Unlike climate, weather depends on the seasons and can also change anytime. Meteorologists predict in
the evening how the weather will be the next day. The weather is driven by the sun, which heats up the ground
and the water surfaces. Evaporated water creates clouds from which thunderstorms build up, and the ensuing
bursts of thunder and lightning make us flinch. Every time a cyclone hits the tropical regions, lashing rain sends
people running for cover.
How is the weather predicted?
The weather is predicted by meteorologists-scientists who monitor weather conditions. They study the factors that lead to weather
phenomena in different parts of the world. They observe and record atmospheric temperature,
humidity, pressure, and precipitation and the direction and strength of winds. Weather balloons
and weather stations give out information regarding the state of the atmosphere. On the basis of their findings, they make
forecasts about future weather conditions.
How do tropical cyclones occur?
When we talk about cyclones, we do not usually mean the small destructive tornadoes, but instead the large tropical storms,
which the coastal inhabitants face. In America, these are known as ‘hurricanes’, in East Asia ‘typhoons’, and in India ‘cyclones’.
Hurricanes occur in early spring in the warm waters around Africa. During this season, copious amounts of water evaporate,
rise upwards, and forms clouds. This sharply reduces the pressure directly above the sea, allowing more moist air to
flow in from the surrounding areas. Due to the rotation of the Earth, bundles of cloud start rotating and an air vortex
is created. This vortex moves fast over the sea and wrecks widespread havoc on reaching the land.
How does a thunderstorm occur?
Accumulation of moisture in the atmosphere causes a thunderstorm. This occurs mostly in summer when
the sun is hot and keeps soaking up water from the ground and water bodies. The moist air rises and forms small clouds that pile up
gradually to form huge cauliflower-shaped clouds as high as 10 km. Inside the clouds, large water drops and ice crystals form due to extreme cold conditions. These remain afloat, being supported by powerful winds. When they collide and rub against one another, an electrical voltage is produced between the upper and lower layers of clouds. This voltage, once sufficiently
high, is discharged in the form of lightning.
Why is there an interval between lightning and thunder?
The reason for this is that light travels faster than sound. The speed of light is 300,000 km per second. On the contrary, sound is slow and covers only about 330 m in one second, i.e., one kilometre in three seconds. If we count the seconds till we hear
the thunder after seeing the flash of lighting in the sky and divide this value by three, we will know how many kilometres the storm is
away from us. Lighting bolts heat up the surrounding air all of a sudden-as a result thunder occurs.
Where does rain come from?
Water evaporates when the sun shines on oceans, seas, or wet grounds or when wind blows over them. The water vapour rises up and gets converted again into tiny droplets on reaching the cold heights of the sky. These tiny droplets form clouds which are carried here and there by the wind. If they rise further, such as on a high mountain crest, they become colder and turn into large raindrops, small ice crystals, and hailstones. These are heavy and fall to the ground as rain, and water seeps into the ground. This water returns to the sea as ground water,
rivers, and streams. This cyclical process is known as the ‘water cycle’.