geo 12 chapter 8 climate

8/13/2019 Geo 12 Chapter 8 Climate

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Geography 12Chapter 8 Climate Page 1of 12(KWP)

Chapter 8 : Climate

Climate The difference between weather and climate is

simple The weather outside is the weather Climate is the long term trend of temperature and

precipitation for an area This is accumulated by data collected over the

span of a year Stations are set up around a city These stations collect data on precipitation, wind,

temperature, humidity and pressure Classification systems are used to define the globe according to climatic trends These are simple tools that can

help us understand each region, As we understand climatic

regions, we can also understandthe flora and fauna of an area.

This data is collected andpresented as a graph

The Climographgives an averageoverall image of the climate of anarea

Temperature - the red line,precipitation - bars

Climate Climatic classification systems are based on much more information than

precipitation and temperature although they are part of the equation The most popular classification is the Koppen-Geiger system P 135) First letter - temperature; second letter precipitationDont bother memorizing this chart)Koppen group and TypesA- Tropical Humid Climates

Tropical wet (Af)Tropical wet-dry (Aw)B- Dry ClimateTropical/subtropical semiarid (BSh)Tropical/subtropical and (BWk)Temperate semiarid (BSk)Temperate arid (BWk)C- Subtropical ClimatesSubtropical dry summer (Cs)

Eco region and equivalentsHumid Tropical Domain (400)Rainforest Division (420)Savanna Division (410)

Dry Domain (300Tropical/subtropical steppe division (310)Tropical/subtropical desert division (320)Temperate Steppe Division (330)Temperate Desert Division (340)Humid Temperate Domain (200)Mediterranean Division (260)


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Humid subtropical (Cf)

D- Temperate ClimatesTemperate oceanic (Do)Temperate continental, warm summer(Dca)

Temperate continental, cool summer (Dcb)

E- Boreal climatesSubarctic (E)

F- Polar climatesTundra (Ft)Ice cap (Fi)

Subtropical Division (230)Prairie Division (250)

Marine Division (240)Hot Continental Division (220)Prairie Division (250)

Warm Continental Division (210)Prairie Division (250)Polar Domain (100)Subarctic Division (130)

Tundra Division (130)

PA)The text shows a very simplified version of the classification system on page 136- pay attention to this

This is based on the Koppen system but much more simplified


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These classification systems can say much about the area including the type ofanimals that inhabit the region

Now we are going to practice making a climograph Use the data on page 167 and make climographs for each station Climate is of course influenced by the amount of 1)solar radiationthat the earthreceives a)The curvature of the earth, b)the nature of the surface of the land, c)the amountof water nearby All of these can affect the amount of solar radiation Other factors that influence climate are 2)winds and 3)currents The global wind system helps distribute air masses around the earth Hot or warm air is not as dense as cooler air


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This difference helps create the winds Air will move towards area of less density to fill in

the gap Wind systems are the result of air masses trying to

equalize or balance the pressure systems When warm air rises, it leaves a vacancy that

denser air will rush to fill The greater the difference in pressure, the strongerthe winds will be This difference is called the pressure gradient If the earth were featureless plain, the global wind

patterns would be simplified The diagram on page 142 shows how this would

look Basically, the intensity of the solar radiation on the

center (equatorial part of the earth would createlow pressure systems with the

warm moist air rushing to the topof the troposphere

As the air moved towards thepoles, it would cool, gain densityand fall creating an area of highpressure

The winds would all flow towardsthe equator to replace the risingwarm air

The earth however is notfeatureless

The seas, oceans, mountains andother land forms all combine tochange the amount of solarenergy the earth receives

This changes the temperature whichwarms or cools the air The spinning of the earth also has aninfluence The Coriolis effect also plays into theequation However, once we understand the basicsof the wind patterns, we can then chart themajor influences of the winds. This understanding allows us to chart themajor wind patterns


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The trade winds are such constant wind patterns The influence of the moisture in the air also affects the winds Since warmer air can hold more moisture, this moisture can accelerate the effects of

the wind There are also the upper atmosphere wind

systems known as the jet stream Although the jet stream is high in the upperatmosphere, its effects are felt on the surface The jet stream is like a tube of super-fast air that

flows around the globe The jet stream flows much like a river It meanders(river flow) This meander can have great influence in the surface weather The dip of the jet stream deep towards the equator has caused unsettled conditions One year it brought snow to Rome in the late Spring Another time it caused severe thunderstorms in

December in mid-west of the USA The jet stream also influences the development of

cyclones and anticyclones on the earth's surface Cyclonesare areas of low pressure systems As the air rises rapidly, it is filled in by inrushing cooler

air This generates a spin When a high pressure system anticyclone)develops,

the falling denser air displaces the air below forcingthe winds to flow out and away.

The direction of the spin is also relevant. As canbe seen in the diagram, cyclones in theNorthern Hemisphere flow anti-clockwise

While anticyclones in the Northern Hemispheregenerate a spin in a clockwise direction

In the southern hemisphere this is reversed Cyclones and

anticyclonesgenerate manyof the changesto our weatherpatterns on earth

Wind then, helps to regulate the temperatures on the surface of the earth They contribute to the mixing of the air masses and allow for the distribution of heat Another major influence is the ocean currents From England's location on the latitudes of the earth it is unusual for it to have

achieved such a strong agricultural revolution home to lush forests and large farms The ability of England to have such a vibrant agricultural capability lay in its location

to a major heat distributor


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From the map one can seethat the warm current of theNorth Atlantic Drift carrieswarm water to the coast ofthe British Isles.

When warm moist air meetscooler surface air, it generatesprecipitation

The precipitation created bythis current

The precipitation created bythis current led to the lushforests of England's past

It was also responsible for thetrademark fog of England.

The ocean currents act like theengine that drives global weather

patterns The warm currents flow north, cool

down, and sink flowing backtowards the south

Ocean currents are amazing atregulating the earths' temperature

They are able to move so quicklybecause their make-up is differentfrom the ocean around them

Ocean currents have a differentchemical composition and temperaturethat keeps them unique from thesurrounding water

Water bodies have a regulating effecton land surfaces

If the water body is constantly moving,the effect it will have on the land willdepend on whether the water is coldor warm

Warm water (as in the North Atlantic Drift) will contribute to the atmosphericmoisture which will warm the land

The west coast of many continents suffer from a lack of precipitation due to the coldtemperature of the ocean beside it.

This is the case in California, Namibia and much of the west coast of Africa, andChile

Effectively these areas become coastal deserts In the case of large lakes, the lake will modify the temperature of the surrounding

land Water takes longer to heat up and longer to cool down


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In deep lakes, the effect can lead to severe seasons I.e. Chicago, Toronto, Detroit Land is heated up by conduction, water and air is heated up by convection Large land masses like the Asian continent absorb a lot of heat during the summer

months This results in many low pressure systems drawing wind in from the south Pacific The insolation continues to feed this as long as the earth's tilt is in the optimumposition The inability of land to retain heat means that in the winter, the land mass cools very

quickly This rapid cooling draws strong winds from the cooler water bodies This changes the direction of the winds

and creates the phenomenon known asthe monsoon.

The summer monsoons create torrentialrainfall as the air is laden with moisture

This seasonal change occurs everywherebut is more pronounced in Asia

Asia has a distinct monsoon reasonwhen the locals know what to expect.

Altitude As we rise in the atmosphere the temperature has a tendency to decrease The rate of change in temperature in the atmosphere is called the environmental

lapse rate The temperature change begins at the ground (or sea level) and continues on to the

top of troposphere

The rate at which it changes is the environmental lapse rage. In general, the ELR is based on the calculation of 6.4C for every 1000 m Understanding this calculation one can determine the degree to which the

temperature will decreased on a mountain as one rises on said mountain


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Does the environmental lapse rate ever change? The ELR changes based on location, time or year, cloud cover, which are all based on

solar radiation. There are three factorswhich can affect the ELR These are: Heating and cooling of the lower atmosphere. This can be affected by the type of

ground cover, the ability of the ground to absorb solar radiation and other factors The advection of cold and warm air at different altitudes. Air masses can affect the

ELR by increasing the cooling factor or slowing it down Advection of a new air mass with a different ELR. The conflict between two air

masses will influence the ELR.

Sensible Heat Flux The day is at its warmest in the mid-afternoon, when both the surface and the lower

atmosphere have warmed. At night, the surface can cool more rapidly than the air above creating a temperature The warming is the sensible heat flux Sensible heat flux is the process where heat energy is transferred from the Earth's

surface to the atmosphere by conduction and convection The heat energy then can move horizontally by atmospheric circulation Sensible heat flux can be expressed by the amount of heat transmitted per unit of

area per unit of time The SHF is useful in the water cycle, the energy cycle, weather forecasting and in

understanding global climate change Both air currents and ocean currents move heat Energy is stored as "latent heat" in the

atmosphere In the surface waters of the ocean it is

stored as "sensible heat" Sensible heat is the energy associated

with the temperature of a body; it isgreater in a warm bod than a cold one.Warm water that is heated in the tropicscan cooled in high latitudes bringssensible heat pole ward

The density of the air at the earth'ssurface allows it to absorb much more

energy As the air gets "thinner" the higher it

goes, the spreading of the moleculesmeans the air is cooler.

Mountains then, have a direct influenceon the atmosphere heat

Air masses that meet mountains areforced to rise

Diagram of latent heat transport:

the transport of latent heat plays an important role in

the redistribution of heat on the surface of the earth

Cloud carries itsheat to higherlatitudes

Cloud replaces latent heat whenit precipitates in the higherlatitudes

Evaporation leads to cloudformation in the tropics andsub-tropics thus capturing heat


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As air parcels move up a mountain, they encounter less resistance As the air expands, it cools The air molecules themselves do not lose any energy (heat) The cooling occurs due to the thinning of the air Air molecules are father apart This effect increases with altitudes The rate at which it cools is called the Dry Adiabatic Lapse Rate For unsaturated air) No heat is lost from the air molecules themselves (no heat lost) The calculation is approx. 10C for every 1000 mof vertical rise As the air mass is further dissipated, its ability to hold water vapor decreases. TheWet Adiabatic Lapse Rate For saturated air)describes the decrease in

temperature when water vapor has expended much of the energy in the moleculesforcing condensation ofsome form

The text calculates theWALR at3 C for every1000 meters

When the air mass loses itsenergy after condensationat the mountain top, the airmass still has its "mass"

When it reaches theleeward side of themountain that air mass will rush down themountain side

Since the mass as lost its moisture and hence,its energy, it is a dry air mass

These unseasonably strong dry winds areknown in Canada as a Chinook

In Switzerland the Fohn, Germany the Sirocco In any case these winds can cause weather

challenges on the land below the mountain A strong Chinook can make snow

one foot deep almost vanish in oneday

Chinook winds have been observedto raise winter temperature, oftenfrom below -20C (-4F) to as high as

10-20C (50-58

F) for a hours or

days, then temperatures plummet totheir base levels

Local influences As was mentioned before, there are many other factors that can influencetemperature Proximity to a body of water


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Amount of urban growth concrete) Height of buildings These can be all influence the temperature and thereby, the weather Proximity to water is a great influence Land heats up quickly and cools down quickly Water on the other hand, takes much longer to heat up since the rays of the sun

penetrate much deeper. Water also retains this heat energy longer as well, releasing it slowly PA) Sea breezes are the result of this imbalance

Atmospheric Stability Air is in stable equilibriumwhen after

being lifted or lowered, it tends to returnto its original position - resists upward anddownward air motions

Air Parcel- balloon like blob of air As air rises its pressure decreases and it

expands and cools As air sinks pressure increases and it is

compressed and warms

Adiabatic Process If an air parcel expands and cools, or compresses and warms, with no interchange of

heat with its outside surroundings the situation is called an adiabatic process Dry Adiabatic lapse rate - 10C per 1km or 5.5 F per 1000 feet (applies to

unsaturated air)

Expand-s andcools

Air parcels

Compres-ses andwarms


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Moist adiabatic lapse rate - ~6C per 1 km or 3.3 F per 1,000 ft (applies to saturatedair). Not a constant. Varies greatly. This number is used to keep things simple.

Determining stability Determine stability by comparing the temperature of a rising parcel to that of its

surrounding environment It is colder than its environment it will be denser (heavier) and tend to sink back to its

original level. This is called stable air because the parcel resists moving away from itsoriginal position

If the parcel is warmer (less dense) than its environment, it will continue to rise until itreaches the same temperature of its environment. This is called unstable air becausethe parcel continues to move away from its original position

Stable air Environmental Lapse Rate- Rate at which the air temperature of the environment

would be changing if we were to climb upward into the atmosphere Absolutely stable- the lifted parcel of air is colder and heavier than air surrounding it

(its environment) Stable air strongly resists upward vertical motion, it will, if forced to rise, tend to

spread out horizontally Atmosphere is stable when the environmental lapse rate is small- when there is

relatively small difference in temperature between the surface air and the air aloft The atmosphere stabilizes as the air aloft warms or as the air near the surface cools

(a)Lifted, unsaturated air at each level is

colder and heavier than the air around it. If

given the chance, the parcel would return to

its original position, the surface.

(b)Lifted, saturated air at each level is colder

and heavier than the air around it. If given

the chance, the parcel would return to its

original position, the surface.

Temperature of lifted

unsaturated air (C)

(dry rate)

Temperature of lifted

unsaturated air (C)

(moist rate)

Temperature of

environment (C)Temperature of

environment (C)


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Unstable air Atmosphere is unstable when the air

temperature decreases rapidly as wemove up into the atmosphere

Absolutely unstable atmosphere - whenconsidering both moist and dry air - therising air is warmer than theenvironmental air around them

Atmosphere becomes unstable when: Daytime solar heating of the surface An influx of warm air brought in the

wind near the surface Air moving over a warm surface

Convection and Clouds Some areas of the earth surface absorb

more sunlight than others, and thus heatup more quickly (Discuss examples)

Thermal- a hot bubble of air that breaksaway from the surface and rises, expandingand cooling as it ascends

As a thermal rises, it mixes with cooler,drier air aloft and gradually losses itidentity. But, if it cools to its saturationpoint, the moisture inside will condenseand the thermal becomes a cumulus cloud

geo 12 chapter 8 climate

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