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?
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: The state of the atmosphere at a specific time and place
the average motion of molecules
↑ TEMP= ↑ movement of molecules= feels hot
↓ TEMP= ↓ movement of molecules= feels cold
Warm air= expanding or rising air= leaves behind L pressure
Cold Air=sinking air= leaves an area of H pressure
Uneven heating of the earth’s surface causes some areas to be warmer than others.
As we know, warm always follows cold to share it’s warmth- when this happens in the atmosphere, wind happens!
What causes winds?
A wind is a horizontal movement of air from a area of high pressure to an area of low pressure
It is this difference in pressure that makes the air move=wind
Winds are measured by direction and speed
The anemometer is the tool we use to measure this
Wind chill= ↑ cooling the wind causes
The land cools and heats faster than the ocean. Water holds heat longer than land, and takes longer to heat or cool.
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!
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 Wind Systems
Solar energy is at its greatest around the equator---Why?
Horse Latitudes = 30 °N and S of
equator =calm winds= worlds
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 area of low pressure. This is why most rain forests are found along equatorial regions.
That air rises until it reaches the top of the troposphere, where it can’t rise any further.
It spreads out towards the polar regions HOT follows COLD wanting to share its warmth.
As it spreads it begins to cool and sink-usually 30 °N and S of the equator- sinking air produces an area of H pressure with dry conditions= desert regions on earth
Some or the air moves back towards the equator as it sinks...
Where do you think
they got their name?
Who were these winds
particularly important to?
There was an area that sailors avoided with their lives...
THE DOLDRUMS... is the area around the equator where the wind completely dies out... which meant death as soon as the fresh water ran out.
Water in the Atmosphere: Humidity
Humidity : measure of the amount of water vapor stuck between molecules in the air. The air’s ability to hold water depends on the air temp
The hotter the air, the more water the air can hold
Cold air: molecules move slower so droplets of water can start to stick together= condensation
Relative humidity : the amount of water vapor(%) compared to the amount the air can hold- tool used is a psychrometer.
100%=air is saturated
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
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
descending (going down)=H pressure
ascending (going up)=L pressure
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 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
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
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