DETERMINANTS OF GLOBAL CLIMATE PATTERNS
by Antonio C. Antonio
February 7, 2015
Have you even been asked this innocent question: “Will
climate change possibly bring snow to the Philippines?” I would rather leave the answer to your
fertile imagination.
There are two determinants of global climate patterns. These are temperature and precipitation which
are factors that determine climate.
Precipitation is defined as any form of water, liquid or solid, falling
from the sky. It includes rain, sleet,
snow, hail and drizzle plus a few less common occurrences such as ice pellets,
diamond dust and freezing rain. On the
other hand, temperature is the degree or intensity of heat present in a
substance or object, especially as expressed according to a comparative scale
and shown by thermometer or perceives by touch.
While precipitation and temperature are the determinants of
climate, the following factors determine global climate:
THE SUN’S RAYS AND THE SPHERICAL EARTH – The sun’s rays does
not reach the Earth uniformly. The Earth
is a sphere. The Earth’s surface is heated more at the equator than the poles
because the sun’s rays strike the equator at right angles to the surface and
maximum energy intensity is received. At
the poles, the sun’s rays are received at an oblique angle and are spread out
over a much greater area, hence lower energy is received per unit area. The obliqueness of the rays also means that
they have to travel a longer distance through cloud cover and atmosphere. This will further reduce the amount of energy
actually heating the Earth’s surface.
ELLIPTICAL ORBIT AND THE EARTH’SROTATION AROUND THE SUN – The
Earth rotates around the sun at the rate of 365.25 day/revolution. The orbit of the Earth’s rotation around the
sun is an ellipse. At any given point in
time, the Earth is located at a particular distance from the sun. This distance determines the amount of energy
received by the surface. The Earth is
nearest the sun at perihelion, observed ar abut January 3. The aphelion, when the Earth is farthest the
sun occurs at about July 4. The average
Earth-sun distance occurs about April 4 and October 5. The amount of solar radiation intercepted by
the Earth at perihelion is about 7% higher than aphelion.
GLOBAL TILT AND THE EARTH’S AXIS – As it rotates around the
sun, the Earth is tilted on its axis at an angle of 23 degrees. The tilt leads to uneven heating of the Earth
and produces seasons and climate patterns around the globe. Seasonal tilting of the Earth’s axis means
that there is no sunlight at the poles during much of the winter. In the tropical region, an almost uniform
amount of solar energy is received by the surface. Likewise, minimal variation in temperature is
experienced in the tropics. This is
because the position of the tropical zone and the tilt of the Earth’s rotation
are both at 23.5 degrees. Temperature
variation increases with increasing latitude from the equator. In temperate region, there are four distinct
season, therefore, winter, spring, summer, and autumn. In the tropics, only two seasons are
identified: dry and wet.
ATMOSPHERIC CIRCULATION – When the surface is heated, air
above it is also heated, and it becomes light and rises up. As warm air rises, it encounters lower
atmospheric pressure and expands, spending some of its energy. The decrease in the internal energy of the
air parcel cools it at a rate of 10 degrees/1000 meters. When it sinks, the air mass warms at the same
rate. The rate of decrease in
temperature of the rising air mass is called the dry adiabatic lapse rate. In most air, water vapour will condense as it
cools and release latent heat to the surrounding air. The heat released partially counteracts
cooling of the air. The adiabatic lapse
rate for moist air is 6.0 degrees/1000 meters.
As the lighter warm air rises and is replaced by cooler heavier air, a
vertical convection current develops, stirs the atmosphere and transport heat
from one area to another. Water vapour
carries into the atmosphere by rising convection current transports large
amounts of energy and plays an important role in the redistribution of heat
from low to high altitudes and from the oceans to continental land masses. If temperature is low enough, it will
condense to form water droplets and precipitation will take place. The heat released when water vapour condenses
radiates into space. The resulting
cooler, drier air becomes denser, sinks, and creates an area of high pressure. At this air mass flows across the Earth’s
surface, it picks up heat and moisture and begins to rise again. The resulting convection cells circulate air,
heat, and moisture both vertically and from place to place in the troposphere,
leading to different climates. Mountains
and other geographical barriers also affect the circulation of air and
water. As the moving air mass encounters
a mountain barrier, air will be forced to rise following the slope of the
mountain. As the moisture-laden air mass
from the windward side of the barrier rise, it cools and the water vapour
condenses and falls as rain. A cold air
mass is heavy and will tend to sink but is forced to rise by the prevailing
wind. When the cold, dry air mass
reaches the summit, it will descend on the leeward side of the mountain. As it goes down, it warms up and picks up moisture
along the way. Warm air has a higher
capacity to hold water. Upon reaching
the base of the mountain, it will have warmed up enough to again rise but it
carries by the prevailing wind to another place where it will release water as
precipitation, leaving the leeward side of the mountain barrier to be
relatively dry.
PLACEMENT OF CONTINENTS AND OCEANS – The interior of a
continent is usually drier that its coast simply because the interior is
farther away from the major site of water evaporation. Maritime (coastal) climates are also less
variable than continental (interior) climates because the high heat capacity
(amount of energy needed to change the temperature of 1 degree centigrade) of
water compared to land, moderates coastal temperatures.
OCEAN CURRENT – Ocean current also plays a major role in
transferring heat over the surface of the Earth. In large ocean basins, cold water tends to
move toward the tropics along the western coast of the U.S. continent. The cold Humboldt current moving north along
the coast of Chile and Peru is partly responsible for the presence of deserts
along the west coast of South American rift to the equator. Conversely, the warm Gulf Stream emanating
from the Gulf of Mexico carries mild climate far to the north into western
Europe. Current also helps mix ocean
waters and redistribute nutrients needed by aquatic organisms. Along some steep, western coasts of
continents, almost constant trade winds blow offshore, pushing surface water
away from land. This outgoing surface
water is replaced by upwelling of nutrient-rich, cold bottom water. Changes in prevailing winds can change the
temperatures of surface waters, weaken or alter ocean currents, suppress
upwelling and trigger weather changes over at least two-thirds of the
globe. (Source: “Ecosystem Structure and Dynamics”: Medina,
Zafaralla, Sierra, Cuevas, Macandog and Cervancia, 1999)
If and when the innocent question (therefore, “Will climate
change possibly bring snow to the Philippines?”) is asked of you, you will now
have more intelligent facts to use in answering it… the determinants of global
climate patterns.
Just my little
thoughts…
(Please visit,
like and share Pro EARTH Crusaders on Facebook or follow me at http://antonantonio.blogspot.com/.)
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