and molecules begin to interact with eachother and heat up.with eachother and heat up.

• 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.

Familiar???? (yep, convection currents!)Familiar???? (yep, convection currents!)

Air CirculationAir Circulation

• Since warm air rises, the upper part Since warm air rises, the upper part of the room is the warmest. The of the room is the warmest. The coolest part of the room would be coolest part of the room would be closer to the floor.closer to the floor.

• As gases spread out and their As gases spread out and their volume increases, their temperature volume increases, their temperature decrease.decrease.– What kind of relationship is this????What kind of relationship is this????

Convection Currents Convection Currents

• Is the act of a cold fluid or gas pushing a Is the act of a cold fluid or gas pushing a warmer, more dense fluid or gas out of the warmer, more dense fluid or gas out of the way.way.

WindWind

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

• Air is always moving from high Air is always moving from high pressure to low pressure.pressure to low pressure.

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

How to measure wind speedHow to measure wind speed

• Wind speed is Wind speed is measure using a measure using a device called an device called an anemometer.anemometer.

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

Humidity- Moisture in the Humidity- Moisture in the AirAir• The sun heats up the water on land The sun heats up the water on land

and causes evaporation.and causes evaporation.• The moisture that is in the air is The moisture that is in the air is

called humidity.called humidity.• Saturated is when the air has too Saturated is when the air has too

much moisture and cannot hold much moisture and cannot hold anymore.anymore.

Relative HumidityRelative Humidity

• It is the ratio of how much moisture It is the ratio of how much moisture is in the air and how much the air is in the air and how much the air can hold.can hold.

• 50% humidity means the air is 50% humidity means the air is holding 50% moisture holding 50% moisture

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 two main forms: rain Precipitation will fall in two main forms: rain or snow depending on the temperature of or snow depending on the temperature of the air through which the moisture will fall. the air through which the moisture will fall.

• 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.

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 drops cool and drops cool and freeze onto freeze onto surfaces when they surfaces when they hit the ground.hit the ground.

Facts on PrecipitationFacts on Precipitation

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

• Dew is moisture in the air cools off at Dew is moisture in the air cools off at night. In the morning it is found on night. In the morning it is found on everything. In colder temperatures, everything. In colder temperatures, dew is frost.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, ie- Air pressure can change quickly, ie- when a storm comes in. 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

CloudsClouds

• Clouds serve several important functions.Clouds serve several important functions.

• They provide rain and snow. They provide rain and snow.

• They also help retain heat, so it doesn’t They also help retain heat, so it doesn’t escape quickly back into space. escape quickly back into space.

• On hot days, clouds provide shade On hot days, clouds provide shade

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

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

StratusStratus

• are uniform grayish are uniform grayish clouds that often cover clouds that often cover the entire sky.the entire sky.

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

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

Nimbus (Cumulonimbus)Nimbus (Cumulonimbus)

• They are thunderstorm They are thunderstorm clouds that form if clouds that form if cumulus clouds cumulus clouds continue to grow continue to grow vertically. vertically.

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

Can you identify these Can you identify these clouds?clouds?

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 closer to more, is closer to the sun.the sun.

SeasonsSeasons

• When we are tilted When we are tilted away from the sun, away from the sun, it is winter. it is winter.

• When we are tilted When we are tilted towards the sun, it towards the sun, it is summer.is summer.

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

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

• Land ElevationLand Elevation

• Location- lattitude and longitudeLocation- lattitude and longitude

• The sunThe sun

• Cloud coverCloud cover

• Air pressureAir pressure

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