geo 12 chapter 8 climate
TRANSCRIPT
-
8/13/2019 Geo 12 Chapter 8 Climate
1/12
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)
-
8/13/2019 Geo 12 Chapter 8 Climate
2/12
Geography 12Chapter 8 Climate Page 2of 12(KWP)
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
-
8/13/2019 Geo 12 Chapter 8 Climate
3/12
Geography 12Chapter 8 Climate Page 3of 12(KWP)
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
-
8/13/2019 Geo 12 Chapter 8 Climate
4/12
Geography 12Chapter 8 Climate Page 4of 12(KWP)
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
-
8/13/2019 Geo 12 Chapter 8 Climate
5/12
Geography 12Chapter 8 Climate Page 5of 12(KWP)
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
-
8/13/2019 Geo 12 Chapter 8 Climate
6/12
Geography 12Chapter 8 Climate Page 6of 12(KWP)
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
-
8/13/2019 Geo 12 Chapter 8 Climate
7/12
Geography 12Chapter 8 Climate Page 7of 12(KWP)
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
-
8/13/2019 Geo 12 Chapter 8 Climate
8/12
Geography 12Chapter 8 Climate Page 8of 12(KWP)
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
-
8/13/2019 Geo 12 Chapter 8 Climate
9/12
Geography 12Chapter 8 Climate Page 9of 12(KWP)
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
-
8/13/2019 Geo 12 Chapter 8 Climate
10/12
Geography 12Chapter 8 Climate Page 10of 12(KWP)
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
-
8/13/2019 Geo 12 Chapter 8 Climate
11/12
Geography 12Chapter 8 Climate Page 11of 12(KWP)
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)
-
8/13/2019 Geo 12 Chapter 8 Climate
12/12
Geography 12Chapter 8 Climate Page 12of 12(KWP)
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