Transcript The Weather Recipe

The Weather Recipe
3 MAIN INGREDIENTS
What causes weather?
 Weather is not a set of random acts of
nature, it is a response to the unequal
heating of Earth’s atmosphere.
Ingredient #1: Atmospheric Pressure
 Weight of the column of
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air above a location.
Measured in millibars or
inches of mercury.
Influenced by heat.
Changes continually.
Low P indicates unstable
air, cloudiness and
storms.
Hi P indicated fair
weather and clear skies.
Ingredient #2: Moisture
 Vapor form of water has
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the most influence on
weather.
Varies with height,
latitude, longitude, and
time.
Tropics = 4%
Tropopause = 3 ppm
Expressed as relative
humidity.
Effects weather due to
energy content.
Ingredient #3: Heat
 Fuels the weather
machine.
 Determined by the speed
of molecules within a
substance.
 Transferred by radiation,
convection, and
conduction.
 Temperature is a
measure of the amount
of heat.
Earth’s Heat Budget
Effect of Earth’s Motions
 The atmosphere
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swaddles a rotating,
revolving planet.
Tilted axis (23.5 deg.)
causes seasonal changes.
Coreolis Force
Pressure gradient force
Friction
Air flows from regions
of higher pressure to
those of lower
pressure.
This difference is
called a pressure
gradient and drives
the wind direction
and speed.
Because of the
coreolis effect air does
not flow directly
toward low pressure
areas but is instead
deflected.
Pressure Gradient Force
Air Masses
A large body of air that has
properties similar to the
part of the Earth’s surface
over which it develops.
Clouds
 Masses of small water droplets or tiny ice crystals
that float in the air.
 Three main types are cirrus, cumulus, and stratus.
 Other clouds are a mixture of these three main types.
Cloud Types
Cirrus
High altitude clouds
Thin wisp like strands
Indicate an
approaching front and a
change in the weather
Cumulus
Puffy or cotton like in
appearance
Form as a warm air
mass rises into cooler
air
May produce heavy
rain, lightning, severe
and strong winds, hail,
and even tornadoes
Stratus
Strato- means “layerlike” or “sheet-like.”
Low-lying, dull-colored
clouds that form in
layers or sheets.
Usually bring drizzling
rain or light-falling
snow.
More detailed types of clouds
Types of Precipitation
Rain
Sleet
Snow
Hail
Air Masses
A large body of air that has
properties similar to the
part of the Earth’s surface
over which it develops.
Air Mass Map
Fronts
 A boundary between two air masses
of different density, moisture, or
temperature.
Cold Front
Cold fronts occur when
heavy cold air pushes
lighter warm air
upwards.
Cumulus clouds form
and usually grow into
thunderstorms
Temperatures drop
anywhere from 5
degrees to 15. Winds
become gusty and
erratic.
Rain, snow, sleet, and
hail can occur with a
cold front.
Cold Front
Warm Front
the leading edge of an
advancing mass of
warm air
The warm front symbol
on a weather map
marks the warm-cold
boundary at the earth's
surface. The circles on
the red line point in the
direction the warm air
is moving.
As the warm air rises
the water vapor
condenses into clouds
that can produce rain,
snow, sleet or freezing
rain, often all four.
Warm Front
Occluded front
Often, in the later
stages of a storm's life
cycle, a frontal
occlusion occurs.
Frontal occlusions
occur when storms
redevelop farther back
into the cold air. In
most cases, storms
begin to weaken after a
frontal occlusion occurs
Occluded Front
Stationary Front
Rainbows
Rainbows are optical
illusions and that cause
a spectrum of light to
appear in the sky when
the Sun shines onto
droplets of moisture in
the atmosphere.
They take the form of a
multicolored arc, with
red on the outer part of
the arch and violet on
the inner section of the
arch.
Contrails
The condensation trail
left behind jet aircrafts
Contrails form when
hot humid air from jet
exhaust mixes with
environmental air of
low pressure and low
temperature
Halos
Mostly caused by ice
crystals in cold cirrus
clouds located high (5–
10 km, or 3–6 miles) in
the upper troposphere
Light is reflected and
refracted by the ice
crystals and may split
up into colors because
of dispersion, similar to
the rainbow.
Global Air Circulation
 Heat and moisture are distributed over the earth’s
surface by vertical currents that form six large
convection currents at different latitudes.
 Called Hadley cells, the direction of airflow and the
ascent and descent of air masses in these cells
determines earth’s general climatic zones.
 The uneven distribution of heat and moisture over
the planet’s surface leads to the formation of
different biomes.
Global Air Circulation Patterns
Ocean Currents
 The oceans absorb heat from the air circulation
patterns.
 The majority of the heat is absorbed near the tropics.
 This heat plus differences in water density create
warm and cold ocean currents.
 These currents, driven by winds and the earth’s
rotation, redistribute heat received from the sun
from one place to another and thus influence climate
and vegetation.
Ocean Currents
Normal Conditions
El Niño
El Niño occurs when a
change in the direction
of tropical winds warms
coastal surface water,
suppresses upwellings,
and alters much of the
earth’s weather.
El Niño
La Niña
•As El Niño
conditions begin to
right themselves
(return to normal).
•The trade winds and
upwelling become
unusually strong
•ocean surface cools
far below normal
•causes widespread
climate disruptions
that often have the
opposite effect of
those caused by El
Niño
El Niño v. La Niña
La Niña
Key Points
 The surface of the earth is heated unevenly due to
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the angle the sun’s rays strike the earth
Rotation of the earth deflects air masses setting up
global air circulation patterns
Properties of air, water and land affect global air
circulation.
The oceans absorb heat from air circulation creating
warm and cold ocean currents.
Ocean currents redistribute heat from one place to
another and thus influence climate and vegetation
(biomes)
Thermohaline
large-scale ocean
circulation that is
driven by global density
gradients created by
surface heat and
freshwater fluxes.