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METEOROLOGY FOR EVERYONE |
Prepared by: Dr. Ahmet KILIÇ
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AIR MOISTURE |
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THE WORLD 'S WATER |
There is moisture present in air. There are
various forms of moisture, such as solid,
liquid and gas. Atmospheric moisture plays a
significant role in weather when it changes
from one state to another. These changes,
condensation, cloud, fog, dew and frost
precipitation (rainfall and snow).
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WHAT IS HUMIDITY ? |
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EVAPORATION AND
CONDENSATION |
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THE WORLD'S WATER
The World' s water About 70% of the Earth is
covered with water. Most of this lies in the
oceans. The Pacific Ocean alone covers
almost half the world. Much of the rest of
the water is in the ice sheets, glaciers and
underground. There are 3 forms of water in
the air:
1. The gas, water vapour.
2. Liquid water, droplets.
3. Solid, ice crystals. It changes from one
form to another by evaporation, freezing,
melting and condensation.
The Water Cycle
No new water is ever made. The rain you see
has fallen millions of time before. In
the water cycle the water on the Earth is
used again and Gain.
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WHAT IS HUMIDITY ?
The measure of the water vapour content in
the atmosphere is called humidity. All air
contains some water vapour but the amount
varies greatly. Warm air can hold more water
vapour than cold air. As a result, when the
humidity is high, the weather is humid. When
the humidity is low, the weather is dry.
How do we
measure relative humidity?
We use a
hygrometer to measure the relative humidity
of the air. A hygrometer consists of a
dry-bulb thermometer and a wet- bulb
thermometer. One end of the wet- bulb
thermometer is covered with wet muslin.
Evaporation of water from the wet bulb
lowers the temperature. When the air is dry,
more water will evaporate and the wet-bulb
thermometer will show a lower reading. The
difference in the readings of the two
thermometers tell us the relative humidity
of the air. Relative humidity is expressed
as a percentage (%). On very wet days,
relative humidity may be 100%. When the
relative humidity is at 100%, the air is
saturated. If there is any excess water
vapour, condensation will take place. |
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Relative humidity:
Relative
humidity is a measure of the amount of water
in the air compared with the amount of water
the air can hold at the temperature it
happens to be when you measure it.
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EVAPORATION AND CONDENSATION |
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The Sun heats the oceans and lakes and
millions of gallons of water rise into the
air as invisible water vapour. This is
called evaporation.
As the vapour rises, it cools and turns back
into liquid water. This is called
condensation.
It falls as rain and snow and is carried
back to the ocean by rivers and streams.
Then the cycle begins all over again.
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Amount
of liquid water remains constant as evaporation and
condensation cancel each other out.
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Amount
of liquid water in puddle increases as condensation
exceeds evaporation.
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Amount
of liquid water in puddle decreases as
evaporation exceeds condensation.
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Condensation.
There are two major types of condensation. One is
present on the surface of objects, such as dew and
frost. The other one is suspending in air, such as
clouds and fog. Clouds are made up of millions of tiny
water droplets, formed when air is cooled. They are
formed in several ways and are named according to their
shape, height and size. Clouds help to forecast the type
of weather, which may follow. They are often associated
with precipitation ( rain, snow, sleet or hail), but not
all clouds lead precipitation. |
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