Weather...

You can’t see me, but you feel me, you can’t touch me, but I can touch you. I have been called the “Breathe of the Gods”, or the killer and giver of life, gentle and fierce, friendly and enemy, angry and happy. The Native Americans called me Moriah, and Snow Eater (Chinook). The Japanese call me Kaze and in Russia I am called Veter. I can shatter homes, or wake a child from a peaceful sleep or bring relief in times of need. I can spread the most dreaded diseases or bring a welcome freshness. What am I?

Weather is....

The current state of the atmosphere...what is happening right now

Main points to remember as we learn about weather:

The sun warms the earth’s surface and therefore all the air above the surface

The earth is warmed most at the equator and least at the poles---why?

The air above land is warmed more quickly than air above water.

Warm air expands and rises, creating an area of low pressure; cold air is dense and sinks, creating an area of high pressure

Weather Factors

Weather: The state of the atmosphere at a specific time and place

TEMPERATURE= the average motion of molecules↑ TEMP= ↑movement of molecules= feels hot

↓ TEMP= ↓movement of molecules= feels cold

Air Pressure

Warm air= expanding or rising air= leaves behind L pressure

Cold Air=sinking air= leaves an area of H pressure

Wind MovementWind Movement Uneven heating of Uneven heating of

the earth’s surface the earth’s surface causes some areas causes some areas to be warmer than to be warmer than others.others.

As we know, warm As we know, warm always follows cold always follows cold to share it’s warmth- to share it’s warmth- when this happens in when this happens in the atmosphere, the atmosphere, wind happens!wind happens!

What causes winds? A wind is a A wind is a

horizontal horizontal movement of air movement of air from a area of from a area of high pressure to high pressure to an area of low an area of low pressurepressure

It is this It is this difference in difference in pressure that pressure that makes the air makes the air move=windmove=wind

Winds are measured by direction and speed

The anemometer is the tool we use to measure this

Wind chill=↑ cooling the wind causes

Local WindsLocal Winds The land cools and heats faster than the

ocean. Water holds heat longer than land, and takes longer to heat or cool.

SEA BREEZE During the day, the land gets hotter faster than the water. The heated air rises, leaving behind an area of low pressure. Wind from the cooler sea blows in to take the place of that warmer air. These happen during the day!

Land BreezesLand Breezes At night the lands cools off faster

than the sea. Cool air sinks creating an area of high pressure. Wind blows from the land to the sea.

Global Circulation and Global Circulation and Wind SystemsWind Systems

Solar energy is at its Solar energy is at its greatest around the greatest around the equator---Why?equator---Why?

Global Winds:

Wind belts: Horse Latitudes= 30°N and S of

equator =calm winds= worlds desert areas Jet Streams= 10km above the surface blow from the west to the

east

Intense heat = Powerful CONVECTION

Warm, moist air rises and leaves behind an Warm, moist air rises and leaves behind an area of low pressure. This is why most rain area of low pressure. This is why most rain forests are found along equatorial regions.forests are found along equatorial regions.

That air rises until it reaches the top of the That air rises until it reaches the top of the troposphere, where it can’t rise any further. troposphere, where it can’t rise any further.

It spreads out towards the polar regions HOT It spreads out towards the polar regions HOT follows COLD wanting to share its warmth.follows COLD wanting to share its warmth.

As it spreads it begins to cool and sink-As it spreads it begins to cool and sink-usually 30usually 30°N and S of the equator- sinking air °N and S of the equator- sinking air produces an area of H pressure with dry produces an area of H pressure with dry conditions= desert regions on earthconditions= desert regions on earth

Some or the air moves back towards the equator as it sinks...

Tradewinds: Where do you thinkthey got their name?

Who were these winds

particularly important to?

There was an area that sailors There was an area that sailors avoided with their lives...avoided with their lives...

THE DOLDRUMS... THE DOLDRUMS... is the area around is the area around the equator the equator where the wind where the wind completely dies completely dies out... which out... which meant death as meant death as soon as the fresh soon as the fresh water ran out.water ran out.

Water in the Atmosphere: Water in the Atmosphere: HumidityHumidity

HumidityHumidity: measure of the amount of water vapor : measure of the amount of water vapor stuck between molecules in the air. The air’s stuck between molecules in the air. The air’s ability to hold water depends on the air tempability to hold water depends on the air temp

The hotter the air, the more water the air can The hotter the air, the more water the air can holdhold

Cold air: molecules move slower so droplets of Cold air: molecules move slower so droplets of water can start to stick together=water can start to stick together=condensationcondensation

Relative humidityRelative humidity: the amount of water : the amount of water vapor(%) compared to the amount the air can vapor(%) compared to the amount the air can hold- tool used is a hold- tool used is a psychrometer.psychrometer.

100%=air is saturated100%=air is saturated

Cloud Formation

Clouds form when water vapor condenses on dust, salt particles in the air

The temperature in which condensation begins is called the dew point

TYPES OF CLOUDS

Cirrus Clouds: wispy, feathery clouds Form only at high

levels, therefore are made of ice crystals

Types of Clouds

Cumulus Clouds: are puffy white cotton ball looking clouds

Cumulonimbus Clouds

These are thunderstorm clouds

Types of Clouds

Stratus Clouds: clouds that form in flat layers- cover all or most of the sky and are low level clouds

Air masses are masses of air that have the same characteristics of the surface over which it develops

Pressure Systems descending (going down)=H

pressure ascending (going up)=L pressure

Air Masses

Weather Foldable

Warm front Cold front Occluded front Stationary Front

Fronts: the boundary between 2 air masses

Warm Front: warm air slides over departing cold air- large bands of precipitation form

This is the symbol on a map for a warm front

Cold Fronts

Cold air pushes under a warm air mass. Warm air rises quickly=narrow bands of violent storms form

This is the symbol for a cold front

Occluded Front

2 air masses merge and force warm air between them to rise quickly. Strong winds and heavy precipitation will occur

This is the weather map symbol for an occluded front

Stationary Front

Warm or cold front stops moving. Light wind and precipitation may occur across the front boundary

This is the weather map symbol for a stationary front

Reading a weather map

ISOBAR= connects areas of equal pressure BAR comes from BARometric pressure

Reading a weather map...

Isotherm: Connects areas of equal temperature; therm means temperature

Weather Station (not on the TV)