Page 138 - SST Class 07

WEATHER AND CLIMATE between day and night. The
It is the hour-to-hour, day-to-day conditions of
the atmosphere. It changes dramatically from day
to day. Even metaphorically it is said ‘as change-
able as the weather’. Weather may be : hot,
humid, pleasant or breezy.
The first two weather conditions might make us
irritable and make it impossible to go for an
outing with friends. The third and fourth weather
conditions are welcome and acceptable by all.
We get to hear the weather report across the
world on news channels. Weather forecast is also
important for us to plan our day. It is especially
important for fishermen who are warned not to
venture into the sea due to high tide forecast, for
cricket fans and players speculating the outcome
of a One Day match, etc.
The average weather condition of a place for a
longer period is called the climate of that place.
Weather pattern of more than 20 years is consid-
ered for defining the climate of a place.
Meteorology : It is the study of the atmosphere.
An operational forecaster analyses weather
conditions and issues forecasts or alerts the
public of severe weather for their area.
The following are the aspects to be studied while
studying the concept of weather and climate :
g Temperature
g Air Pressure
g Wind
g Moisture
Temperature
Temperature refers to the degrees of hotness or
coldness of the air. The main source of this heat
is the insolation or the amount of solar energy
received by the earth. The amount of heat
depends upon the latitudinal location of any
place. It is higher in places near the equator and
decreases pole-wards. The amount of insolation
received differs from season to season and also
Social Science-7 138
earth has been broadly
divided into three heat zones
depending upon the amount
of insolation received. The
temperature of any place also
depends upon its height above
sea level and its distance from
the sea. Places located near
the sea will experience moder-
ate temperature but those,
away from the sea, will gener-
ally experience extreme Thermometer
temperature.
Of course, the temperature recording is never
solely dependent on any one factor. Various
factors affect the climate of a place. Winds, ocean
current, slope of land, vegetation-cover are the
many factors that influence the temperature
recordings. Temperature is recorded by a ther-
mometer on a Fahrenheit or a Celsius scale.
Air Pressure
The air above us presses us with great force. But,
we do not feel it at all. This is because it presses
us from all directions and our body exerts a
counter pressure. Air pressure is defined as the
pressure exerted by the weight of air on the
earth’s surface.
Nature of Vertical Air Pressure : The pres-
sure falls rapidly as we go up the layers of the
atmosphere. Therefore, the pressure is the
highest at sea level and decreases with altitude.
Nature of Horizontal Air Pressure :
Horizontally, the distribution of air pressure is
influenced by the temperature of the air at a
given place.
Where the temperature is high, the air gets
heated up and rises, thus creating a low-pressure
area. This is associated with cloudy sky and wet
weather.