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Weather and Climate
BY URJA, CHANI, MEGHNA AND AYAAN
Vocabulary
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Adiabatic cooling/heating The rate of cooling (by expansion) as an air parcel rises. It is
approximately 1 degrees Celsius per 100 meters. It is also the rate of heating (by
compression) as an air parcel descends.
Air mass A large body of air that has similar temperature, pressure and moisture
properties.
Anticyclone High pressure system in which air descends to give calm conditions and
clear skies. Associated with summer heat waves and winter frosts and fogs.
Atmosphere The envelope of air surrounding the Earth and bound to it by gravity.
Atmospheric pressure: Pressure (force per unit area) exerted by the atmosphere on any
surface by virtue of its weight.
Vocabulary
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Climate Long-term (50 year) weather averages.
Continental climate A climate with a high temperature range away from the
influence of the sea. Winters will be colder and summers warmer compared to
a coastal location for the same latitude.
Areas of Low Pressure/Depression (cyclone, low, low-pressure area) Area in
the atmosphere in which the pressures are lower than those of the surrounding
region at the same level. In its development a depression usually has the
following phases. A wave (young) depression forms and moves along a front.
Mature depressions have well-developed warm sectors and both cold and
warm fronts. An occluded depression is that within which there has developed
an occluded front.
Vocabulary
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Evaporation The physical process by which a liquid or solid substance is transformed to a
gas; the opposite of condensation.
Fog Saturated air with visibility below one kilometre. Fog differs from cloud only in that the
base of fog is at the Earth's surface while clouds are above the surface.
Front The meeting point between two air masses of different density. Since the
temperature is the most important regulator of the atmosphere density, a front almost
invariably separates air masses of different temperature. When warmer air replaces the
colder, it is a warm front, and a front is a cold one when the opposite occurs.
Humidity Water vapor content of the air.
Maritime climate A climate with a low temperature range influenced by proximity to the
sea. Winters will be warmer and summers cooler compared to a continental location for
the same latitude.
Vocabulary
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Precipitation Any of all of the forms of water particles, whether liquid or solid, that fall
from the atmosphere and reach the ground. The forms of precipitation are: rain, drizzle,
snow, snow grains, snow pellets, diamond dust, hail, and ice pellets.
Prevailing wind The most common wind direction for a particular location.
Rain Shadow The dry region on the leeward side of a mountain (the side sheltered from
the wind).
Relief rainfall Formed when air is forced to rise over relief features such as hills or
mountains. Cooling and condensation occurs as the air rises.
Seasonality Periodic fluctuations in the climate related to seasons of the year e.g. wet
winters, drier summers.
Smog A word currently used as a synonym for general air pollution. It was originally
created by combining the words "smoke" and "fog."
Vocabulary
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Synoptic chart A weather chart reflecting the state of the atmosphere over a large area at a given moment.
Temperature A physical quantity characterizing the mean random motion of molecules in a physical body. In
other words, it is a measure of the degree of hotness or coldness of a substance.
Temperature range Maximum minus the minimum temperature for a particular location.
Warm front The forward edge of an advancing warm air mass that is rising over cooler air in its path.
Warm sector The zone of warm air within a depression.
Water vapor Water substance in vapor (gaseous) form; one of the most important of all constituents of the
atmosphere.
Weather The state of the atmosphere, mainly with respect to its effects upon life and human activities. As
distinguished from climate, weather consists of the short-term (minutes to about 15 days) variations of the
atmosphere state.
Wind movement of air caused by changes in temperature and air pressure. Winds are always identified by the
compass direction from which they blow.
Precipitation example
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The science of monitoring and studying the atmosphere and predicting its
weather and climate is called meteorology
Seasons
Seasons
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Winter- It is the coldest season of the year in polar and temperate
climates. It is caused by the axis of the Earth in those hemispheres being
positioned away from the sun
Seasons
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Spring- Spring occurs after the winter season, and before summer. This is
the season where vegetation appears for the northern hemisphere, which
is march to may, and vegetation for the southern hemisphere happens in
September to November
Seasons
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Summer- Is the warmest season of the year, it occurs in the northern
hemisphere from June to August. and in the southern hemisphere during
December and February.
Seasons
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Monsoon- Monsoon is a term that is used in meteorology to signify a
seasonal reversal of wind direction.
Autumn
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Autumn- The season after summer and before winter. Which occurs in the
northern hemisphere from September to November, and in the southern
hemisphere from March to May.
Climate
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Climate- it is the average weather in a place over many years. Weather
changes daily whereas climate changes over the years.
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In an average year the climate in a tropical rainforest is very humid due to
all the rainfall. These types of climates are found near to the equator
because there is direct sunlight.
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The climate in tropical desserts are very dry and hot, and has hardly any
rainfall. October is recorded as the hottest month over the years.
Case Studies
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During December 2010 winds from the north east brought cold arctic air and snow. Scotland
and North East England were significantly affected, with snow 50 cm deep in places.
Temperatures were mainly below 0°C, making it the coldest December in the last 100 years.
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The impacts were:
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Roads were closed. People were stranded in their cars overnight on the M8 and A9 in
Scotland.
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Airports closed, including Heathrow and Gatwick, disrupting travel plans over Christmas.
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Schools closed.
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On 20 December the AA reported its busiest-ever day because of car breakdowns.
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More people than usual were admitted into hospital because of accidents and falls.
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Emergency services and local authorities were all put under pressure.
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After areas thawed, there were problems with burst water pipes. In Northern Ireland
40,000 homes were without water
Africa
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Africa is at risk from climate change. Observed temperatures have
showed a warning since 1960s suggesting that the annual temperature in
the region will rise by 3.4 degree Celsius.
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This will cause the annual rainfall to decrease, causing higher rainfall in the
northern region.
Mozambique: 2007 floods and cyclone
“The magnitude of the cyclone and floods (together with drought
conditions in the south of the country, which have not been part of the
UN humanitarian response) all point to the effects of global warming.
These natural disasters are growing more frequent and more severe with
time, highlighting the importance of national preparedness to reduce
the vulnerability of the population to such events and minimize their
impact.”
By the end of February 2007, Mozambique was reeling from the double
impact of two disasters. While Zambezi and Save rivers were already
flooded, a Category four cyclone brought more rain and destroyed
southern coast.
Tebunginako Village
“The village of Tebunginako on the island of Abaiang is a barometer for what Kiribati can expect in the
future. The community has had to relocate due to the effects of severe coastal erosion and saltwater
intrusion. These impacts are already felt on the atolls of Kiribati and will be exacerbated by the effects
of climate change.”
Over the past 40 year the sea level has risen, storm surges have become more powerful and tides more forceful.
Eventually the erosion was so great that the village had to be abandoned.
The access salt is effecting the area. The fresh water milkfish, that once fed the village is long gone. The pant
life is fatally overdosing on salt.
Each year villagers head further into the island to find fresh food and water, but the island can only go back so
far.
”It is very difficult to find food these days,” Mr Maroieta says. ”It makes us feel sad that there is nothing left of
our village. This is the place of our ancestors and we feel threatened and vulnerable.”
Cyclones
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Cyclones - a cyclone is an area of closed, circular fluid motion rotating in
the same direction as the Earth. Most large-scale cyclonic circulations are
centered on areas of low atmospheric pressure
Anti- Cyclones
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Anticyclones- a large-scale circulation of winds around a central region of
high atmospheric pressure, clockwise in the Northern Hemisphere,
counterclockwise in the Southern Hemisphere
Wind Currents
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Wind Currents - Winds are named by the direction from which they blow. The
globe is encircled by six major wind belts, three in each hemisphere. From pole
to equator, they are the polar easterlies, the westerlies, and the trade winds.
All six belts move north in the southern summer and south in the northern
winter.
Wind Currents
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Wind Currents - Winds are named by the direction from which they blow.
The globe is encircled by six major wind belts, three in each hemisphere.
From pole to equator, they are the polar easterlies, the westerlies, and the
trade winds. All six belts move north in the southern summer and south in
the northern winter.
The Green house affect
Types of Rainfall
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Types of Rainfall -
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convection rainfall: Convectional rainfall occurs when the energy of the
sun (or insolation) heats the earth’s surface and causes water to
evaporate changing to water vapor
Relief rainfalls
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Relief rainfall usually takes place around coastal areas where a fleet of
hills runs along to the coast. When wet onshore wind from the sea meet a
mountain, hill and barrier, it is forced to rise along the slope and cools.