Climatology - Introduction.pptx

CLIMATOLOGY
UNIT- 1
INTRODUCTION
Presented by
Agilandeeswari. R

• The climate is based on long term trends and is measured over
years whereas weather is short term and changes rapidly.
CLIMATE
It is a measure of Average
Pattern of variation in
temperature, humidity,
atmospheric pressure,
wind, precipitation and
other meteorological
variables in a given
region over a long period
of time.

GLOBAL
CLIMATIC
FACTORS
 Quality of a Solar Radiation
 Quantity of Solar Radiation
 Tilt of the Earth’s Axis
 Radiation of the Earth Surface
 Wind and Air Masses
EaRTH
CLIMATIC
FACTORS

QualityOf Solar
Radiation
The earth’s surface receives most of its energy in short wavelengths.
The energy received by the earth is known as incoming solar radiation
which in short is termed as insolation.
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 Wavelength are absorbed by the atmosphere and
radiated at much longer wavelength.
UltraViolet (290 – 380 nm)
Visible (380 – 700 nm)
Infra-red (700 – 2300 nm)

Earth’s radiation Balance
Three Main Components
of Solar Radiation

• Shortwave and longwave
radiation interacts with the
earth and atmosphere in
different ways.
• Shortwave radiation (visible
light) contains a lot of
energy; longwave radiation
(infrared light) contains less
energy than shortwave
radiation .
• shortwave radiation has a
shorter wavelength than
longwave radiation.

QuantityOf Solar
Radiation
The earth moves around the sun in the Slightly ellipticalOrbit.
The Spectral energy distribution varies with ALTITUDE (Filtering
effect – shorter wavelength absorbed by atmosphere) .
The intensity of Solar Radiation
reaching the Upper surface of
the atmosphere is taken as
solar Constant. SOLAR
CONSTANT: 1395W/m2

Because of the curvature of the Earth, the same amount of sunlight will be spread
out over a larger area at the poles compared to the equator.
The equator therefore receives more intense sunlight, and a greater amount of heat
per unit of area.

FACTORS THAT
DETERMINE THE
CLIMATE OF A
PLACE
 Location
 Temperature
 Precipitation
 Humidity
 Altitude
 Latitude
 Tilt of the Axis
 Surface Currents
 Winds and
 Elevation
 Vegetation
 Latitude
 Topography
 Ocean Currents
 Wind
 Temperature
 Location
 Elevation
 Pressure and prevailing winds

Latitude measures how close a place is to the Equator and is the most important
factor that influences climate.
• The places located at higher altitudes lie far from the equator and receive less
sunlight and places that are situated towards the equator receives more sunlight
and are hotter than the places located at higher latitudes.
• Sunlight also causes low precipitation or rainfall.
Factors that
Influence
Climate
LATITUDE
Altitude, or elevation, measures how high the land is above the sea level.
High altitude means that a place has cooler climate; low altitude means that a place has
warmer climate. Clouds can't hold a lot of water when it's cold, so it's often wetter at
higher altitudes too.
ALTITUDE
• The place at higher region or at high altitude the atmosphere experiences less
pressure. As the gas residing in the atmosphere rises, it experiences feeling less
pressure, hence causing it to expand.
• Latitude,
• Altitude,
• Relief and
• Distance from the sea.

DEFINITIONS Latitude
• The places located at higher altitudes lie far from the equator and
receive less sunlight and places that are situated towards the
equator receives more sunlight and are hotter than the places
located at higher latitudes.
• Sunlight also causes low precipitation or rainfall.
• The place at higher region or at high altitude the atmosphere
experiences less pressure.
• As the gas residing in the atmosphere rises, it experiences feeling
less pressure, hence causing it to expand.
Altitude
Ocean Currents
Ocean currents are able to transfer heat energy from land to sea or
vice versa thus affecting the temperature of the region.

MOVEMENT OF
EARTH AROUND SUN
TILT OF THE EARTH ’ S
AXIS
•The axis of this rotation is tilted to the plane of the elliptical orbit, at an angle of
66.5 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 o f solar radiation.
• Due to the tilted position, however the area receiving the maximum intensity
moves north and south between the tropic of cancer and the tropic Capricorn.
•This is the main cause of seasonal changes.
The axis of the earth which is an imaginary line, makes an angle of 66½° with its
orbital plane.The plane formed by the orbit is known as the orbital plane.The
earth receives light from the sun.

DEC 22 Winter solstice
June 22 Summer solstice
Movement of
Earth
aroundSun
This is the main cause of seasonal changes.

The summer solstice in northern hemisphere brings the longest day of the year and
the shortest night.
Winter Solstice-Shortest day of the year and longest night.
OBLIQUITY
OBLIQUITY –Tilt of the earth’s axis of rotation
Solstice
and
Equinox

The summer solstice is an annual astronomical phenomenon that brings the
longest day of the year and the shortest night.
Summer Solstice

The earth has two types of motions, namely rotation and revolution.
Rotation :The movement of the earth on its axis.
Revolution:The movement of the earth around the sun in a fixed path or orbit
Movement of
Earth
aroundSun TILT OF THE EARTH ’ S AXIS
• The earth rotates around its own axis, each rotation making one 24 hour
day. The axis of this rotation is tilted to the plane of the elliptical orbit, at
an angle of 66.5 and the direction of this axis is constant.
• 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 o f solar radiation.
moves north and south between the tropic o f cancer and the tropic of
Capricorn.
• This is the main cause of seasonal changes.
orbital plane.The plane formed by the orbit is known as the orbital plane.The
earth receives light from the sun.

One complete Rotation equals day and night ( 24 Hrs).
Earth Complete one Revolution in 365 and one quarter day. Leap Year adds a day to
the calendar every 4 years.
Movement of
Earth
aroundSun
The earth has two types of
motions, namely rotation and
revolution.
Rotation : The movement of
the earth on its axis.
Revolution: The movement
of the earth around the sun in
a fixed path or orbit
orbital plane. The plane formed by the orbit is known as the orbital plane or Elliptical
Plane.The earth receives light from the sun.

MOVEMENT OF
EARTH AROUND SUN
TILT OF THE EARTH ’ S
AXIS
As we know, our earth has two types of rotation,
1.Orbital rotation around the sun – It causes years on earth.
2.Axial rotation around its own axis – It causes days on earth.
While orbiting around the sun, it rotates
on its axis. But this rotational axis is tilted
around 23.5°.
the rotational axis is tilted almost 23.5° from
the perpendicular to the orbital axis.
This tilt causes some regions of the earth to
get direct sunlight whereas some regions do
not get enough sunlight. The earth’s parts
(regions) where the sunlight is direct happen
in summer at that time. And the earth
regions which do not receive enough
sunlight have winter seasons.

moves north and south between the tropic of cancer an d the tropic Capricorn.
• This is the main cause of seasonal changes.
MOVEMENT OF
EARTH AROUND SUN
TILT OF THE
EARTH ’ S AXIS

MOVEMENT OF
EARTH AROUND SUN
TILT OF THE
EARTH ’ S AXIS

Summer Solstice Winter Solstice
Summer solstice occurs when North Pole is
tilted closest to the Sun and brings the longest
day in the Northern Atmosphere.
Winter solstice occurs when North Pole is
tilted farthest from the sun and brings the
longest night in the Northern Hemisphere.
It occurs on 21st June It occurs on 22nd December
Southern Hemisphere has the shortest night Southern Hemisphere has the longest days
Sun rays directly fall overTropic of Cancer Sun rays directly fall overTropic of Capricorn
The places beyond the Arctic circle experience
continuous daylight for about six months
The places beyond the Antarctic circle
experience continuous daylight for about six
months
As a large portion of Northern Hemisphere
receives sunlight and heat during summer
solstice, it is summers in Northern
Hemisphere; whereas winters in Southern
Hemisphere
As a large portion of Southern Hemisphere
receives sunlight and heat during winter
solstice, it is summer in Southern Hemisphere,
whereas summers in Northern Hemisphere
Summer solstice
vs
winter solstice

Climateand
Built Form
Interaction

• Temperature
• Pressure
• Winds
• Humidity
• Precipitation
ELEMENTS OF CLIMATE

Elements of
Weather and
Climate

• It is generally expressed in degree Celsius (ºC).
• Temperature at a given site depends on wind as well as local factors
such as shading, presence of water body, sunny condition, etc.
Dry-bulb temperature is the actual temperature of air (value taken in
shade) as measured by an ordinary thermometer.
Wet-bulb temperature is the temperature at which the air would become
saturated if moisture were added to it without the addition or subtraction
of heat.
It is the temperature of a air recorded by a thermometer, when its bulb is
surrounded by a wet cloth exposed to the air, such a thermometer is called
wet bulb thermometer.
ELEMENTS OF CLIMATE
TEMPERATURE
The temperature of air in a shaded
(but well ventilated) enclosure is
known as the AMBIENT
TEMPERATURE

• Amount of water vapor
(moisture) content present in
the air.
• The more water vapour in the
air the higher the humidity.
• High humidity accompanied
by high ambient temperature
causes a lot of discomfort.
Absolute Humidity - the amount of moisture
actually present in unit mass or unit volume of air,
in terms of gramme per kilogramme (g/kg) or
gramme per cubic metre (g/m3 ).
The relative humidity (RH) - Relative humidity is
the ratio of the actual amount of moisture
present, to the amount of moisture the air could
hold at the given temperature – expressed as a
percentage.
RH = (AH/SH ) X 100
Humidity is usually measured with the wet-and-dry-bulb hygrometer.
*The amount of moisture the air can hold (the saturation point humidity: SH)
depends on its temperature.
• Humidity varies with temperature and is
measured in Percentage.
ELEMENTS OF CLIMATE
HUMIDITY

• Precipitation is defined as water reaching Earth’s surface by falling either in a
liquid or a solid state.
• The most significant forms are rain and snow, , hail or dew.
• Precipitation is expressed in millimetres by Using Rain Gauge.
ELEMENTS OF CLIMATE
PRECIPITATION

• Wind velocity is measured by propeller ANEMOMETER.
• The unit is m/s. It is a major design consideration for architects because it affects
indoor comfort conditions by influencing the convective heat exchanges of a
building envelope, as well as causing air infiltration into the building
• Wind is the climatic element
that transports heat and moisture
into a region and causes
variations in climate by drying
humidity, causing storms, and
contributing to water
evaporation.
• wind - direction, speed, and
gustiness.
• Wind is therefore usually
discussed in terms of prevailing
direction, average speeds, and
maximum gusts.
ELEMENTS OF CLIMATE
WIND
Wind is the movement of air due to
a difference in atmospheric
pressure, caused by differential
heating of land and water mass on
the earth’s surface by solar
radiation and rotation of earth.

• Air pressure is maximum
at sea level.
• Air pressure is measured
in terms of height of
mercury in the glass tube.
• Barometers are used to
measure atmospheric
pressure
ELEMENTS OF CLIMATE
ATMOSPHERIC
PRESSURE
The air present in the
atmosphere has its own weight
and it exerts pressure on the
Surface on the earth. Thus the
pressure exerted by the
atmosphere is called
Atmospheric Pressure.

Ecology is the science of the study of ecosystems.
Ecological Balance is "a state of dynamic equilibrium within a community of organisms
in which genetic, species and ecosystem diversity remain relatively stable, subject to
gradual changes through natural succession." and "A stable balance in the
numbers of each species in an ecosystem."
ECOLOGICAL
BALANCE
Ecological climatology is an interdisciplinary framework to understand the
functioning of terrestrial ecosystems in the Earth system. It examines the physical,
chemical, and biological processes by which ecosystems affect and are affected by
climate.The central theme is that terrestrial ecosystems, through their cycling of
energy, water, chemical elements, and trace gases, are important determinants of
climate.

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