The document provides an overview of climatology and global climatic factors. It discusses five main climate types - tropical, dry, temperate, continental, and polar. Key global climatic factors that influence climate are also summarized, including solar radiation quality and quantity, the tilt of the Earth's axis, radiation at the Earth's surface, the Earth's thermal balance, winds driven by thermal forces like trade winds and the coriolis effect, mid-latitude westerlies, polar winds, annual wind shifts, and the influence of topography. Climate is defined as averaged weather over 30 years, while weather reflects short-term atmospheric conditions.

1. Climatology
Arch 302
Submitted by –
Lipika Pandey
Roll – 27802319002
Sem – 3
B.Arch, RRSA

2. Outline
• Introduction to Climate
• Global Climatic Factors
– Climate and Tropical Climate
– Solar Radiation: Quality
– Solar Radiation: Quantity
– Tilt of the Earth’s axis
– Radiation at the Earth’s surface
– The Earth’s Thermal Balance
– Winds: Thermal balance
– Trade winds: the Coriolis Force
– Mid Latitude westerlies
– Polar Winds
– Annual wind shifts
– Influence of Topography

3. Introduction to Climate
• Climate is commonly defined as the weather
averaged over a long period (generally over a period
of 30 yrs).
• Weather reflects short-term or momentary
conditions of the atmosphere environment while
climate is the average daily weather for an
extended period of time at a certain location.
• Climate is an important part, to be considered
while construction, as due to global warming,
disasters may occur.
• Basic zones of climate are –
– Hot and Arid (Deserts)
– Warm and Humid (Tropical areas)
– Cold and Dry (Poles)

4. Introduction to Climate
• Climate scientists split the Earth into approximately five
main types of climates. They are:
A: Tropical. In this hot and humid zone, the average
temperatures are greater than 64°F (18°C) year-round and
there is more than 59 inches of precipitation each year.
B: Dry. These climate zones are so dry because moisture is
rapidly evaporated from the air and there is very little
precipitation.
C: Temperate. In this zone, there are typically warm and humid
summers with thunderstorms and mild winters.
D. Continental. These regions have warm to cool summers and
very cold winters. In the winter, this zone can experience
snowstorms, strong winds, and very cold temperatures—
sometimes falling below -22°F (-30°C)!
E: Polar. In the polar climate zones, it’s extremely cold. Even in
summer, the temperatures here never go higher than 50°F
(10°C)

5. Global Climatic Factors
• Climate and Tropical Climates
– Climate (from Greek: klima) is defined by
Oxford dictionary as ‘region with conditions
of temperature, dryness, wind, light, etc’. It
could also be defined as the ‘integration in
time of weather conditions’.
– Tropical climates are those where heat is the
dominant problem, for the greater part of
the year buildings serve to keep the occupants
cool, rather than warm, where the annual
mean temperature is not less than 20C.

6. Global Climatic Factors
• Solar Radiations: Quality
– The Earth receives almost all its energy from the sun in the
form of radiations, thus the sun is the dominating influence
on climates
– The spectrum of solar radiation extends from 290-2300nm.
– Ultra-Violet radiations – 290-380nm – produces photo-
chemical effects, bleaching, sunburn, etc.
– Visible Light radiations – 380 (violet)-700 (red) nm
– Short infra-red radiations – 700-2300nm – radiant heat
with some photochemical effects.
– Due to the filtering effect of the atmosphere, the spectral
energy distributions varies with altitude.
– There is no constant relation between radiation intensity and
its lightening effect, as the luminous efficiency of energy-
radiation depends on its spectral composition.
– As a general value, 100 lumens/watt is used for solar
radiations.

7. Global Climatic Factors
• Solar Radiations: Quantity
– The intensity of radiation reaching the upper surface of
the atmosphere is taken as the solar constant:
1395W/m², but it may actually vary  2% due to
variation in the output of the sun itself and it varies 
3.5% due to its change in the Earth-Sun distance.
– The Earth moves around the sun in slightly elliptical
orbit.
– One revolution is completed in 365days 5hours
48minutes 46seconds.
– This orbit results from the gravitational pull of the sun
and the centrifugal force due the Earth’s inertia and
momentum.
– At aphelion the solar distance is 152million km and at
perihelion is 147million km.

8. Global Climatic Factors
• Tilt of Earth’s Axis
– The Earth rotates around it’s own axis,
each rotation making one 24hours day.
– The axis of this rotation(the line joining the
North-South poles) is tilted to the plane of
the elliptical orbit, at an angle of 66.5(i.e.,
a tilt of 23.5 from the North) and the
direction of this axis is constant.
– Maximum intensity is received on a plane
normal to the direction of radiation.
– If the axis of Earth were rectangular to the
plane of the orbit, it would always be the
equatorial regions which are normal to the
direction of solar radiation.

9. Global Climatic Factors
• Tilt of Earth’s Axis
– Due to the tilted position, the area receiving the
maximum intensity moves North and South,
between the Tropic of Cancer(latitude 23.5N) and
the Tropic of Capricorn(latitude 23.5S). This is the
main cause of Seasonal Changes.
– On 21st June, Tropic of Cancer receives maximum
Sun rays, hence experiencing the longest daylight
period, whereas, the Tropic of Capricorn receives
minimum Sun rays, hence experiencing the shortest
day.
– On 21st March and 23rd September, areas along
the Equator are normal to the Sun’s ray, hence for
all areas of the Earth days are the Equinox days
(day and night of equal length).

10. Global Climatic Factors
• 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:
– The Cosine Law – states that the intensity on a tilted
surface equals the normal intensity times the cosine of
the angle of incidence. That is, the same amount of
solar radiations can be distributed over a larger area.
– The Atmospheric Depletion – is the absorption of
radiations by ozone, vapours and dust particles in
atmosphere. The lower the solar altitude angle, the
longer the path of radiation through the atmosphere,
thus a small part reaches the Earth’s surface.
– The Duration of Sunshine – is the length of the
daylight period.

11. • The Earth’s Thermal Balance
– The total amount of heat absorbed by the Earth each year is
balanced by a corresponding heat loss.
– Without this cooling, the thermal balance of the Earth could
not be maintained, the temperature of the Earth and its
atmosphere would increase and would soon cease to be
favourable to most forms of life.
– The Earth’s surface releases heat by three processes –
– By Long wave radiation to cold outer space (some 84% of
this reradiation is absorbed in the atmosphere, and only
16% escapes to the space)
– By Evaporation, the Earth’s surface is cooled, as liquid
water changes into vapour and mixes with air.
– 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.
Global Climatic Factors

12. Global Climatic Factors
• Winds: Thermal Forces
– Winds are basically the convection
currents in the atmosphere, tending
to even out the differential heating
of various zones.
– The pattern movement is modified
by the Earth’s rotation.
– At maximum heating zone, air is
heated by the hot surface, it
expands, it’s pressure is decreased, it
becomes light, so it rises vertically
and flows off at a higher level
towards colder regions.

13. Global Climatic Factors
• Winds: Thermal Forces
– Part of this air having cooled down at the
higher lever, descends to the surface of the
subtropic regions, from where the cooler,
heavier air is drawn in towards the Equator
from both North and South.
– The area where the air rises, where these
Northerly and Southerly winds meet, where
the Tropical Front is formed, is referred to
as the Inter-Tropical Convergence Zone
(ITCZ).
– This area experiences either completely calm
conditions or only very light breezes of
irregular directions and is referred as
‘doldrums’.

14. Global Climatic Factors
• Trade Winds: the Coriolis Force
– The atmosphere rotates with the Earth. As it is
light in weight and behaves as fluid, held against
the Earth’s surface only by gravity and friction, it
has a tendency to lag behind the Earth’s rate of
rotation where this rotation is the fastest, i.e, at
the Equator.
– There is a slippage at the boundary layer between
the Earth and its atmosphere caused by what is
known as the ‘Coriolis Force’.
– The effect is experienced as a wind blowing in the
direction opposite to that of the Earth’s rotation.
– The actual wind is the resultant of thermal and
coriolis forces- the north-easterly winds north of
the Equator and south-easterly winds south of the
Equator. These are known as North-East and
South-East trade winds.

15. Global Climatic Factors
• Mid Latitude Westerlies
– Around 30 N and S, there are two bands of
continually high barometric pressure (descending air).
– Winds in these zones are typically light and variable.
Between 30 and 60 N and S, however strong
westerly winds prevail, blowing in the same direction
as the Earth’s rotation.
– It can be explained by the law of Conservation of
Angular Momentum.
– The total angular momentum of the Earth-
Atmosphere system must remain constant.
– If it is reduced at the Equator by easterly winds, this
must be compensated for by westerly winds
elsewhere.

16. Global Climatic Factors
• Polar Winds
– Towards the poles from latitudes 60N and S, the air flow
pattern comes under the influence of thermal factors.
– The pattern is similar to that near the Equator.
– Air at the surface moves from the coldest to the slightly
warmer regions (away from poles).
– As the circumferential velocity of air at the at the poles is
almost nil, the air will lag behind the rotating Earth as it
moves away from the poles.
– The northerly is deflected into north-easterly and the
southerly into the south-easterly polar winds.
– At the meeting point of cold polar winds and the mid-
latitude westerlies, a band of low pressure – a sub polar
front –is formed, with highly variable and strong winds.

17. Global Climatic Factors
• Annual Wind Shifts
– During the course of each year the global wind
patterns shifts from north to south and back again,
remaining broadly symmetrical about the ITCZ.
– The location of the ITCZ follows the maximum solar
heating, i.e., the zenith path of the sun, with a delay
of about a month.
– The extreme north and south positions of the ITCZ
are in July (north) and in January (south).
– As a consequence of this annual shift most regions of
the Earth experiences seasonal changes not only in
temperature but also in wind directions and in
rainfall.

18. Global Climatic Factors
• Influence of Topography
– On a continental scale, wind and weather are the
results of an interaction between broad global flow
patterns and regional pressure and temperature
patterns created by the sun’s differential heating
effect on land, forest and water.
– The force, direction and moisture content of air
flows are strongly influenced by topography.
– Air can be diverted or funneled by mountain
ranges. Air flow detected upwards, as it cools,
releases its moisture content. A descending air
mass will very rarely give any precipitation,
therefore rainfall characteristics vary sharply
between locations on windward and leeward
slopes of the mountain ranges.

19. Global Climatic Factors
• Influence of Topography
– The humidity of air will vary with the rate of
evaporation of moisture from the surface
below, i.e., it depends on the availability of
water to be evaporated.
– Air movement can be generated on quite a
small scale, e.g., between a lake and its shores,
between a town and surrounding countryside,
even between a sunny and shaded sides of a
large building.

20. THANK YOU