What is weather and climate and how are they interrelated?

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Temperature, pressure, wind, humidity, and precipitation, interact with each other. They influence the atmospheric conditions like the direction and velocity of wind, amount of insolation, cloud cover, and the amount of precipitation.
1. MODULE - 4 Weather and Climate
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the Earth
In the preceding three lessons, we have discussed about the temperature,
atmospheric pressure, winds and precipitation. These elements of weather
have an important effect on our lives. For example the houses we construct,
the clothes we wear and the food we prefer mainly depend on weather and
climatic conditions. In this lesson, we will study about the difference among
weather, season and climate and also the factors affecting climate of a place.
After studying this lesson you will be able to:
 name the various elements of weather and climate;
 differentiate among weather, season and climate;
 explain the need for forecasting weather in advance;
 explain with specific example the various factors affecting the climate
of a place or region;
 describe the important characteristics of each thermal zone with the
help of a diagram;
 state Koeppen’s classification of climate.
(i) Weather
Temperature, pressure, wind, humidity and precipitation, interact with
each other. They influence the atmospheric conditions like the direction
and velocity of wind, amount of insolation, cloud-cover and the amount
of precipitation. These are known as the elements of both weather and
climate. The influence of these elements differs from place to place
2. Weather and Climate MODULE - 4
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and time to time. It may be restricted to a small area and for a short the Earth
duration of time. We very often describe this influence in the name of
weather as sunny, hot, warm, cold, fine, etc depending upon the
dominant element of weather at a place and at a point of time. Therefore,
weather is the atmospheric condition of a place for a short duration
with respect to its one or more elements. Two places even a short Notes
distance apart may have different kind of weather at one and the same
(ii) Weather Forecast
It is important to know by some means the coming weather in advance.
You may be planning to go on a hike without knowing that the particular
day may be rainy. Farmers, sailors, aviators, tourists and many others
are interested to know the weather conditions in advance for their own
benefits. That is why newspapers publish weather reports and weather
forecasts along with a map showing this information. Now, better
weather forecasts are available with the use of weather satellites.
Weather conditions are televised every day. When a cyclone or
dangerous weather is expected, warnings are issued over the radio,
television and newspapers so that people can prepare to save themselves
and their property from its hazard.
The weather office collects data on temperature, wind, cloud cover,
rainfall and other atmospheric phenomena through its numerous
observation centres. These centres are scattered all over the country.
Similar information is also received from the ships sailing in the high
seas. The analysis of these data thus collected, helps in forecasting
weather conditions for the next 48 hours or even for a week. The
significance of a weather information supplied through a map and its
forecast is better utilised in a country like the U.K. where weather
changes are very rapid.
(iii) Season
You know that a year is divided into seasons depending upon variations
in atmosphric conditions. They are specified periods in a year which
have similar weather conditions. Season is a period of the year
charcterized by a particular set of weather conditions resulting from
the inclination of the earth’s axis and the revolution of the earth round
the sun. The same cycle of season is repeated year after year. Four
seasons, each of three months duration have been recognized in
temperate regions. They are spring, summer, autumn and winter. In
our country, we have three distinct seasons which are summer, winter
and rainy. The Indian Meteorological Department has recognized four
main seasons. They are (1) cold weather season (December to
February.) (2) hot weather seasons (March to May) (3) advancing
3. MODULE - 4 Weather and Climate
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the Earth monsoon season or rainy season (June to September.) and. (4) retreating
monsoon season (October to November.)
Traditionally there are six seasons in north India. They are (1) Basant
Ritu (Chaitra- Vaisakh or March-April), (2) Greeshm Ritu (Jaystha-
Asharh or May-June), (3) Varsha Ritu (Shravan-Bhadrapad or July-
Aug.), (4) Sharad Ritu (Aswina-Kartika or Sept - Oct.), (5) Hemant
Ritu (Margashirsh-Posh or Nov-Dec.) and (6) Shishir Ritu (Magh-
Falgun or Jan-Feb.)
The rays of the sun are more or less direct on the equator throughout
the year. Hence, equatorial regions experience the same temperature
all the year round. Therefore, seasons are insignificant on or near the
equator. Near the coast, the oceanic influence reduces the seasonal
variations. In the polar regions, there are only two seasons i.e. long
winter and short summer.
(iv) Climate
The average weather conditions, prevalent from one season to another
in the course of a year, over a large area is known as climate. The
average of these weather conditions is calculated from the data collected
for several year (about 35 years) for a larger area. Rajasthan, for
example, experiences hot and arid climate, Kerala has tropical rainy
climate, Greenland has cold desert climate and the climate of Central
Asia is temperate continental. Climate of a region is considered more
or less permanent.
 Weather is the atmospheric condition of any place for a short period
of time with respect to its one or more elements such as temperature,
pressure, wind, humidity, precipitation, sunshine, cloud cover etc.
 The periods of the year which are characterised by particular set of
weather conditions are mainly caused by the inclination of the earth’s
axis and the revolution of the earth around the sun, are known as
 The average weather conditions of a large area for the past several
years is known as its climate persisting more or less permanent.
The difference between weather and climate can be tabulated as under
Weather Climate
(1) Weather is the study of atmospheric (1) Climate is the study of the
conditions for short duration of a average weather conditions
limited area. observed over a long period
of time for a larger area.
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(2) Weather is influenced by anyone of its (2) Climate is the collective the Earth
predominant element s i.e., effect of all its elements.
temperature or humidity.
(3) The weather changes very often (3) It is more or less permanent.
(4) It is experienced over small areas of a (4) It is experienced over large Notes
country. area of the continent.
(5) A place can experience different types (5) A place can experience only
of weather conditions in a year. one type of climate.
Fill in the blanks by the most appropriate word from those given within
brackets against each of the following:
1. Weather depends upon predominance of____________ of its elements
{(a) one, (b) two, (c) three (d) one or more}
2. The season is___________in equatorial region {(a) predominants, (b)
good, (c) insignificant, (d) always changing.}
3. The average weather conditions for_________duration represent
climate. {(a) one year, (b) long, (c) short, (d) many years.}
4. The exposed skin of our body starts cracking in winter season mainly
due to__________{(a) rainy season, (b) high humidity, (c) summer
season, (d) low humidity}
5. Seasons are caused by_____________{(a) ocean currents and
revolution, (b) air masses and rotation of the earth (c) ocean current
and rotation of the earth, (d) inclination of the earth’s axis and earth’s
6. Four seasons each o f three mont hs durat ion are noticed
in___________zone/region {(a) Temperate, (b) Tropical, (c) Equatorial,
(d) Frigid.}
Different regions of the world have differences in temperature, humidity
and precipitation. You know that these differences influence the lifestyle of
the people living under different climatic conditions. To understand different
climatic conditions, let us discuss the factors which cause the variations in
the climate of a place or a region.
5. MODULE - 4 Weather and Climate
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the Earth 1. Latitude or Distance from the Equator
The places near the equator are warmer than the places which are far away
from it. This is because the rays of the sun fall vertical on the equator and
slanting in the temperate and polar regions. As we have discussed earlier
the vertical rays are concentrated over a small area than the slanting one.
Notes Again, the vertical rays pass through a shorter distance in the atmosphere
before reaching the earth’s surface. Therefore, lower the latitude higher is
the temperature and vice versa. Malaysia which is near the equator is warmer
than England which is far way from the equator.
2. Altitude or the Height from the mean sea level
We all know that mountains are cooler than the plains. Shimla situated on a
higher altitude is cooler than Jalandhar, although both are almost on the
same latitude. The temperature decreases with the height of a place. For a
vertical rise of 165 metres there is an average decrease in temperature at
the rate of 1°C. Thus the temperature decreases with increase in height.
3. Continentally or the Distance from the Sea
The water is a bad conductor of heat i.e. it takes longer time to heat and
longer time to cool. Due to this moderating effect of the sea, places near the
coast have low range of temperature and high humidity. The places in the
interior of the continent do not experience moderating effect of the sea.
These places have extreme temperatures. The places far from the sea have
higher range of diurnal (daily) and annual temperatures. Mumbai has relatively
lower temperature and higher rainfall than Nagpur, although both are almost
situated on the same latitude.
4. Nature of the Prevailing Winds
The on-shore winds bring the moisture from the sea and cause rainfall on
the area through which they pass. The off-shore winds coming from the
land are dry and help in evaporation. In India, the on-shore summer monsoon
winds bring rains while off-shore winter monsoon winds are generally dry.
5. Cloud Cover
In areas generally of cloudless sky as in deserts, temperature even under
shade are very high because of the hot day time sunshine. At night this
heat radiates back from the ground very rapidly. It results in a large
diurnal range in temperature. On the other hand under cloudy sky and
heavy rainfall at Thiruvananthapuram the range of temperature is very
6. Ocean Currents
Ocean waters move from one place to another partly as an attempt to
equalize temperature and density of water. Ocean currents are large
movements of water usually from a place of warm temperature to one of
cooler temperature or vice-versa. The warm ocean currents raise the
temperature of the coast and sometimes bring rainfall, while the cold currents
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lower the temperature and create fog near the coast. Port Bergen in Norway the Earth
is free from ice even in winter due to warm North Atlantic Drift while Port
Quebec in Canada remains frozen during winter months due to chilling effect
of the Cold Labrador Current in spite of the fact that Port Quebec is situated
in much lower latitude than Port Bergen. The on-shore winds passing over
a warm current carry warm air to the interior and raise the temperature of Notes
the inland areas. Similarly, the winds blowing over cold current carry cold
air to the interior and create fog and mist.
7. Direction of Mountain Chains
The mountain chains act as natural barrier for the wind. The on-shore moisture
laden winds are forced to rise after striking against the mountain; and give
heavy rainfall on the windward side. These winds descending on the leeward
side cause very low rainfall. The great Himalayas check the moisture laden
monsoon winds from crossing over to Tibet. This mountain chain also checks
biting polar cold winds from entering into India. This is the reason for which
northern plains of India get rains while Tibet remains a perpetual rain shadow
area with lesser amount of rainfall.
8. Slope and the Aspect
The concentration of heat being more on the gentler slope raises the
temperature of air above them. Its lesser concentration along steeper
slopes lowers the temperature. At the same time, mountain slopes facing
the sun are warmer than the slopes which are away from the sun’s
rays. The southern slopes of Himalaya are warmer than the northern
9. The Nature of the Soil and Vegetation Cover
The nature of soil depends upon its texture, structure and composition.
These, qualities vary from soil to soil. Stony or sandy soils are good
conductor of heat while black clay soils absorb the heat of the sun’s
rays quickly. The bare surface reradiates the heat easily. The deserts
are hot in the day and cold in the night. The forest areas have lower
range of temperature throughout the year in contrast to non-forested
 The factors which affect the climate of a place or region are latitude
or the distance from the equator, altitude or the height from the mean
sea level, continentality or the distance from the sea, nature of the
prevailing winds, ocean currents, direction of mountain chain, slope
and its aspect, nature of soil and the vegetation cover.
Some of the following statements are false and some are true. Write true against
7. MODULE - 4 Weather and Climate
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correct statements and false against wrong ones.
1. Higher the latitude lower is the temperature.
2. Higher the altitude lower is the temperature.
3. Nearer the sea coast lower is the range of temperature.
4. Interiors of the continent have lower range of temperature.
5. Cold ocean currents lower the temperature of the coast.
The varied effect of the major weather elements in different parts of the world and
also the varied nature of the earth’s surface give every location a distinct climate.
Hence, the number of different climate is large. In order to easily understand and
comprehend this large variety, the climate of the world have been classified into a
few major groups, each having certain common important characteristics.
Although several attempts have been made by scholars to classify the climate of
the world for the proper understanding of major climate types no single classification
is perfect, as climate stands for the generalized and composite weather conditions.
However, the Greeks, perhaps, made the first attempt to classify the world climates
on the basis of the distribution of temperature and insolation. They divided the
world into five latitudinal thermal zones, The boundary of these zones are fixed on
the basis of the angle at which the sun’s rays strike the earth. The following are the
five thermal zones.
Fig. 13.1 Thermal Zone
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(a) The Thermal Zones the Earth
(i) Torrid Zone: It is the largest of the thermal zones. It covers, almost half the
area of the earth’s surface. It is situated between the Tropic of Cancer
(23½°N) and Tropic of Capricorn (23½0 South) (See fig 13.1). The sun’s
rays are almost vertical throughout the year in this zone. The mid-day sun is
overhead at equator on equinoxes, i.e. on 21 st March and 23rd September.
It is also overhead at Tropic of Cancer on 21st June and at Tropic of
Capricorn on 22nd December. The duration’s of day and night are always
equal i.e. 12 hours each on the equator and they increase to 13 hours 27
minutes at tropics. The range of temperature is lowest at the equator and it
increases towards the tropics.
(ii) Temperate Zone: The temperate zones are on either side of the Torrid
zone. The North Temperate Zone lies between Tropic of Cancer (23½0
North) and Arctic Circle (66½o North) The South Temperate Zone lies
between Tropic of Capricorn (23½° South) and Antarctic Circle (66½°
South) (see fig. 13.1). The sun is never overhead In this zone in winter
season, the nights are longer and days are shorter and vice versa in
summer. The difference between the duration of the day and night
increases towards the poles. The maximum duration of day in summer
and that of night in winter in the polar circles is 24 hours. When it is
summer in the northern hemisphere it is winter in the southern
hemisphere and vice versa,
(iii) Frigid Zones: Like the temperate zone, frigid zone is also found in
both the hemispheres. The North Frigid Zone lies between Arctic Circle
(66½0N) and North Pole (90° North). The South Frigid Zone lies
between Antarctic Circle (66½0 South) and South Pole (900 South).
During winter season, the sun does not rise above the horizon for almost
six months. These are the coldest regions of the world. The surface
remains permanently frozen under thick snow.
 The earth is divided into five thermal zones on the basis of distribution
of insolation and temperature.
 Five thermal zones are torrid zone, north and south temperate zones
and north and south frigid zones.
1. Fill in the blanks with suitable answers:
(i) The concept of thermal zones was first given by ______________
(ii) The____________passes through the middle of the torrid zone.
9. MODULE - 4 Weather and Climate
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the Earth (iii) Days and nights are always equal at the_____________
(iv) The sun is overhead twice at_______________on 21st March
and 23rd September.
(v) The sun is overhead throughout the year in__________zone.
(vi) The ____________ Zone lies between 23½0 South and 66½°
(vii) The North Frigid Zone lies between 66½0 North and __________
(viii) The perpetual thick snow covers the______________zone.
(b) Climatic Types
The concept of thermal zone is theoretical and explains the distribution of
solar energy over the earth’s surface. As discussed earlier, there are several
other factors besides the angle of the sun’s rays which influence the climate
of a place. Keeping in view other factors responsible for the distribution and
combined influence of temperature and rainfall, modem scientists have arrived
to several classifications of climate and its types. The most widely used system
of climatic classification in its various modified forms is that of Wladimir
koeppen (1846-1940). It is based upon temperature, precipitation and their
seasonal characteristics. The relationship of climate with the vegetation is
also included with it. According to this scheme, the world has been divided
into five climatic groups and they are further sub-divided into 13 climatic
types. They are as follows:
I Climatic Groups Climatic Types
(A) Tropical climates (hot all Af (i) Tropical rain forest
Aw (ii) Savanna Climate
Am (iii) Monsoon Climate
(B) Dry climates Bw (iv) Desert Climate
Bs (v) Steppe Climate
(C) Warm temperate rainy or Cs (vi) Mediterranean Climate
Middle latitude rainy Cw (vii) China Type Climate
climates (mild winters) Cf (viii)West European Climate
(D) Humid Middle latitude Dw (ix) Taiga Climate
climates (severe winters) Df (x) Cool East-coast Climate
(xi) The Continental Climate
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7 (E) Polar climates Et (xii) Tundra Climate the Earth
Ef (xiii) Ice-cap Climate
You will study the specific characteristics of some of these climatic types in
the subsequent lesson dealing with the life of people in low latitude, mid-
latitude and high latitude regions of the world. Notes
 W.Koeppens scheme of climatic classification is based on temperature
precipitation and their seasonal characteristics
 According to this scheme the world has been divided into 5 climatic
groups and 13 climatic types.
1. Match correctly each item of column A with that of column B
A Climate Group B Climatic Types
(a) Tropical Climate (1) Tundra Climate
(b) Dry Climate (2) Taiga Climate
(c) Warm Temperate Climate (3) Savanna Climate
(d) Humid Middle Latitude (4) Steppe Climate
Climates (severs winters)
(e) Polar Climates (5) Mediterranean Climate
The difference among weather, season and climate is that of duration, extent
and permanency. Weather is the atmospheric condition of a place for a short
period of time with respect to one or more of its elements. It is not permanent.
Season is the period of a year which is characterized by a particular set of
weather condition. It is mainly caused by the inclination of the earth’s axis
and revolution of the earth round the sun. Its cycle is repeated year after
year. Climate is the average weather conditions of a large area for the past
several years. It is more or less permanent. Climate of any place or region is
affected by several factors, such as distance from the equator, ocean currents,
direction of mountains. slope and aspect, soil and vegetation cover etc.
Ancient Greeks divided the world into torrid, temperate and frigid zones
based upon the distribution of temperature. Torrid zone is the hottest. the
frigid zone is the coldest and the temperature zone lies in between the two. It
11. MODULE - 4 Weather and Climate
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the Earth has a mild temperature. The length of the day varies from equator to poles. The
days and the nights are almost equal on the equator. The length of the day increases
in summer and decreases in winter as we move towards the poles.
Climate types are the outcome of the classification based upon regions of their
formation. W. Koeppen classified the world into five climatic groups, namely (A)
Tropical Climate, (B) Dry Climate, (C) Humid Mid-latitudes Climate (mid winters),
(D) Humid Mid-Latitudes Climate (severe winters) and (E) Polar Climate. His
classification is based on temperature, precipitation and their seasonal variation.
He sub-divided the climatic groups into 13 climatic types.
1. Explain the factors which affect climate of a place.
2. Draw a simplified diagram of thermal zones and write important
characteristics of each zone.
3. Distinguish between weather and climate by describing five points of
distinction of each.
4. Name the three main basis of Koeppen’s classification of climate and
also state the five climatic groups and their sub-divisions into climatic
1. (d); 2. (c); 3. (d); 4. (d); 5. (d); 6. (a)
1. True;. 2. True; True; 4. False; 5. True
(i) Greeks; (ii) equator; (iii) equator; (iv) equator; (v) Torrid; (vi) South Temperate;
(vii) 90° N or North Pole; (viii) Frigid
(a). (3); (b) . (4) ; (c) . (5) ; (d) . (2) ; (c) . (1)
1. Please see para 13.2
2. Please see para 13.3 (a)
3. Please see para 13.1 (iv)
4. Please see para 13.3 (b)