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LECTURE 7 : SUNEARTH RELATIONSHIPS

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LECTURE 7 : SUN-EARTH RELATIONSHIPS & SEASONS P ART 2. THE SUN, EARTH & THEIR EFFECTS ON SEASONS ... Sun is overhead at Tropic of Capricorn in Dec 21 Winter Solstice ... – PowerPoint PPT presentation

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Title: LECTURE 7 : SUNEARTH RELATIONSHIPS


1
LECTURE 7 SUN-EARTH RELATIONSHIPS SEASONS
P ART 2
  • THE SUN, EARTH THEIR EFFECTS ON SEASONS
  • FACTORS AFFECTING INSOLATION RECEIVED ON EARTH
    ITS INFLUENCE ON SEASONS
  • THE SEASONS

2
  • THE TRANSFORMATION OF ENERGY
  • SHORTWAVE RADIATION (SOLAR ENERGY) is
    transformed into all other forms of energy once
    it is absorbed.
  • For example, air molecules and water
    droplets/vapor in the atmosphere absorb the
    incoming solar energy and once absorbed, changes
    it to SENSIBLE HEAT ENERGY warming that part of
    the atmosphere, resulting in TEMPERATURE
    INCREASE. Differences in distribution of solar
    energy will result in different areas being warm
    and cold.
  • Hot Cold areas then give rise to differences
    in PRESSURE (POTENTIAL ENERGY) which in turn
    creates AIR FLOWS or WIND SYSTEMS (with air
    masses flowing from High Pressure areas into Low
    Pressure areas). WINDS are a form of KINETIC
    ENERGY.
  • When solar energy heats up the seas,
    SENSIBLE HEAT
    ENERGY is created in the
    form of warm waters.
  • Warm waters turn to EVAPORATION, a form
    of LATENT
    HEAT ENERGY.
  • As water vapor evaporates into the atmosphere,
    it forms
    CLOUDS (POTENTIAL ENERGY).

3
  • In the clouds, there are POSITIVE and NEGATIVE
    CHARGES, which collide giving out LIGHTNING (a
    form of ELECTRICAL ENERGY).
  • Lightning is accompanied by THUNDER (a form of
    SOUND ENERGY).
  • When PRECIPITATION (rain, snow, hail, mixed)
    occurs, it changes to KINETIC ENERGY.
  • Rain flows into rivers and river flow is another
    form of KINETIC ENERGY.
  • PHOTOSYSNTHESIS when solar energy is fixed
    (absorbed) by green plants, it changes to
    CHEMICAL ENERGY.
  • Photosynthesis is the most important natural
    process (as only green plants and a limited
    number of photosynthetic bacteria are capable of
    transforming solar energy into chemical energy -
    FOOD) changes solar energy into CHEMICAL ENERGY.
  • This chemical energy is then passed on to
    animals and humans when plants are consumed.

4
THE OBSESSIVE VEGETARIAN
FRUIT FLY
5
A PORTION OF THE ELECTROMAGNETIC SPECTRUM OF
RADIANT ENERGY
  • TOTAL SOLAR RADIATION
  • 8 Ultra-violet, X-ray Gamma-ray
  • 47 Visible Light
  • 45 Infrared

6
A SIMPLIFIED ENERGY BUDGET OF THE EARTH
INCOMING SHORTWAVE RADIATION
OUTGOING LONGWAVE RADIATION
7
  • THE SUN, EARTH THEIR EFFECTS ON SEASONS

S
N
  • INSOLATION RECEIVED ON EARTH IS UNEVENLY
    DISTRIBUTED
  • HEAT SOURCE AREAS RECEIVING MORE ENERGY THAN
    THEY GIVE OUT
  • HEAT SINKS AREAS GIVING OUT MORE ENERGY THAN
    THEY RECEIVE
  • HENCE, WOULD SOURCES GET HOTTER SINKS GET
    COLDER?
  • NO BECAUSE THERE IS ENERGY TRANSFERS TAKING
    PLACE CONTINUOUSLY
  • HENCE, AS A WHOLE, EARTH MAINTAINS ITS ENERGY
    BALANCE

8
  • FACTORS AFFECTING INSOLATION RECEIVED ON EARTH
    ITS INFLUENCE ON SEASONS
  • SOLAR AND UNIVERSAL FACTORS
  • SOLAR OUTPUT - During periods of Solar Maximum,
    Solar Minimum, Sunspots and Long Term Solar
    Cycles, solar output varies.
  • EARTH'S ORBIT ROUND THE SUN - Earth's orbit round
    the sun is elliptical, i.e. OVAL SHAPED.
    PERIHELION (Jan 3) - earth is 91.5 million miles
    away from the sun APHELION (July 4) - earth is
    94.5 million miles away.
  • SOLAR ECLIPSE, LUNAR ECLIPSE INFLUENCE OF OTHER
    PLANETS

9
  • (2) ATMOSPHERIC FACTORS
  • (i)CLOUD COVER
  • In Equatorial areas, due to high amount of cloud
    cover, total annual solar energy received is
    about 140 kilocalories/cm2/year.
  • In contrast, areas in deserts (Sahara) receive
    more than 200 kilocalories/cm2/year.
  • Hence, daytime temperatures in Equatorial areas
    seldom exceed 90 o F but in the Sahara desert, lt
    120 o F is common.
  • (ii)AMOUNT OF AIR POLLUTION PARTICLES
  • (iii)THICKNESS OF ATMOSPHERE
  • Thick at the Equator Tropopause (line between
    troposphere stratosphere) is about 11 miles
  • Moderate at Mid-latitudes Tropopause is about
    8 miles
  • Shallow/Thin at the Poles - Tropopause is only
    about 5 miles

10
(3) EARTH FACTORS (i)EARTH'S CURVED SURFACE -
Equatorial areas (Direct Sunlight) typically
receive 2.5 times more solar energy than polar
areas (Oblique Sunlight). (ii)SEASONS - In
Summer, all areas receive more sunlight (with the
Sun positioned overhead at most times) compared
to in Winter (all areas receive much less
sunlight which come in at low angles). In the
Arctic Circle, summer means three months of
sunlight (i.e. 24 hours a day) while Winter means
three months of complete darkness.
(iii)DAYLENGTH NIGHTLENGTH - In June, the
North Pole receives 500W/m2 per day (24 Hours
Daylight) but the South Pole receives 0 W/m2 per
day (0 Hours Daylight). In December, the South
Pole receives 550W/m2 per day (24 Hours daylight)
- more than North Pole in June because Earth is
closer to Sun during Perihelion (January 3). The
North Pole now receives 0 W/m2 per day (0 Hours
Daylight). (iv)EARTH SURFACE CHARACTERISTICS -
Rate of Reflection Forest - 20 Savana - 13
Desert - 28 Asphalt Road - 5 Dark Soils -
5-15 Snow (fresh) - 70-75 Snow (old) - 45-70

11
HOW INSOLATION RECEIVED AT THE EARTHS SURFACE
VARIES
CURVATURE EFFECT
EARTHS TILT EFFECT
THICKNESS OF ATMOSPHERE EFFECT
SURFACE CHARACTERISTICSEFFECT
EARTHS ROTATION EFFECT
12
Sun is overhead at Tropic of cancer in June 21
Summer Solstice Areas in Northern Hemisphere
Hot in middle of the year cold at the end of
the year
Seasons near the Equator is the same all year
round - All Summer
Sun is overhead at Tropic of Capricorn in Dec 21
Winter Solstice Areas in Southern Hemisphere
Cold in middle of the year Hot at the end
13
THE SEASONS
90 o
  • WHAT IS MEANT BY SEASONS?
  • Seasonality refers to
  • the variation in the temperature dividing the
    year into 4 seasons of Spring, Summer, Fall
    (Autumn) Winter
  • the seasonal variation of the Suns position
    above the horizon
  • the changing daylengths during the year
  • Seasonal variations are a response to the Suns
    altitude which is the angle between the horizon
    and the Sun
  • At sunrise or sunset, the Sun is at the horizon
    so its altitude is

0 o
During the day, when the Sun reaches halfway
between the horizon and directly overhead, its
altitude is
45 o
90 o
When the Sun is directly overhead, or ZENITH, its
altitude is
45 o
0 o
0 o
14
The Sun is directly overhead only at the SUBSOLAR
POINT the point where insolation is at
maximum At all other points, the Sun is at a
lower angle, solar insolation is difuse The
Suns declination is the latitude of the
subpolar point Declination annually migrates
through 47 o of latitude, moving between the
Tropic of Cancer (23.5 o N) to the Tropic of
Capricorn (23.5 o S) Hence, the subpolar point
reaches only 1 place in the United States
- only Hawaii (located between latitudes 19
o N and 22 o N)
15
WHAT CAUSE THE SEASONS?
  • REVOLUTION Earths orbit round the Sun of
    365.24 days (66,660 mph)

16
WHAT CAUSE THE SEASONS?
(2) ROTATION Earth rotating on its axis of 24
hours a day (1041 mph at the Equator)
17
WHAT CAUSE THE SEASONS?
(3) TILT Earths axis is tilted at an angle of
23.5 o from a perpendicular to the Plane of the
Ecliptic
Earths Tilt of 23.5 o to the Plane of the
ecliptic
Plane of the ecliptic
18
WHAT CAUSE THE SEASONS?
(4) AXIAL PARALLELISM Earth remains in a fixed
alignment, pointing at Polaris directly overhead
at the North Pole throughout the year
North Pole Also pointing at Polaris
19
WHAT CAUSE THE SEASONS?
  • (5) SPHERICITY Earth appears as an oblate
    spheroid (geoid) to the Suns parallel rays
  • Produces uneven distribution of solar radiation
  • Produces pressure differences
  • Produces different seasonal winds e.g. Monsoons

END THANK YOU
20
THE SEASONS IN ASIA INFLUENCE OF MONSOONS
THE NORTH-EAST MONSOON SEASON IN MALAYSIA HAS
PROFOUND INFLUENCES ON BOTH THE PHYSICAL
GEOGRAPHY (IN TERMS OF CLIMATE, HYDROLOGY,
VEGETATION, SOILS AND GEOMORPHOLOGY) AND THE
HUMAN GEOGRAPHY (AGRICULTURE, TOURISM,
TRANSPORTATION, BUSINESS, INDUSTRY, SETTLEMENT,
POPULATION ETC) OF MALAYSIA. LP LOW PRESSURE
HP HIGH PRESSURE WINDS IN NORTHERN HEMISPHERE
NORTH-EAST MONSOON WINDS WINDS IN SOUTHERN
HEMISPHERE NORTH-WEST MONSOON WINDS
21
  • THE SOUTH-WEST MONSOON SEASON
  • THESE WINDS ARE NOT AS INFLUENTIAL AS THE
    NORTH-EAST MONSOON BECAUSE MALAYSIA IS LARGELY
    SHELTERED FROM THE EFFECTS OF THE FORMER BY THE
    INDONESIAN ISLAND OF SUMATERA AND OTHERS WINDS
    IN THE SOUTHERN HEMISPHERE ARE SOUTH-EAST
    MONSOON WINDS
  • WINDS IN THE NORTHERN HEMISPHERE ARE SOUTH-WEST
    MONSOON WINDS
  • THE WINDS CHANGE DIRECTIONS AS THEY MOVE FROM
    THE SOUTHERN HEMISPHERE TO THE NORTHERN
    HEMISPHERE BECAUSE OF THE INFLUENCE OF THE
    CORIOLIS EFFECT, I.E. THE DEFLECTION EFFECT DUE
    TO EARTH'S ROTATION.

22
CHANGES IN SEASONS is perhaps best illustrated by
the monthly temperature change in a place. Here
in Anderson Lake, Alaska, the temperatures are
below zero at the beginning and end of the year -
i.e. Winter in the Northern Hemisphere. Summer in
Fairbanks, as in all other places North of the
Equator, occurs in the middle of the year - i.e.
peaks in June. Hence, Anderson Lake and all
other places in the northern hemisphere have an
annual temperature graph shaped like a "Hill".


23
MEMPHIS - The annual variation of monthly
temperatures for Memphis shows that the city also
has a "hill" shaped graph. However, Memphis is
located further south compared to Fairbanks.
Hence, the winters are milder and no single month
experiences average temperatures below zero.
However, that is not to say Memphis never
experiences any Day with temperatures below zero.
There may be days in the month of December or
January with sub-zero temperatures but this
happens only on the odd day or two, not enough to
plunge the average monthly temperature for
December and January below zero.


24
SINGAPORE is located very close to the Equator.
Hence, like many other places close to the
Equator, monthly temperatures are fairly stable
and do not vary much. This gives rise to a
temperature graph shaped like an almost "Straight
Horizontal Line". For most months, Singapore
experiences temperatures ranging from 26 to 27
degrees Celcius.
25
SYDNEY, AUSTRALIA is located in the Southern
Hemisphere. Temperatures are mild and very
favorable as there are no extremes. The monthly
temperature graph is shaped like a "Valley"
instead of the "Hill" pattern in the northern
hemisphere. This is because the seasons are
reversed in the southern hemisphere. Aussies
typically celebrate their Christmas on the
beaches (having BBQs) in Summer when Americans
are freezing with snow! On the other hand,
Aussies have Winter in the middle of the year.
Spring (September) and Fall (April) for the
Aussies are also reversed. When people in Memphis
are experiencing Fall (September), people in
Sydney are having Spring and vice versa.
26
PUNTA ARENAS is located at the tip of South
America, almost
near to the
South Pole. Because of its southerly position,
temperatures are severe and many months have
average temperatures below zero. Again, we see
the "Valley" shaped graph indicating Summer in
the beginning and end of the year but Winter in
the middle of the year.
27
END THANK YOU
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