WeatherWeather

The condition of air on earth at any given The condition of air on earth at any given time or place- whether its warm or cold, time or place- whether its warm or cold, dry or wet, blowing or calm. dry or wet, blowing or calm.

Weather starts with the sun. The sun’s heat Weather starts with the sun. The sun’s heat warms our atmosphere and causes two warms our atmosphere and causes two things to happen:things to happen:

1.1. Water evaporates into the airWater evaporates into the air2.2. Air risesAir rises

Predictable Patterns of Weather Predictable Patterns of Weather continued…continued…

Precipitation:Precipitation: depends on the temperatures of the ground depends on the temperatures of the ground and atmosphere.and atmosphere.

Wind speed and direction:Wind speed and direction: help determine unequal help determine unequal heating or air masses, and is also related to air pressure heating or air masses, and is also related to air pressure differences.differences.

Temperature:Temperature: Affected by many factors Affected by many factors

Cloud Cover:Cloud Cover: caused by pressure systems and can caused by pressure systems and can change precipitation and temperature.change precipitation and temperature.

Weather Smart: Forecasting and Weather Instruments   (United Streaming)   (United Streaming)

Weather and Climate Facts:Weather and Climate Facts:

Weather and climate are usually related to: rain, Weather and climate are usually related to: rain, clouds, storms, wind and temperature.clouds, storms, wind and temperature.

Water is the main factor (water on Earth are Water is the main factor (water on Earth are constantly interacting, changing and moving)constantly interacting, changing and moving)

Clouds also play and very important role when Clouds also play and very important role when talking about humidity, wind, temperature, talking about humidity, wind, temperature, geography and precipitation. They can also be geography and precipitation. They can also be linked to specific weather conditions.linked to specific weather conditions.

Climate patterns: help determine types of Climate patterns: help determine types of weather in different regions. weather in different regions.

Review: Water CycleReview: Water Cycle

Evaporation: Evaporation:   Evaporation is when the sun heats up   Evaporation is when the sun heats up water in rivers or lakes or the ocean and turns it water in rivers or lakes or the ocean and turns it into vapor or steam. The water vapor or steam into vapor or steam. The water vapor or steam leaves the river, lake or ocean and goes into the leaves the river, lake or ocean and goes into the air. air.

Condensation:Condensation:    Water vapor in the air gets cold and changes     Water vapor in the air gets cold and changes back into liquid, forming clouds. This is called back into liquid, forming clouds. This is called condensation. condensation.

You can see the same sort of thing at home... pour a glass of You can see the same sort of thing at home... pour a glass of cold water on a hot day and watch what happens.  Water cold water on a hot day and watch what happens.  Water forms on the outside of the glass.  That water didn't forms on the outside of the glass.  That water didn't somehow leak through the glass!  It actually came from somehow leak through the glass!  It actually came from the air.  Water vapor in the warm air, turns back into liquid the air.  Water vapor in the warm air, turns back into liquid when it touches the cold glass. when it touches the cold glass.

Precipitation: Precipitation:  Precipitation occurs when so Precipitation occurs when so much water has condensed that the air much water has condensed that the air cannot hold it anymore.  The clouds get cannot hold it anymore.  The clouds get heavy and water falls back to the earth in heavy and water falls back to the earth in the form of rain, hail, sleet or snow. the form of rain, hail, sleet or snow.

Groundwater/Runoff:Groundwater/Runoff: When the precipitation When the precipitation falls to the ground and is either soaked into falls to the ground and is either soaked into the ground or runs off into rivers, oceans or the ground or runs off into rivers, oceans or lakes. lakes.

Weather Smart: The Water Cycle and Clouds

Water Cycle Songs (Tune of She’ll be Coming Around the Mountain)

(Song to the tune of , It’s Raining, It’s Pouring.)

ITS RAINING, ITS POURINGTHE OCEANS ARE STORING, WATER FROM THE FALLING RAINWHILE THINDERCLOUDS ARE ROARING

THE RAIN NOW IS STOPPINGTHE RAIN’S NO LONGER DROPPINGSUN COMES OUT AND SOAKS UP WATER LIKE A MOP THAT’S MOPPING

THE WATER’S STILL THEE NOWBUT HIDDEN IN THE AIR NOWIN THE CLOUDS IT MAKES A HOMEUNTIL THIERE’S RAIN TO SHARE NOW

REASONS FOR SEASONS REASONS FOR SEASONS THE EARTH IS TITLED ON AN AXIS AT THE NORTH AND THE EARTH IS TITLED ON AN AXIS AT THE NORTH AND

SOUTH POLE AND THIS CREATES THE SEASONS. SOUTH POLE AND THIS CREATES THE SEASONS.

THE IMAGINARY LINE RUNNING THROUGH THE MIDDLE OF THE IMAGINARY LINE RUNNING THROUGH THE MIDDLE OF THE EARTH IS CALLE D THE THE EARTH IS CALLE D THE EARTH’S AXIS/EQUATOR.EARTH’S AXIS/EQUATOR.

ANOTHER REASON WE HAVE DIFFERENT SEASONS IS ANOTHER REASON WE HAVE DIFFERENT SEASONS IS BECAUSE THE EARTH MOVES AROUND THE SUN SO THE BECAUSE THE EARTH MOVES AROUND THE SUN SO THE NORTH POLE IS EITHER FACING TOWARD THE SUN OR AWAY NORTH POLE IS EITHER FACING TOWARD THE SUN OR AWAY FROM THE SUN. FROM THE SUN.

THE EARTH’S TILT CAUSES DIFFERENT AMOUNT OF THE EARTH’S TILT CAUSES DIFFERENT AMOUNT OF SUNLIGHT TO REACH THE EARTH AT DIFFERENT TIMES IN SUNLIGHT TO REACH THE EARTH AT DIFFERENT TIMES IN THE YEAR. THE NORTHERN HEMISPHERE GETS MORE THE YEAR. THE NORTHERN HEMISPHERE GETS MORE DIRECT SUNLIGHT IN THE SUMMER BECAUSE THE SOUTERN DIRECT SUNLIGHT IN THE SUMMER BECAUSE THE SOUTERN HEMSPHERE IS TITLTED AWAY FROM THE SUN THEY ARE HEMSPHERE IS TITLTED AWAY FROM THE SUN THEY ARE HAVING THEIR WINTER.HAVING THEIR WINTER.

NEAR THE EQUATOR, THE EARTH DOESN’T HAVE WINTER NEAR THE EQUATOR, THE EARTH DOESN’T HAVE WINTER OR SUMMER. THE WEATHER BARELY CHANGES AT ALL.OR SUMMER. THE WEATHER BARELY CHANGES AT ALL.

REVOLUTION AND ROTATIONREVOLUTION AND ROTATION

REVOLUTIONREVOLUTION: EARTH MOVING IN A PATH : EARTH MOVING IN A PATH AROUND THE SUN, RESULTING IN ONE AROUND THE SUN, RESULTING IN ONE EARTH YEAR.EARTH YEAR.

ROTATIONROTATION: THE EARTH SPINNING AROUND : THE EARTH SPINNING AROUND EVERY 24 HOURS, RESULTING IN DAY AND EVERY 24 HOURS, RESULTING IN DAY AND NIGHT.NIGHT.

Weather and GeographyWeather and Geography

There are many geography factors that There are many geography factors that affect weather and climate. They include:affect weather and climate. They include:

1.1. LatitudeLatitude

2.2. AltitudeAltitude

3.3. WindsWinds

4.4. Distance from the seaDistance from the sea

5.5. Urbanization/living in the cityUrbanization/living in the city

Latitude:Latitude: The distance from the equator can The distance from the equator can determine weather and climate.determine weather and climate.

As you move closer to As you move closer to the equator the the equator the temperature temperature increases. The farther increases. The farther away you are from the away you are from the equator the equator the temperature temperature decreases. This is due decreases. This is due to the sun’s rays.to the sun’s rays.

Earth has three major climate zones. These zones are determined by latitude, or their position on Earth in relation to the equator

Altitude:Altitude: The farther up you go the temperature The farther up you go the temperature decreases and it gets cold. Air is less dense and decreases and it gets cold. Air is less dense and

cannot hold the heat.cannot hold the heat.

Notice that there is Notice that there is snow at the top of snow at the top of this mountain. The this mountain. The higher up you go higher up you go the colder it the colder it becomes. becomes. Therefore, Therefore, mountain regions mountain regions have colder have colder temperatures.temperatures.

•

Distance from the sea and bodies of water:Distance from the sea and bodies of water: The closer The closer you are to the ocean the cooler the temperature.you are to the ocean the cooler the temperature.

Water warms and cools much more SLOWLY than land.The temperature of water does NOT change as quickly as the temperature on land does.Land near water has milder weather because of the water’s influence

.That’s why cities like That’s why cities like

Wilmington have cooler Wilmington have cooler temperatures then cities temperatures then cities

like Raleigh.like Raleigh.

Bodies of Water

Lakes help moderate the temperatures on the land The nearby water causes an increase in

moisture in the air, so in the winter these areas experience heavy snowfall.

Lake Effect Snow

Urbanization: Urbanization: Living near or in a city also affect the temperature.

Cities usually have Cities usually have warmer and warmer and rainier weather rainier weather because it is because it is surrounded by surrounded by pavement , larger pavement , larger building and building and factories.factories.

Winds:Winds: Depending of where the winds came from, they Depending of where the winds came from, they can increase or decrease temperature. Example: If cold can increase or decrease temperature. Example: If cold

winds blow, especially from the north, temperature is winds blow, especially from the north, temperature is colder. If warm winds blow, usually from the south, the colder. If warm winds blow, usually from the south, the

temperature is warmer.temperature is warmer.

When wind blows against a mountain it causes the air to rise and cool. When it flows over the mountain and down the other side it causes the air to become cooler and takes the moisture from the clouds to create rain. This is called the rain shadow effect

CloudsClouds

Clouds consist of billons of tiny water Clouds consist of billons of tiny water droplets (and even ice crystals) floating in droplets (and even ice crystals) floating in the sky and clouds form when rising air the sky and clouds form when rising air cools and the moisture in it condenses to cools and the moisture in it condenses to water droplets. water droplets.

Three things are needed for clouds Three things are needed for clouds to form: evaportation, cooling, and to form: evaportation, cooling, and

condensationcondensation

Clouds can be named by their appearance Clouds can be named by their appearance or how they look and where they are or how they look and where they are located in the sky.located in the sky.

Types of CloudsTypes of Clouds Cirrus:Cirrus: clouds are high, thin, and clouds are high, thin, and

wispy white clouds that are made wispy white clouds that are made of tiny ice pieces and they bring of tiny ice pieces and they bring change in the weather.change in the weather.

Stratus:Stratus: are low, flat gray clouds are low, flat gray clouds which are layered. when stratus which are layered. when stratus clouds are low to the ground, it clouds are low to the ground, it creates fog. These clouds usually creates fog. These clouds usually mean rain is coming. .mean rain is coming. .

Cumulus: Cumulus: are white, puffy , clouds are white, puffy , clouds

that look like cauliflower and make that look like cauliflower and make fair weather on sunny days. fair weather on sunny days.

Cumulonimbus: Cumulonimbus: thunderheads thunderheads clouds are huge, puffy, dark clouds are huge, puffy, dark clouds, means heavy rain.clouds, means heavy rain.

Altitude and Cloud Formation

Clouds can also be described by the altitude/height at which they form. Clouds that form at high altitudes are described by the prefix cirro. So stratus clouds that form high in the sky are called cirrostratus.

Clouds that form in the middle of the sky are described by the prefix alto. A stratus cloud that forms at a middle altitude is called an altostratus cloud.

Alto cumulus alto stratus

Clouds that form at low altitudes or low in the sky are described by the prefix strato so a cumulus cloud that forms at a low altitude is called a stratocumulus cloud.

Nimbostratus

Guess the Clouds

These clouds form when the wind is strongThese clouds form when the wind is strong

CIRRUSCIRRUS

Brings fair weather

CumulusCumulus

Brings thunderstorms

CUMULONIMBUSCUMULONIMBUS

Another word for fog

STRATUSSTRATUS

Predictable Patterns of WeatherPredictable Patterns of Weather

HIGHHIGH pressure: pressure: cooler temperatures and cooler temperatures and less moisture.less moisture.

LOWLOW pressure: pressure: hotter temperatures and hotter temperatures and more moisturemore moisture

Air Mass

A large body of air that has the same temperature and level of humidity throughout.

cool air masses: where the land temperature is cool

warm air masses: form over the land that is warm.

dry air masses: form over dry areas

wet air masses: form over wet areas like oceans.

Fronts

When air masses meet, a boundary called a front is formed, preventing the masses from mixing.

Fronts

Two different types of air masses do not mix, because of the different densities

Warm is less dense than cold air.

When warm air and cold air meet, warm air will rise above cold air.

Cold Front Cold Front: What is it? At the cold front, the cold air

cuts underneath the warm air and forces the warm air up a much steeper angle. At cold fonts the air is cooled quickly and forms a narrow band of thick cumulonimbus

clouds. These produce heavy rain, snow or precipitation.

Cold Fronts bring:

Heavy rains Thunderstorms Sometimes snow

Warm Front

A warm air mass moves up and over a cold air mass.

Warm Fronts Bring:

Rainy, drizzly weather

Often followed by clear, warm weather

Occluded Front

Two cold air masses move toward each other, warmer air between is pushed up

Occluded Fronts Bring:

Cool temperatures

Plenty of rain

and snow

Stationary Front

When a warm and cold air mass meets, but neither has enough energy to push against each other

Stationary Fronts Bring:

Many days of overcast, rainy weather

Cold Front: A cold air mass moves under a warm air mass & pushes the warm air upward. .Cold fronts bring heavy rain and thunderstorms and cold weather.

Warm front: forms when warm air bumps with colder air. This front brings rainy, drizzly weather, often followed by warm, clear weather

.

Occluded front: forms when a warm air mass is caught between two cold air masses. This brings cool temperatures and lots of rain and snow.

Stationary front: occurs when a warm air mass and a cold air mass meet.. This brings many days of overcast and rainy weather.

Breezes affect the weather too

Valley breeze: The Sun warms the air above the valley during the day. The warm air rises and flows up the mountain.

Mountain breeze: At night the mountains cool down faster than the valleys do because of their elevation. The cool air sinks and flows down the mountain.

Sea breeze: The cool, high-pressure air over the ocean that flows toward land

Land Breeze: the movement of air created by cool air over land moving toward the ocean.

Sea Breeze

During the day, air over the ocean is cool. Cool air masses form over areas of high pressure. Air over the land is warmer, and as it rises, it creates an area of low pressure. The cool, high pressure air over the ocean

now flows toward the land, creating a sea breeze.

Sea Breeze

Land Breeze

At night, the air over the ocean is warmer than the air over the land. (WHY?)

The warm air over the ocean rises creating an area of low pressure. The cool air over the land forms an area of

high pressure and moves toward the ocean, producing a land breeze.

Land Breeze

Mountain Breeze

At night, the mountains cool down faster than the valleys do, because of their elevation.

The cool air SINKS and flows down the mountain, causing a mountain breeze.

Mountains affect:

Patterns of Rainfall Rain Shadow Effect

Wet Side

Dry

Side

Which breeze am I?

Sea Breeze

Land Breeze

Mountain Breeze

Valley Breeze

Air Pressure and Barometers

Temperature affects air pressure. Lighter, warm air creates low air pressure Heavier, cold air creates high pressure.

Barometers measure air pressure. If air pressure changes, it means the

weather is probably going to change, too.

Barometric Pressure

Although air feels as if it weighs nothing it actually weighs a lot.

Air pressure is the weight of the air pressing against everything on Earth.

Barometers measure air pressure.

Pictures of Barometers

Rising Barometric Pressure

If the air pressure changes from low to high pressure, the barometric pressure is rising.

The weather will probably be nice and clear.

Falling Barometric Pressure

If the barometric pressure changes from high to low pressure, it is falling.

This means a storm might be coming.

Other Weather Tools that help Predict the Weather

Anemometer measures wind speed.

Thermometer measures temperature outside.

Rain Gauge measures the amount of rain fall.

Hygrometer measures the amount of humidity or moisture is in the air

Wind Vane: measures wind direction

Rain: Warm Air and Cold Air Meeting Forms Rain

Cool air sinks and forms an area of high pressure.

Warm Air Rising Above a Cold Front: Warm air rises and creates

an area of low pressure.

Jet Streams Jet streams are narrow bands of fast moving air

about eight miles above the Earth's surface. They are among the most powerful forces on the

planet. Jet streams affect surface weather. Wind is the movement of air from a high

pressure area to a low pressure area. Winds curve because of Earth's rotation. In the temperate zone, warm and cold air clash

along weather fronts.

Jet Streams

Global Wind Patterns As equatorial areas are heated most, the air above

them warms and rises as it becomes lighter than the surrounding air, causing an area of low pressure.

In cooler areas, the air sinks because it is heavier and results in an area of high pressure. Winds will blow as air is squashed out by the sinking cold air and drawn in under the rising warm air.

Any difference in temperature like this will always cause a difference in air pressure – and therefore winds will blow.

A good expression to remember is that: “Winds blow from high to low" (ie: from high pressure to low pressure).

So if you know the temperature and pressure in different areas, you will always be able to predict the wind direction.

Coriolis Effect

Winds do not simply blow in straight lines from north to south. Instead, they are bent by the spinning of the Earth: To the right north of the equator, and to the left in the south.

The Coriolis Effect bends every wind on Earth, resulting in a distinct pattern of winds around the world

Trade Winds and Westerly Winds

Trade Winds: Blow mainly from the east; for example the steady winds blowing towards the equator from the subtropics.

These are known as trade winds because they were used by sailing ships carrying trading goods around the world.

Westerly Winds is a wind systems blowing from the west and moving the winds to the east

The Doldrums

The Doldrums are an area of low pressure occurring where the trade winds meet along the equator. Winds here are usually calm or very light and so ships would avoid the area because they would only be pushed along very slowly.

Wind Chill Temperature is the main factor affecting

how warm or cold you are. However, wind can also play an important role, making you feel colder than you would otherwise be.

This is because the wind causes your body to lose heat faster.

The higher the wind speed, the more heat is lost from your body and you therefore feel colder.

The temperature your body feels as a result of the wind is called the wind chill temperature.

Cold AirCold air is heavier than warm air.Cold air puts more pressure on

the planet.A cold air area is called “high

pressure.”

Warm AirWarm air is lighter than cold air.Warm air puts less pressure on

the planet.An area of warm air is called “low

pressure.”

Low Pressure- air circulation

Low Pressure – Storm caused by rising warm, moist air

High Pressure – air circulation

High Pressure – Sunny

Why is bad weather usually associated with low pressure and good weather

with high pressure? In an area of low pressure, air from neighboring areas

(which are of higher pressure) moves in. It has nowhere to go but up. Upward movement of air causes condensation of water vapor, leading to the development of cloud and rain. So, a low pressure area usually associated with bad weather.

In contrast, in an area of high pressure, the air at low levels spreads outward and air descends from aloft. Downward motion warms up the air and is favorable for evaporation. Hence, a high pressure area usually has fine and dry weather. Air descends in high pressure area and rises in low pressure area.

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