Transcript Meteorology - BierScience: SHHS Earth and Physical Science

Credits
www.epa.gov/airnow/2004conference/.../ne
se_meteorology_101.ppt
Meteorology 101. Fundamentals of Weather.
Jon Nese and Jen Carfagno. The Weather
Channel. February 22, 2004.
Meteorology 101
Questions to Answer
• How, why, when, where does the
wind blow?
• What controls vertical motions?
• When and where do clouds and
precipitation form?
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What are two differences between a
warm and cold front?
What are two differences between a Low
Pressure System and a High Pressure
System?
Meteorology 101
Geographical Terminology…
Meteorology 101
Layering of the Atmosphere
Stratosphere
6-8
Altitude
(mi)
Troposphere
Temperature
Planetary
Boundary
Layer
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78.09% nitrogen
20.95% oxygen
0.93% argon
0.039% carbon dioxide
Small traces of other gases
Variable amounts up to 1% of water vapor
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Troposphere—lowest layer
(upper boundary called
tropopause)

Temperature decreases with
altitude
 Rate of cooling is variable but
averages about 6.5ºC per km
 Stops decreasing at
tropopause—9km at poles and
16km at the equator
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Contains the most water
vapor
Contains about 80% of the
mass of the atmosphere
Jet stream is located just
under tropopause
All Earth’s weather occurs
here.
High-Level Clouds (Cirrus)
High-level clouds form above 20,000
feet (6,000 meters) and since the
temperatures are so cold at such
high elevations, these clouds are
primarily composed of ice crystals.
High-level clouds are typically thin
and white in appearance, but can
appear in a magnificent array of
colors when the sun is low on the
horizon
Mid-Level Clouds
The bases of mid-level clouds
typically appear between 6,500 to
20,000 feet (2,000 to 6,000 meters).
Because of their lower altitudes, they
are composed primarily of water
droplets, however, they can also be
composed of ice crystals when
temperatures are cold enough.
Low-level Clouds
Low clouds are of mostly composed of water droplets since their
bases generally lie below 6,500 feet (2,000 meters). However,
when temperatures are cold enough, these clouds may also
contain ice particles and snow.
Vertically Developed Clouds
Probably the most familiar of the classified clouds is the cumulus
cloud. Generated most commonly through either thermal
convection or frontal lifting, these clouds can grow to heights in
excess of 39,000 feet (12,000 meters), releasing incredible
amounts of energy through the condensation of water vapor
within the cloud itself.
Vertically Developed Clouds
Fair Weather Cumulus
Vertically Developed Clouds
Cumulonimbus clouds (Cb) are much larger and more vertically
developed than fair weather cumulus. They can exist
as individual towers or form a line of towers called a squall line.
Fueled by vigorous convective updrafts (sometimes in excess 50
knots), the tops of cumulonimbus clouds can easily reach 39,000
feet (12,000 meters) or higher.
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Orographic Clouds
forced by the
earth's topography
Orographic clouds
are clouds that
develop in response
to the forced lifting
of air by the earth's
topography
(mountains for
example).
•Exosphere
Outer •Thermosphere
Mid
•Mesosphere
•Stratosphere
Low
•Troposphere
•Earth

Stratosphere—second layer (upper boundary
called stratopause)
Clear, dry layer
 50km above the Earth’s surface
 Lower part is about as cold as tropopause
 Warms steadily to stratopause

 Warming due to ozone
 Ozone absorbs uv rays and releases some as heat

How do we reduce damage to the ozone layer?
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Mesosphere—third layer (upper boundary called
mesopause)
50km to 90km above the Earth’s surface
 Temperature drops with altitude
 Layer where meteors burn up
 Noctilucent clouds form here
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Thermosphere—outermost layer

Temperature rises with altitude
 Temperatures can rise above 1000ºC
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Extremely thin; few molecules
 Highest layers—composed of lighter gases (He, H2)
 Lowest layers—composed of heavier gases(N2,O2)
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Contains the ionosphere
 Located between 90 and 500km
 Air is highly ionized due to the uv rays
 Affected by solar events
 Can disrupt radio transmissions
 Form auroras
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Thermosphere (con’t)
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Contains the ionosphere
 Located between 90 and 500km
 Air is highly ionized due to the uv rays
 Affected by solar events
 Can disrupt radio transmissions
 Form auroras
Meteorology 101
Some Fundamentals
• Earth is heated unevenly: Tropics are
warmer than the Polar Regions.
• Nature tries to try to even out
temperature differences.
• Uneven heating sets atmosphere in
motion and is the fundamental cause
of all weather.
Meteorology 101
Radiation is the transfer of thermal
energy by electromagnetic waves
Meteorology 101
Convection is the transfer of energy by the
movement of heated material from one place
to another.
Conduction is the transfer of energy between
objects when their molecules collide
Meteorology 101: What is this?
Warm Air Mass?
Cold Air Mass?
Moist Air Mass?
Meteorology 101: What is this?
A Cold Front
Meeting a
Warm Air Mass.
When cold air
contacts warm
air???
Warm air rises into
cooler atmosphere
Condensation
occurs (Rain)
Meteorology 101: What is this?
Cumulonimbus
Supercell
Thunderstorm
Meteorology 101: What is this?
Lake Effect
Snow
Warm water evaporates.
The warm water moves over land
The land is cooler.
Precipitation occurs (condensation)
Meteorology 101
Isobars (like a
topographic map of
atmospheric
pressure)
Millibars (like
pounds of
pressure)
How would you describe the change in atmospheric
pressure along the orange arrow?
Meteorology 101
How many times more dense is the
troposphere than the thermosphere?
Meteorology 101
The Coriolis Effect
Meteorology 101
The Coreolis Effect
Meteorology 101
Meteorology 101
Air Pressure
“Top”
On average, air weighs
about 14.7 lb/in2
14.7 lb/in2 =29.92
“inches of mercury”
1”
1”
Air Pressure varies over
the globe
Meteorology 101
Changing Pressure - Winds
Take more out than put in – decrease pressure
Put more in than take out – increase pressure
Meteorology 101
Changing Pressure - Temperature
Cold
Warm
Coldest column = highest pressure **
Warmest column = lowest pressure **
Meteorology 101
Pressure Differences Create Wind
Air moves from higher toward lower pressure
Meteorology 101
Vertical motions also occur
Air “converges” at lows, and rises.
Air “diverges” at highs, and sinks.
Meteorology 101
Reality is more complicated
Actual winds around highs and lows
Meteorology 101
Rising Air near
ows
• Rising air cools; water vapor in the air
condenses to form clouds/precipitation
• Lows tend to bring cloudy, wet weather
Sinking air near
ighs
• Sinking air warms and dries out.
• Highs tend to bring fair, dry weather.
Meteorology 101
Low or lowering pressure = “Lousy” weather
Meteorology 101
Cold
Warm
General Circulation
Meteorology 101
Cold
Warm
Front =
Battleground of
Air Masses
• Temperature
differences
concentrated
• Zone of lower
pressure where
lows (storms)
often form
Meteorology 101
Cold Front
Colder
Warmer
Colder
Warmer
Cold air advances
Warm Front
Warm air
advances*
Colder
Warmer
Stationary Front
Meteorology 101
What happens when air masses meet at
fronts?
Cold
Warm
Cold air lifts the warmer air.
Clouds and precipitation form.
Meteorology 101
Ridge
UpperLevel
Features
Trough
Westerlies - High-Altitude winds blow
generally west-to-east 3-6 miles above midlatitudes.
Jet Stream – River of fastest-moving air
within the westerlies.
Meteorology 101
Reality is messier …
Still, highs and Lows move with the
westerlies and the jet stream.
Meteorology 101
RIDGE
SINKING
AIR
HIGH
PRESSURE
FAVORED
TROUGH
RISING
AIR
LOW
PRESSURE
FAVORED
Highs and Lows form and dissipate in synch with
ridges and troughs in the westerlies.
Meteorology 101
LOW
This
is
your
life!
COLD
WARM
Stationary Front separates air masses
Meteorology 101
LOW
This
is
your
life!
COLD
WARM
Area of low pressure develops along front
Meteorology 101
LOW
This
is
your
life!
Circulation around low sends cold air and
warm air advancing
Meteorology 101
COLD
LOW
This
is
your
life!
COLD
WARM
Low and fronts move with the upper-air
westerlies while circulating low-level air
Meteorology 101
LOW
This
is
your
life!
Cloud
Shield
Precipitation
Shield
Warm
Sector
Typical cloud and precipitation shield of a
low-pressure system and fronts
Meteorology 101
Intense lows
often take on a
“comma-cloud”
shape when
viewed from
space.
Meteorology 101
Local Winds
Warm
Sea Breeze
Land
Heats
faster
Water
Uneven heating working on a smaller scale