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The Water CycleWater is constantly moving between sea, air and land
The sun shines and
the sea is heatedh
eat
The Water CycleWater is constantly moving between sea, air and land
Evap
ora
tio
n
The water
evaporates and
forms clouds
The Water CycleWater is constantly moving between sea, air and land
Condensation
As air rises it cools
and condenses. It
reaches the
ground as rain,
snow, sleet or hail.
The Water CycleWater is constantly moving between sea, air and land
The snow
melts and
flows
Lakes
form
Snow forms
HumidityIt is the amount of water vapor in the air .
The higher the temperature the more water vapor it can hold
Warm air can absorb much more water vapor than cold air
Relative HumidityThe amount of water vapor in the air compared to the total amount that air can hold at that temperature .
When water can’t hold water vapor anymore the relative humidity is 100%
• When the air is saturated or filled with water vapor ,any additional water vapor will condenses in to a liquid ….This temperature is called “Dew point “
Naming clouds• we can call the clouds according to their altitude by
adding prefix or suffix.
Example:
Prefix “Cirro “ Clouds formed at high altitude
“Alto “ Middle altitude
“Nimbo” They are clouds bringing thunder storm
Suffix Nimbus They are clouds bringing thunder storm
2) Sleet• Forms when raindrops freeze and turn into pellets of ice before falling
to earth’s surface.
Snow • It falls when the air becomes cold that water vapor becomes solid rather than condensing
into droplets
Measuring amount of rainfall
• People have measured rainfall for thousands of years.
• It is especially important for farmers to know how much rain will fall this year.
• The instrument used to measure rain fall is called “Rain Gauge”
Thunderstorm• It begins to from when warm humid air moves upwards rapidly
• The sun heats a place on Earth’s surface ,which , in ,turn , warms the air mass above it.
• Then a cold front may push under the warm air mass , or wind may force it upward.
• The higher surrounding air is colder than the rising air mass.
• As the warm air cools, the water vapor in it condenses into air droplets, which forms a cloud
• Soon the water droplets become heavy enough to fall as rain .
• The falling rain pulls in cool air with it.
• Winds blow both upward and downward in the cloud .
• Negative electric charges build up in the bottom of the cloud.
• The charges travel through the air in a lightning discharge .
• The air along the path of a lightning bolt extremely hot
• The air along the path of a lightning bolt extremely hot
• The intense heat makes the air expand so fast that sound waves are produced .
Tornado • It is a violently rotating column of air that extends
downward from thunderclouds and touches the ground.
• A tornado starts when winds spin a column of air that bulges from the bottom of the cloud .
• Strong updrafts ,or rising air ,are already present inside this bulge.
• Next warm, humid air is pulled into the often funnel-shaped column.
• The air spins so fast that an area of very low pressure forms in the center.
• The swirling funnel starts to descend.
• Because of the low pressure air in the near by area rushes into the funnel.
• The air in the funnel rotates upward around the center, joining the storm above.
• The wind speed in the tornado can reach 400km/hr or more.
What is a hurricane?
A hurricane is a very destructive and dangerous
storm. It forms in stages. The hurricanes are filled
with rain, strong winds, lightning, thunder, hail
and tornadoes.
Stages of the hurricane :
1)Tropical depression
2)Tropical storm
3)Hurricane (wind speed 120km/hr)