The Water Cycle

•To understand the processes involved in the water cycle

What is Evaporation?•It is the process of a liquid heating to form a gas

What is Condensation?

•It is the process of a gas cooling to form a liquid

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

The Water Cycle is complete

What is humidity ?

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 “

Types of Clouds

1)StratusBlanket Like

2)Cumulus• Billowy puffy clouds that seem to rise from flat bottoms

3)Cirrus• They are wispy feather like .

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

Alto stratus Prefix

Cumulo nimbus Suffix

Examples

Cloud Cover

Types of cloud

Types of precipitation 1)Rain

It falls when the temperature is warm .

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

Hail stones • As wind pushes raindrops high into the atmosphere where they turn

into ice.

• The process repeat as water freezes in layers and the hail stone grow.

Clouds and weather

•Puffy cumulus cloud They often appear in fair weather .

•Wispy cirrus cloud Change in weather is happening

Darker stratus

Forecast

Precipitation

Nimbocumulus

Large Cumulus Clouds

• Heavy rain or snow showers which ends quickly.

Stratus cloud

• Long lasting precipitation with smaller raindrops and snow flakes

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 when intense heat causes air to rise quickly (low

dense air )

• This heated air ,or updraft, then cools and forms clouds.

• Updrafts hold water droplets and ice crystals in the cloud.

• When they grow too heavy for the updrafts to support , they fall as rain or hail.

• As the precipitation falls many of the raindrops and ice crystals collide (hit each other) .

• Downdrafts in the cloud also cause falling air to brush against rising air .

• This results in the formation of electric charge at the bottom of the cloud .

• (Negative electric charges build up in the bottom of the cloud.)

• When enough of a charge builds up ,it produces a huge spark ,which is called “lightning “ .

• Lightning superheats the air around it ,where air expands suddenly (spread out ) then contracts as it cools.

• This rapid movement of air produces sound waves that are heard as “thunder “

Tornado • It is a violently rotating column of air that extends

downward from thunderclouds and touches the ground.

• A tornado starts when moist hot air mixes with cold dry air .

• On hot days ,rising air (low density) causes powerful updrafts .

• The air begins to spin in the cloud ,if the updraft is strong air rushes with high speed decreasing the pressure at the center.

• As more air rushes in ,the air pressure at the center decreases more and more ,increasing the spinning speed .

• Soon a funnel forms that may reach the ground

• The swirling funnel starts to descend.

• The wind speed in the tornado can reach 500km/hr or more.

• The force of the tornado ‘s winds destroy houses , cars and anything in its path.

Hurricane

It is a large ,rotating tropical storm system with wind speeds of at least

119km/hr

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)

• It starts as thunderstorm over the ocean near the equator .

• The heat causes air above the ocean to be warm with low pressure ,and evaporation of the water (area of tropical depression)

• As the water vapor rises up , the temperature decreases causing it condensation and release of energy causing the warming of air that causes the decrease in density more and more.

• AS the air pressure falls ,the wind grow stronger when winds near the center reach 120km/hr the storm is considered hurricane .

• Hurricanes produce huge amount of rain .

What is eye of a hurricane?

While some hurricanes, are

small, others can be quite

large. Hurricanes are mighty

storms.

In the center of a hurricane

is an eye. Ironically, the eye

is actually a calm area in a

hurricane.