The Study of Atmosphere and its Processes
WEATHER VS. CLIMATE
Weather is the day-to-day atmospheric conditions
in a specific time and place.
Climate is the average weather conditions in a
specific location over a long period of time. To be
classified as climate the weather conditions are
usually recorded over a 30 year period.
HISTORY OF THE ATMOSPHERE
Like everything else in the natural universe,
Earth’s atmosphere has been continually evolving
since its birth approximately 4.6 billion years ago.
It is theorized that Earth is now in its fourth major
atmosphere.
EARTH’S FIRST ATMOSPHERE
Earth’s first atmosphere was believed to be
composed mainly of hydrogen and helium.
However, due to Earth’s small size and low
gravitational pull, scientists suggest that the gases
were not able to be held in place and were simply
lost to space.
EARTH’S SECOND ATMOSPHERE
As Earth grew in size and mass so did its
gravitational pull. The second atmosphere is
believed to be composed mainly of CO2, Sulfur
Dioxide (SO2), H2O vapor, and Nitrogen (N2) that
came from the “outgassing” of volcanoes that
covered Earth’s newly formed crust.
EARTH’S THIRD ATMOSPHERE
In this atmosphere it is theorized that cyanobacteria
multiplied, converting a CO 2 rich atmosphere into a
oxygen rich atmosphere. In this new atmosphere, single
cell organisms would have begun to evolve into more
advanced multicellular organisms. The biodiversity of life
on our planet began.
FOURTH ATMOSPHERE
The fourth atmosphere is our atmosphere. Our
atmosphere is composed of two classes of gases:
Permanent Gases which remain relatively constant
and Variable gases which are mainly associated
with atmospheric cycles.
EARTH’S PERMANENT GASES
Some of earth’s atmospheric gases are considered to be
permanent because their percentages are stable and
constant. The three main gases include:
1. Nitrogen – 78%
2. Oxygen - 21%
3. Argon
- .93%
VARIABLE GASES
Some of Earth’s gases are considered to be variable
because they are constantly changing in cycles. The
main variable gases include:
1. Water Vapor
- .25% (Hydrologic Cycle)
2. Carbon Dioxide - .036% (Carbon Cycle)
3. Ozone
4. Methane
- .01%
- .01% (normal level, currently1.7%)
AEROSOLS
Aerosols are Small solid particles and liquid droplets in the
air. (Not including: water vapor and precipitation)
Forms from natural and human processes
In a normal human breath, our lungs takes in approx. 1000
cm3 ,(1 Liter), of air. As a result, approx. 1 million aerosols
are taken into our lungs several times a minute, or about
2 tablespoons of solids each day.
Condensation Nuclei: Necessary for Cloud formation, and
precipitation to form.
LAYERS OF THE ATMOSPHERE
There are 4 main layers of Earth’s atmosphere.
1. Thermosphere
2. Mesosphere
3. Stratosphere
4. Troposphere
THERMOSPHERE
The thermosphere is the fourth and highest layer of our
atmosphere. The thermosphere begins at approximately 90
km above the surface and ends at 2400 km. The
thermosphere is divided into 4 sub-layers.
1. Lowest layer: Nitrogen
2. Ionosphere:
Layer of charged particles. (Auroras)
3. Middle layer: Helium
4. Highest Layer: Hydrogen
MESOSPHERE
The third layer is the mesosphere. This layer is at
an altitude of 50 to 90 km above the surface.
STRATOSPHERE
The second layer is the stratosphere. This layer is
at an altitude of 16 to 50 km above the surface.
Located within this layer is the ozone layer. The
ozone layer protects earth’s surface from
excessive ultraviolet solar radiation by converting
UV radiation into heat.
OZONE CYCLE
TROPOSPHERE
The first layer of the atmosphere is the
Troposphere which is 0 – 16 km thick at the
equator and only 0 – 9km at the poles)
The troposphere accounts of 80% of the total
atmosphere.
All life on Earth in contained within the
troposphere.
EARTH’S ENERGY BALANCE
In order for Earth to maintain its stable temperature,
100% of the incoming solar radiation must be balanced
with an equal amount of outgoing energy. A mere 10 0 F
change in temperature up or down could melt the ice
caps and raise ocean levels 200 ft or send Earth into an
ice age with glaciers covering 70% of the surface.
ENERGY BUDGET
ATMOSPHERIC PROTECTION FROM SOLAR
RADIATION
EARTH’S MAJOR AIR MASSES
Air masses are large bodies of air in the lower
troposphere which have similar characteristics
throughout.
Types of air masses:
cA – Continental Arctic – Very Cold and Dry
cP – Continental Polar – Cold and Dry
cT – Continental Tropical – Hot and Dry
mP – Maritime Polar – Cool and Moist
mT – Maritime Tropical – Warm and Moist
AIR MASSES
GLOBAL WIND PATTERNS
Three Cell Model
Polar Cells
Ferrell Cells – Mid-Latitudes
Hadley Cell – Intertropical Convergence
Zone (ITCZ)
GLOBAL WIND PATTERNS
GLOBAL WIND PATTERNS
AIR PRESSURE SYSTEMS
HIGH PRESSURE SYSTEMS
• Coriolis Effect deflects air to the right in the northern
hemisphere
• Winds rotate clockwise in the northern hemisphere
(Anticyclone)
• High pressure systems blow cool, dry air from the
upper atmosphere down toward the surface
H
LOW PRESSURE SYSTEMS
Low pressure systems rotate Counterclockwise in
the northern hemisphere. (Cyclone)
• Low pressure system draw warm moist air from the
surface and blow up into the upper atmosphere
where it cools and condenses from a gas to a
liquid.
L
LOW PRESSURE SYSTEM
HIGH & LOW PRESSURE INTERACTION
FRONTS
A Front is the boundary that separates two opposing
air masses.
Symbol Key:
COLD FRONT
A Cold Front is the boundary between an advancing cold
air mass and the warmer air mass it is displacing.
Characteristics of a cold front:
• Fast moving: Average speed 10 - 30 mph
• Normally in a steep wedge shape
• Cloud cover will usually be cumuliform
• Associated with heavy precipitations
• Dramatic decrease in temperature: 10 degrees or more
• High winds
COLD FRONT
WARM FRONT
A Warm Front is the leading edge of advancing warm air
that rises above the denser cold air mass in a process
known as overrunning.
• The wedge shape is much more gradual than a cold
front.
• Signs of an approaching warm front:
1. Fair weather
2. Cloud Formation
3. Associated with light steady rain
WARM FRONT
STATIONARY FRONT
A stationary front is a non-moving boundary between a
cold front and a warm front.
• If there is no movement of air masses in a three hour
period, then the front is considered stationary.
STATIONARY FRONT
OCCLUDED FRONT
Since cold fronts move twice as fast as a warm front,
the warm front is typically overtaken by the cold
front. When this occurs, warm air gets trapped and
forced upward which cools and often causes
cloudiness and precipitation.
OCCLUDED FRONT
LIFE CYCLE OF A MID-LATITUDE
CYCLONE
• Cyclogenesis: the birth of a mid-latitude cyclone
• Occurs only in the temperate zones
• Largest weather system on the planet, ranging
from 100 – 1500 miles in diameter
PHASE 1
A polar front separates the cold easterlies and the
warmer westerlies.
PHASE 2
• A minor kink develops along the boundary. The
cold air north of the front begins to push southward
behind the cold front, and air behind the warm front
advances northward.
• This creates a counterclockwise rotation around a
weak developed low pressure system. Continued
uplift leads to cloud formation.
PHASE 2
PHASE 3
• A band of cumuliform cloud cover runs along and
ahead of the cold front, caused by the displacement
of the warm air by the cold denser air.
• Because of the high moisture content, intense rain,
snow, and hail could occur.
PHASE 3
PHASE 4
The system becomes occluded and loses it warm,
moist air fuel. The system begins to shut down.
CLOUD FORMATION
Adiabatic Process:
• Parcel: A pocket of air which is heated by the earth’s
surface by the process of conduction.
• Relative Humidity: The amount of water vapor in the air
at a given temperature compared to the total amount of
water vapor that the air could hold (saturation: 100%)
• Inverse relationship: As the temperature decreases, the
relative humidity increases.
ADIABATIC PROCESS CONT.
• Normal Lapse Rate: Ambient air temperature will
decrease at an average of 6.50 C per every 1000 m.
• Dry Adiabatic Lapse Rate: As the parcel of air rises
the warmer air inside will decrease at a rate of 100 C
per 1000 m.
• Wet Adiabatic Lapse Rate: When the parcel of air
reaches 100% relative humidity, the lapse rate will
decrease to 50 C per 1000 m
ADIABATIC PROCESS CONT.
CLOUD TYPES
There are four basic categories of clouds:
• Cirrus –
Thin, wispy clouds made of ice crystals
• Stratus – Layered clouds
• Cumulus – Vertical developed
• Nimbus – Rain producing clouds
CLASSIFICATION OF CLOUDS
• High clouds: cirrus, cirrostratus, and cirrocumulus
• Middle clouds: altostratus and altocumulus
• Low clouds: stratus, stratocumulus and
nimbostratus
• Clouds with extreme vertical development:
cumulus and cumulonimbus
HIGH CLOUDS
Cirrus
Cirrostratus
Cirrocumulus
MIDDLE CLOUDS
Altostratus
Altocumulus
LOW CLOUDS
Stratus
Stratocumulus
Nimbostratus
EXTREME VERTICAL DEVELOPMENT
Cumulus
Cumulonimbus
THUNDERSTORMS
The are three stages in the formation of a
thunderstorm:
Stage 1: Cumulus Stage
Stage 2: Mature Stage
Stage 3: Dissipation Stage
CUMULUS STAGE
In the cumulus stage, an unstable parcel of air
begins to rise due to by localized convection.
• The parcel of air cools adiabatically and creates the
cumulus cloud.
• The atmosphere becomes humid enough that the newly
formed cloud does not evaporate, but grows vertically.
CUMULUS STAGE
MATURE STAGE
• In the mature stage, heavy precipitation
begins to fall in the form of rain.
• Updrafts form in the interior of the cloud
• Down drafts form the most severe
precipitation
MATURE STAGE
MATURE STAGE
DISSIPATION STAGE
In the dissipation stage down drafts cut off the warm, moist
air supply, that begins to shut down the entire system.
LIGHTNING
Charge Separation:
• In order for lightning to be created there must first be
a separation between positively and negatively
charged atoms. Most often the positively charged
particles accumulate in the upper portions of the
cloud and the negatively charged particles in the
lower portions with another layer of positively
charged particles at the base of the cloud.
CHARGE SEPARATION
TYPES OF LIGHTNING
For lightning to occur, static electricity builds up
within the cloud essentially becoming a massive
battery.
There are four main types of lightning:
1. Internal cloud lightning
2. Cloud to air lightning
3. Cloud to cloud lightning
4. Cloud to ground lightning
INTERNAL CLOUD LIGHTNING
Internal lightning occurs when a static charge is discharged
within a cloud. This type of lightning is sometimes called
“Heat Lightning”. However, heat lightning does not exist.
CLOUD TO AIR LIGHTNING
CLOUD TO CLOUD LIGHTNING
In cloud to cloud lightning, one cloud in the system
discharges into a nearby cloud.
• 80% of lightning is between clouds
• Cloud –to- cloud occurs when the voltage gradient
within or between clouds overcomes the electrical
resistance of the air.
CLOUD TO CLOUD
CLOUD TO GROUND
• Cloud to ground occurs the negatively charged
particles accumulate in the base of the cloud and the
positively charged particles that were at the base are
forced to the ground.
• The negatively charged particles in the base of the
cloud are repelled toward the ground forming a
negatively charged column of ionized air called a
“Stepped Leader”.
CLOUD TO GROUND CONT.
• When the stepped leader reaches the ground and
connects with the positively charged particles, the
circuit is completed allowing the flow of electrons
to occur. This known as the “return stroke”.
• The lightning bolt originates at the ground and
travels back to the cloud .
CLOUD TO GROUND CONT.
• The electrical charge of the average lightning bolt is
approximately 20,000 amperes and reaches
temperatures in excess of 30,0000 K or 54,0000 F or
five times hotter than the surface of the sun.
• The amount of amperes required to stop a human
heart is approximately .056 amps.
CLOUD TO GROUND CONT.
• In a tenth of second following the main discharge,
up to five smaller, sequential, discharges may
occur that are called “dart leaders”. These
discharges together happen so fast that the
lightning appears to flash
CLOUD TO GROUND CONT.
SPECIAL LIGHTNING
THUNDER
• Thunder occurs when superheated air from a lightning
strike cools and produces a resonating tube
surrounding the lightning's path. The nearby air rapidly
expands and contracts. This causes the column to
vibrate like a tubular drum head and produces a
tremendous crack.
• The more forks off of the main bolt, the longer the
rumble will be after the main crack.
SUPERCELL THUNDERSTORM
• A very large, single-cell thunderstorm with
particularly strong up drafts. The updrafts of a
super-cell rotates which could result in tornado
development.
• Super-cell thunderstorms are responsible for the
highest wind speed, most damaging hail, and the
most destructive tornadoes.
SUPERCELL THUNDERSTORM
BIRTH OF A TORNADO
TORNADOES
• Tornadoes are the most violent of all the storms on Earth.
Wind speeds can reach in excess of 300 mph.
• Tornadoes rotate cyclonically, (counter-clockwise) in the
northern hemisphere 98% of the time.
• Tornadoes are zones of extremely rapid, rotating winds
below a cumulonimbus cloud.
TORNADOES CONT.
• Strong tornadic winds form as a result of extremely
large differences in atmospheric pressure over a
short distance. Normally, the difference between a
high and low pressure system is about 35 mb over
thousands of kilometers. However, over just tenths
of a kilometer the pressure difference from the core
of the tornado and the outside air can be as great
as 100 mb.
STAGE 1
• Fast moving air from the upper atmosphere opposes
fast moving air in the lower atmosphere resulting in a
rolling column of air between deep within the cloud
called a mesocyclone.
• In order for a tornado to form, the mesocyclone must
be at least approximately 6 miles in diameter.
FORMATION OF A MESOCYCLONE
STAGE 2
• Strong updrafts tilt the mesocyclone vertical. This
produces the rotation of the clouds interior.
• The mesocyclone narrows and wind speeds
increase. As the mesocyclone narrows and winds
increase the base of the column rotating air
becomes more dense and begins to descend from
the base of the cloud creating a “wall cloud”.
STAGE 2
WALL CLOUD
STAGE 3
When the narrow, rapidly rotating vortex emerges
through the wall cloud a “funnel cloud” is formed.
STAGE 4
When the funnel cloud reaches the surface, it becomes
a tornado.
ENHANCED FUJITA SCALE
TORNADO WATCHES AND WARNINGS:
•
Watch: A tornado watch is issued when weather
conditions are favorable for tornadoes to form.
These include heavy precipitation, high winds and
large hail.
• Warning: A tornado warning is issued when a
tornado has been observed on the ground and
moving in a specific direction.
SATELLITE IMAGE OVER JOPLIN MISSOURI
MAY 25TH 2011
DOPPLER RADAR IMAGES OF JOPLIN MISSOURI,
MAY 22, 2011
EF5 TORNADO
DESTRUCTION
HURRICANES
• Hurricanes are the most powerful of all storms .
• The energy released by a single hurricane is more
than the power consumption of the United States.
• Hurricane season in the northern hemisphere is
from June 1st to November 30th.
NAMES OF HURRICANES
• Over the Atlantic and Eastern Pacific oceans –
Hurricanes
• Over the Western Pacific Ocean – Typhoons
• Over the Indian Ocean and Australia – Cyclones
STAGES OF HURRICANE
DEVELOPMENT
There are four stages in the development of a
hurricane.
Stage 1: Tropical Disturbance
Stage 2: Tropical Depression
Stage 3: Tropical Storm
Stage 4: Hurricane
STAGE 1
• Tropical Disturbance: A disorganized cluster of
thunderstorms form in the southern Atlantic Ocean
above 50 latitude. 90% of tropical disturbances do not
develop further.
STAGE 2
• Tropical Depression: The pressure lowers causing
the tropical disturbance to begin organizing in to
bands of thunderstorms with cyclonic rotation. The
system closes around a central point.
STAGE 3
• Tropical Storm: When wind speeds increase to 37
mph, the eye is named.
STAGE 4
• When the wind speed reaches 74 mph, and water
temperature is above 790 F, the storm is classified as
a Category 1 hurricane.
THE EYE
• Eye: A region of extreme low pressure, clear skies,
descending air and light winds.
• The eye of a hurricane can range from 3.5 miles to 60
miles across.
EYE WALL
• Eye Wall: The eye wall is the outer edge of the eye.
• This is the area of the most intense storm activity,
strongest winds, thickest cloud cover, and most intense
precipitation (100 in per day).
SPIRAL ARMS OF A HURRICANE
• Spiral bands of a hurricane are composed of numerous
thunderstorms spinning counterclockwise around the
eye.
UPDRAFTS & DOWNDRAFTS
SAFFIR-SIMPSON SCALE
STATION MODELS
• Using the huge amount of data collected by
weather reporting stations, Meteorologists use
symbols to create weather maps called station
models.
SAMPLE MODELS