Global climate factors

1. INTRODUCTION TO
GLOBAL CLIMATE

2. Definitions:
Climate is integration in time of the physical states of the
atmospheric environment, characteristics of a certain
geographical region.
Weather is the momentary state of atmospheric
environment at a certain location
Climate can be called the integration of time of weather
condition.
Climate has four major elements:-
1. EARTH – soil
2. WATER – humidity
3. FIRE – sun and temperature
4. AIR – wind

3. WHAT IS CLIMATOLOGY ?
The scientific study of climate is called climatology.
• The purpose of studying climatology is to achieve maximum
human comfort both indoor as well as outdoors by utilizing
maximum natural energy and resources.
• The earth receives almost all its thermal energy from sun in
the form of radiations and sun’s rays is the most dominating
factor.
• Heat received at a given point on earth depends on angle of
incidence, atmospheric conditions (haze, clear sky), length of
the day.

4. The earth is divided into
three major climatic zones
•Tropical,
•Temperate,
•Polar
Due to the tilted
position, the area
receiving the maximum
intensity moves north
and south, between the
tropic of Cancer and the
tropic of Capricorn. This
is the main cause of
seasonal changes

5. WEATHER VS CLIMATE
WEATHER CLIMATE
• Refer to small area
• Short Period
• Change from time to time
• Every place has a different
weather conditions
(e.g : rainy day, sunny day)
• Involves large area
• Long Period
• Doesn’t change – fixed/suits
every
Area
• Same climate within each area
(e.g. :Tropical, Mediterranean)

6. Climate is the average weather in a place over many
years.
While the weather can change in just a few hours, climate
takes hundreds, thousands, even millions of years to
change.

8. Climate at any point on earth is determined by:
1. Movement of the atmosphere
2. The proximity of the oceans, and
3. Latitude and altitude of the location
Climate is also affected by:
1. The Sun,
2. Changes in the earth’s orbit
3. Human activities, particularly the burning of fossil
fuels, which may lead to a Greenhouse effect.
4. Seasons happen because of earth’s tilt. (more solar
radiations are received by earth in northern hemisphere.)

9. GLOBAL CLIMATIC FACTORS
• Quality of Solar Radiation
• Quantity of Solar Radiation
• Tilt of the Earth’s Axis
• Radiation of the Earth Surface

10. 1. Quality of Solar Radiation
• The earth receives almost all its energy from
the sun in the form of radiations.
• Thus, the SUN is the dominating influence
on climate.
• Some of the shorter wave length are
absorbed by the atmosphere and radiated at
much longer wave length

11. ……..Quality of Solar Radiation – contd.
According to human means of perception,
we can distinguish :
a. ultra-violet radiation, 290 – 380 nm (producing
photo-chemical effects, bleaching, sunburn, etc)
b. visible light, 380 (violet) – 700 (red) nm
c. short infra-red radiation, 700 – 2300 nm,
(radiant heat with some photo-chemical effects)

12. 2. Quantity of Solar Radiation
• The intensity of radiation reaching the upper
surface of the atmosphere is taken as the
solar constant
• The earth moves around the sun in a slightly
elliptical orbit.

13. ……..Quantity of Solar Radiation – contd.

14. 3. Tilt of Earth’s Axis
• The Earth spins slowly around its own axis, and makes a full
turn with respect to the Sun. This is called Rotation and
Revolution.
• The earth rotates around its own axis (Rotational Axis)
• Each complete rotation making a day = 24hour/day (1000
miles/hour)
• Due to the tilted position, however, the area receiving the
maximum intensity moves north and south between the
tropic of Cancer (latitude 23.5ºN) and the tropic of Capricorn
(latitude 23.5ºS).
• This is the main cause of seasonal changes.

15. Earth’s Rotation
The direction of rotation of the Earth can be
thought of as
– Counter clockwise at the north pole
– From left to right (eastward) at the
equator.
– Parallels of latitude divide the globe
crosswise into rings.
– Meridians of longitude divide the globe
from pole to pole.

16. A solstice is an astronomical event that happens twice
each year when the Sun's apparent position in the sky,
as viewed from Earth, reaches its northernmost or
southernmost extremes.

17. Same amount of sunlight
hitting different latitudes of
Earth’s surface.
Further away from the
equator, at high latitudes,
energy from the sun has to
pass through more
atmosphere, and is spread
out over a larger area on the
surface, Closer to the equator
and at low latitudes, energy
from the sun has to pass
through less atmosphere.

18. Axis Of Earth Affecting Climate
On the day of an equinox, daytime and nighttime are of approximately equal duration
all over the planet.
A solstice is an event occurring when the Sun appears to reach its most northerly or
southerly excursion relative to the celestial equator on the celestial sphere.

19. Summer happens in the hemisphere tilted towards the
Sun, and winter happens in the hemisphere tilted away
from the Sun.

20. Sun Path
Sun path diagrams are
representations of the
Sun's path across the
sky on a flat surface.
They are used to easily
and quickly determine
the location of the sun at
any time of the day and
at any time of the year.

21. To measure the angle of the sun in its motion across the sky, we need to
take its altitude and azimuth reading.
Altitude is the angular distance above the horizon measured
perpendicularly to the horizon. It has a maximum value of 90 deg. at the
zenith, which is the point overhead.
Azimuth the angular distance
measured along the horizon in a
clockwise direction. Azimuth
starts from exactly north, at 0
degrees, and increases
clockwise.
The altitude is symbolized by β
starts from the horizon while the
azimuth is symbolized by α
which starts from the South Pole
and travels clockwise.

22. Radiation at The Earth’s Surface
The earth-sun relationship affects the amount of radiation
received at a particular point on the earth’s surface in three
ways :
1. The cosine law
2. Atmospheric depletion
3. Duration of sunshine

23. Radiation at The Earth’s Surface
1. The cosine law
– which states that the intensity on a tilted surface equals
the normal intensity times the cosine of the angle of
incidence area, therefore less radiation falls on unit area.
Figure shows how the same amount of radiation is
distributed over a larger area, therefore less radiation falls
on unit area.

24. Radiation at The Earth’s Surface
2. Atmospheric Depletion
The absorption of radiation by ozone, vapors and dust
particles in the atmosphere.
The lower the solar altitude angle, the longer the path of
radiation through the atmosphere = smaller part reaches
Earth’s surface.
Also affected by the momentary state of atmosphere i.e.
purity, vapor, dust, smoke etc.
3. Duration of sunshine i.e. the length of daylight period.

25. THE EARTH’S THERMAL BALANCE
The total amount of heat absorbed by earth is each year is
balanced by a corresponding heat loss. This heat releases
by three processes
1. By long wave radiation to cold outer space (84% is
reradiated is absorbed by the atmosphere and 16%
escapes to space)
2. By evaporation : the earth’s surface is cooled, as liquid
water changes into vapor and mixes with air.
3. By convection : air heated by contact with the warm
earth surface becomes lighter and rises to the upper
atmosphere, where it dissipates its heat to space

26. THE EARTH’S THERMAL BALANCE

27. Wind
Winds are basically convection currents in the atmosphere,
tending to even out the differential heating of various
zones.
The pattern of movement is modified by the earth’s
rotation.
At the maximum heating zone (which is somewhere
between the tropics of Cancer and Capricorn) air is heated
by the hot surface, it expands, its pressure is decreased, it
becomes lighter, it rises vertically and flows off at a high
level towards colder regions.

28. When it gets cooled it descends towards sub-tropic
regions, from where the cooler, heavier air is drawn
toward equator from both north and south.
The area where they meet and rises and tropical front is
formed is referred as inter-tropical convergence zone.
This area experiences either completely calm conditions
or only light breezes of irregular directions and is known
as doldrums. This phenomenon of wind affect the global
climate.

30. Effects of Wind
Contrasts in temperature create winds. Hot air rises,
allowing cooler air to flow underneath. This movement of
air from cooler to warmer areas is wind.
Local winds are created by normal fluctuations in
temperature from day to night, but global winds have a
more direct effect on the climate of a region.
Because the sun is more intense at the equator, global
wind patterns called prevailing winds form. Hotter air at the
equator rises and spreads toward the poles.
Prevailing winds either bring moisture to the land or take it
away, depending upon the orientation of the land to the
prevailing wind direction.

31. Effects of Wind
Convective circulation along with the Earth’s rotation establishes
certain patterns within the earth's atmosphere.
Wind – Movement of air within the atmosphere. Air moving parallel to the
ground is called Wind. Air moving up or down is called a Current
Prevailing winds – blow predominantly in one direction throughout the
year.
Trade Winds – Belts of prevailing winds that are found in both
hemispheres between 30° north and south latitudes.
Westerlies – prevailing winds blowing from west between 30° and 60°
north and south latitudes.
Polar Easterlies – prevailing winds blowing from east in the polar
region.

32. Effects of Wind
Atmosphere rotates with earth.
It has tendency to lag behind
the rotation of earth as it is light
in weight and held against
earth due to gravity and
friction. At equator there is a
slippage between earth and
atmosphere cause by what is
known as Coriolis force. This
effect is experienced as a wind
blowing in a direction opposite
to earth’s rotation.
Actual wind is resultant of thermal force and Coriolis force i.e.
northeasterly wind and south-easterly winds.

33. Effects of Wind
In the Northern
Hemisphere, Coriolis effect
causes things to curve Right
In the Southern
Hemisphere, Coriolis effect
causes things to curve Left

34. Local Winds
– These winds blow over small areas
– Unlike planetary winds, local winds can change speed and direction
frequently
– These are the winds we feel on the ground
– They are influenced by local conditions and local temperature
variations
Air movements can be generated on quite a small scale, e.g.
between a lake and its shores, between a quarry and a nearby
forest, between a town and the surrounding countryside or even
between the sunny and shaded sides of a large building.

35. Effects of Topography
Temperature decreases with altitude, so mountainous
regions, plateaus etc can have cooler than expected
temperatures (hence glaciers on Mt Kilimanjaro near the
Equator).
Secondly, the orientation of a slope in higher latitudes can
affect the local climate; south facing slopes in northern extra-
tropical regions (say Canada) will be warmer and get more
hours of sunlight than north facing slopes.
Mountain ranges can act as barriers to wind and rainfall, with
much of the rain falling on the windward side and top of the
mountain and the lee of the mountain in 'rain-shadow‘, i.e. with
little rain.
Mountains can also control local winds.

36. Precipitation
• Precipitation includes water in all its forms rain, snow,
hail or dew
• It is usually measured in millimetres (mm) by using a rain
gauge
• Rains in warm climates tends to make the built
environment and surrounding microclimate cooler .
CLOUD COVER Regulates the amount of solar radiation
reaching the earth’s surface. Thus a cloudy day is cooler
than a day we have a clear sky. Similarly at night when the
earth is in cooling mode it cools off quickly under the clear
sky than a cloudy one.
Measured in % of clear sky