Download Weather - Elgin ISD

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 Movement
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

Local Winds

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
SEA BREEZE
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 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 Wind
Systems
Solar
energy is at its
greatest around the
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
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 of the air moves back
towards the equator as it sinks...
Tradewinds:
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
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
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

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

This is the symbol
for a cold front
Cold air pushes under a warm air mass.
Warm air rises quickly=narrow bands of
violent storms form
Occluded Front

This is the
weather map
symbol for an
occluded front
2 air masses merge and force warm air
between them to rise quickly. Strong
winds and heavy precipitation will occur
Stationary Front

This is the
weather map
symbol for a
stationary front
Warm or cold front stops moving. Light
wind and precipitation may occur across
the front boundary
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