CLIMATE:
WIND
THUNDERSTORMS
CYCLONES
What is CLIMATE?
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Climate is a measure of the average pattern of
variation in temperature, humidity, atmospheric
pressure, wind, precipitation, atmospheric particle
count and other meteorological variables in a given
region over long periods of time. Climate is different
from weather, in that weather only describes the
short-term conditions of these variables in a given
region.
A region's climate is generated by the climate
system, which has five components: atmosphere,
hydrosphere, cry sphere, land surface, and
biosphere.[1]
Climate (from Ancient Greek klima,
meaning inclination) is commonly
defined as the weather averaged
over a long period.[3] The standard
averaging period is 30 years,[4] but
other periods may be used
depending on the purpose. Climate
also includes statistics other than
the average, such as the
magnitudes of day-to-day or yearto-year variations.
FACTORS OF CLIMATE:
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The climate of a location is affected by its latitude,
terrain, and altitude, as well as nearby water
bodies and their currents.
Climates can be classified according to the average
and the typical ranges of different variables, most
commonly temperature and precipitation.
The most commonly used classification scheme was
originally developed by Wladimir Köppen. The
Thornthwaite system,[2] in use since 1948,
incorporates evapotranspiration along with
temperature and precipitation information and is used
in studying animal species diversity and potential
effects of climate changes. The Bergeron and Spatial
Synoptic Classification systems focus on the origin of
air masses that define the climate of a region.
Difference between climate
and weather
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The difference between climate and weather is
usefully summarized by the popular phrase
"Climate is what you expect, weather is what you
get.”
The day to day conditions of the atmosphere at a
place with respect to the temperature, humidity,
rainfall, wind-speed, etc., is called the weather at
that place.
The weather is generally not the same on any two
days and week after week.
The average weather pattern taken over a long
time, say 25 years, is called the climate of the
place.
Climate classification
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There are several ways to classify climates into similar regimes.
Originally, climes were defined in Ancient Greece to describe
the weather depending upon a location's latitude. Modern
climate classification methods can be broadly divided
into genetic methods, which focus on the causes of climate,
and empiric methods, which focus on the effects of climate.
Examples of genetic classification include methods based on
the relative frequency of different air mass types or locations
within
synoptic
weather
disturbances.
Examples
of empiric classifications include climate zones defined by
plant hardiness,[10] evapotranspiration,[11] or more generally
the Köppen climate classification which was originally
designed to identify the climates associated with
certain
biomes.
A
common
shortcoming
of
these classification schemes is that they produce distinct
boundaries between the zones they define, rather than the
gradual transition of climate properties more common in
nature.
Climate change
 Climate
change is the variation
in global or regional climates
over time. It reflects changes in
the variability or average state
of the atmosphere over time
scales ranging from decades
to millions of years. These
changes can be caused by
processes internal to the Earth,
external forces (e.g. variations
in sunlight intensity) or, more
recently, human activities.[42]
Variations in CO2,
temperature and dust
from the Rostock ice core
over the past
450,000 years
WIND
Moving air is called WIND. In meteorology the term is usually
applied to the natural horizontal motion of the atmosphere; motion
in a vertical, or nearly vertical, direction is called a current. Winds
are produced by differences in atmospheric pressure, which are
primarily attributable to differences in temperature. Variations in the
distribution of pressure and temperature are caused largely by
unequal distribution of heat from the Sun, together with differences
in the thermal properties of land and ocean surfaces. When the
temperatures of adjacent regions become unequal, the warmer air
tends to rise and flow over the colder, heavier air. Winds initiated in
this way are usually greatly modified by the Earth's rotation.
Winds may be classified into four major types: the prevailing winds,
the seasonal winds, the local winds, and the cyclonic and
anticyclone winds, including cyclones, hurricanes, and tornadoes.
Anemometer (Greek, anemos, “wind”; metron,”measure”), an
instrument that measures wind speed. The most common kind of
anemometer consists of three or four cups attached to short rods
that are connected at right angles to a vertical shaft. As the wind
blows, it pushes the cups, which turn the shaft. The number of turns
per minute is translated into wind speed by a system of gears
similar to those in the speedometer of a motor vehicle. Wind velocity
is also measured by the pressure of the air blowing into a Pitot tube
(an L-shaped tube, one end open towards the flow of air and the
other end connected to a pressure-measuring device), or
electrically by the cooling effect of the wind on a heated wire, which
causes the electrical resistance of the wire to change.
THUNDERSTORMS and
LIGHTINING
A flash of lightning rips
through the night sky.
Lightning is the visible
electric discharge that
occurs between rain
clouds or between a rain
cloud and the earth.
All thunderstorms are dangerous. Every thunderstorm produces
lightning. While lightning fatalities have decreased over the past 30
years, lightning continues to be one of the top three storm-related
killers in the United States. In 2010 there were 29 fatalities and 182
injuries from lightning. Although most lightning victims survive,
people struck by lightning often report a variety of long-term,
debilitating symptoms.
Other associated dangers of thunderstorms include tornadoes,
strong winds, hail and flash flooding. Flash flooding is responsible for
more fatalities – more than 140 annually – than any other
thunderstorm-associated hazard. Dry thunderstorms that do not
produce rain that reaches the ground are most prevalent in the
western United States. Falling raindrops evaporate, but lightning can
still reach the ground and can start wildfires.
Before Thunderstorm and
Lightning
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To begin preparing, you should build an emergency
kit and make a family communications plan.
Remove dead or rotting trees and branches that could fall
and cause injury or damage during a severe
thunderstorm.
Postpone outdoor activities.
Remember the 30/30 Lightning Safety Rule: Go indoors if,
after seeing lightning, you cannot count to 30 before
hearing thunder. Stay indoors for 30 minutes after hearing
the last clap of thunder.
Secure outdoor objects that could blow away or cause
damage.
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Get inside a home, building, or hard top
automobile (not a convertible). Although you
may be injured if lightning strikes your car, you
are much safer inside a vehicle than outside.
Remember, rubber-soled shoes and rubber tires
provide NO protection from lightning. However,
the steel frame of a hard-topped vehicle
provides increased protection if you are not
touching metal.
Shutter windows and secure outside doors. If
shutters are not available, close window blinds,
shades or curtains.
Unplug any electronic equipment well before the
storm arrives.
IF YOU ARE:
THEN:
In a forest
Seek shelter in a low area under a thick
growth of small trees.
In an open
area
Go to a low place such as a ravine or valley.
Be alert for flash floods.
On open water
Get to land and find shelter immediately.
Anywhere you
feel your hair
stand on end
(which indicates
that lightning is
about to strike)
Squat low to the ground on the balls of your
feet. Place your hands over your ears and
your head between your knees. Make
yourself the smallest target possible and
minimize your contact with the ground. DO
NOT lie flat on the ground.
Why are there more thunderstorms
during the summer?
According to the National Oceanic and Atmospheric
Administration (NOAA) National Weather Service,
approximately 1,800 thunderstorms are occurring at
any given time, resulting in about 16-million
thunderstorms each year. Most thunderstorms last
about 30 minutes and are typically about 15 miles (24
km) in diameter.
Thunderstorms thrive under certain conditions. The
two most basic elements that cause a thunderstorm to
develop are:
 Moisture
 Rapidly rising warm air
Because moisture and warmth are crucial to
thunderstorms, it makes sense that they would occur
more often in the spring and summer, particularly in
humid areas. The high humidity, in conjunction with
warm temperatures, creates massive amounts of
warm, moist air rising into the atmosphere, where it
can easily form a thunderstorm.
Where does the thunder (and
lightning) come from?
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The basic idea is that thunder clouds can become giant
Van de Graff generators and create huge charge
separations within the cloud. Let's look at how it works.
Clouds contain millions and millions of water
droplets and ice particles suspended in the air. As the
process of evaporation and condensation occurs, these
droplets collide with other moisture that is condensing as it
rises. The importance of these collisions is that electrons
are knocked off of the rising moisture, creating a charge
separation. The newly knocked-off electrons gather at the
lower portion of the cloud, giving it a negative charge.
The rising moisture that has lost an electron carries a
positive charge to the top of the cloud.
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As the rising moisture encounters colder temperatures in the upper
cloud regions and begins to freeze, the frozen portion becomes
negatively charged and the unfrozen droplets become positively
charged. At this point, rising air currents have the ability to remove
the positively charged droplets from the ice and carry them to the
top of the cloud. The remaining frozen portion either falls to the
lower portion of the cloud or continues on to the ground.
The charge separation has an electric field associated with it. Like
the cloud, this field is negative in the lower region and positive in
the upper region. The strength or intensity of the electric field is
directly related to the amount of charge build-up in the cloud. As
the collisions and freezing continue to occur, and the charges at
the top and bottom of the cloud increase, the electric field
becomes more and more intense -- so intense, in fact, that the
electrons at the Earth's surface are repelled deeper into the Earth
by the negative charge at the lower portion of the cloud.
This repulsion of electrons causes the Earth's surface to acquire a
strong positive charge.
All that is needed now is a conductive path so the
negative cloud bottom can conduct its electricity
to the positive Earth surface. The strong electric field
creates this path through the air, resulting in
lightning. The lightning is a high-voltage, highcurrent surge of electrons, and the temperature at
the core of a lightning bolt is incredibly hot. For
example, when lightning strikes a sand dune, it can
instantly melt the sand into glass. The combination
of the rapid heating of the air by the lightning and
the subsequent rapid cooling creates sound waves.
These sound waves are what we call thunder. There
can never be thunder without lightning.
CYCLONES
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In meteorology,
a cyclone is an area
of closed, circular
fluid motion rotating
in the same
direction as
the Earth. This is
usually
characterized by
inward spiraling win
ds that rotate anticlockwise in
the Northern
Hemisphere and clo
ckwise in the
Southern
Hemisphere of the
Earth.
Most large-scale
cyclonic circulations
are centered on
areas of low
atmospheric
pressure.[3][4] The
largest low-pressure
systems are coldcore polar cyclones
and extra-tropical
cyclones which lie on
the synoptic scale
According to the NHC glossary, warm-core cyclones such as
tropical and subtropical cyclones also lie within the synoptic
scale. Mesocyclones, tornadoes and dust devils lie within the
smaller mesoscale. Upper level cyclones can exist without the
presence of a surface low, and can pinch off from the base of
the Tropical Upper Tropospheric Trough during the summer months
in the Northern Hemisphere.
Cyclones have also been seen on extraterrestrial planets, such
as Mars and Neptune.
Cyclogenesis describes the process of cyclone formation and
intensification.
Tropical cyclones form due to latent heat driven by significant
thunderstorm activity, and are warm core. Cyclones can transition
between extra-tropical, subtropical, and tropical phases under the
right conditions.
In the Atlantic basin, a tropical cyclone is generally referred to as
a HURRICANE (from the name of the ancient Central American
deity of wind, Huracan),
CYCLONE in the Indian Ocean and parts of the Pacific
TYPHOON in the Northwest Pacific region
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Fronts are associated with
cyclones, or areas of low
pressure, and occur when cold
air masses meet warm ones . The
circulation of the Earth’s
atmosphere causes the cold air
to move eastwards and equator
wards and the warm air to move
eastwards and pole wards in a
wedge shape called the warm
sector . This movement causes
the front to buckle , with a warm
front to the east, where the
leading edge of the warm sector
is replacing cold air, and a cold
front to the west . Because cold
air moves faster than warm air,
the warm sector is gradually
squeezed and the front occludes
and decays.
SYNOPTIC SCALE
A fictitious synoptic chart of an extra-tropical cyclone
affecting the UK and Ireland. The blue arrows
between isobars indicate the direction of the wind, while
the "L" symbol denotes the center of the "low". Note the
occluded, cold and warm frontal boundaries.
Surfacebased types There are three main types
surface-based cyclones:
Extra-tropical
cyclones
Subtropical cyclones
Tropical cyclones
Extra-tropical cyclone
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An extra-tropical cyclone is a synoptic scale lowpressure weather system that does not
have tropical characteristics, being connected with fronts and
horizontal gradients in temperature and dew point otherwise
known as "baroclinic zones".
The descriptor "extra-tropical" refers to the fact that this
type of cyclone generally occurs outside of the tropics, in the
middle latitudes of the planet. These systems may also be
described as "mid-latitude cyclones" due to their area of
formation, or "post-tropical cyclones" where extra-tropical
transition has occurred, and are often described as
"depressions" or "lows" by weather forecasters and the
general public. These are the everyday phenomena which along
with anti-cyclones, drive the weather over much of the Earth.
Subtropical CyclonesSubtropical Storm
Andrea in 2007
A subtropical cyclone is
a weather system that has
some characteristics of
a tropical cyclone and some
characteristics of
an extratropical cyclone.
They can form between the
equator and the 50th
parallel.
Tropical Cyclones -
2013 Atlantic hurricane season summary map
A tropical cyclone is a storm system characterized by a lowpressure center and numerous thunderstorms that produce strong winds
and flooding rain. A tropical cyclone feeds on heat released when
moist air rises, resulting incondensation of water vapour contained in the
moist air. They are fueled by a different heat mechanism than other
cyclonic windstorms such as nor'easters, European windstorms,
and polar lows, leading to their classification as "warm core" storm
systems.[
Cyclone Catharina, a rare South Atlantic tropical cyclone viewed
from the International Space Station on March 26, 2004
Effects of Tropical Cyclones
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While tropical cyclones can produce extremely powerful winds
and torrential rain, they are also able to produce high waves and
damaging storm surge.
They develop over large bodies of warm water, and lose their
strength if they move over land. This is the reason coastal regions
can receive significant damage from a tropical cyclone, while
inland regions are relatively safe from receiving strong winds.
Heavy rains, however, can produce significant flooding inland,
and storm surges can produce extensive coastal flooding up to 40
km.(25 mi) from the coastline.
Although their effects on human populations can be devastating,
tropical cyclones can also relieve drought conditions.
They also carry heat and energy away from the tropics and
transport it toward temperate latitudes, which makes them an
important part of the global atmospheric circulation mechanism.
As a result, tropical cyclones help to maintain equilibrium in the
Earth's troposphere.
Polar low-
Polar low over the Barents Sea on February 27, 1987
A polar low is a small-scale, short-lived atmospheric low-pressure
system(depression) that is found over the ocean areas pole ward of the
main polar front in both the Northern and Southern Hemispheres. Polar lows
are cold-core so they can be considered as a subset of extra tropical
cyclones
In an aneroid barometer, a
partially evacuated metal
drum expands or contracts
in response to changes in
air pressure.
A series of levers and
springs translates the upand-down movement of
the drum top into the
circular motion of the
pointers over the aneroid
barometer's face.
A mercury barometer is an
accurate and relatively simple
way to measure changes in
atmospheric pressure. A basic
mercury barometer consists of a
tube filled with mercury that is
inverted, with the open end being
placed in a reservoir of mercury.
The surface of the mercury in the
reservoir represents the zero level
of the barometer. At sea level and
at normal atmospheric pressure,
the weight of the atmosphere
forces mercury 760 mm (30 in) up
a calibrated glass tube from the
zero level. As atmospheric pressure
rises and falls, so does the height
of the mercury in the tube.
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In 1643 the Italian physicist
Evangelista Torricelli invented a
barometer—an instrument for
measuring atmospheric pressure. He
filled a glass tube (sealed at one
end) with mercury and placed it with
the open end down into a container
of mercury. He observed that the
mercury level in the tube settled at
76 cm up the tube, and explained
this as caused by the pressure of the
air on the mercury in the container
forcing it up the tube. The level that
the mercury reached in the tube
varied according to different
weather conditions, indicating
variations in atmospheric pressure.
Atmospheric pressure is measured in
millibars.
What does it mean when a barometer is
rising or falling?
gravity