Weather and Climate

GE2201 Terrestrial Environments

Web Quest 1

1 ©Timothy Tan Xin Zhong, TBJ

Timothy Tan Xin Zhong (17) M07205

Terrestrial Environments Web Quest 1

“I've lived in good climate, and it bores the hell out of me. I like weather rather than climate.”

John Steinbeck

Part 1

1. Define weather and climate. "Climate helps you decide what clothes to buy; weather helps you decide what clothes to wear."

Anonymous

Weather

Weather is the day-to-day state of the atmosphere, and its short-term (minutes to weeks) variation.

It refers to the general mix of events daily in our atmosphere such as its temperature, pressure, water content, rainfall and humidity.

It is also the instantaneous state of the atmosphere, or the sequence of the states of the atmosphere as time passes.

It is also the state of the atmosphere at any place at any moment. Everyday, weather events are recorded and predicted by meteorologists. (www.abclocal.go.com)

Climate

Climate is usually defined as an ensemble of all the states of the atmosphere at a place experienced in the course of some large but finite time interval (approximately 30 years) and controls the weather.

It is defined as statistical weather information that describes the variation of weather at a given place for a specified interval. It represents the synthesis of weather of a locality averaged over some period plus statistics of weather extremes.

It is also the average weather pattern in a place over many years.


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2. Explain what air pressure is and how it is formed.

"In Korea, General Van Fleet publicly surmised that more air pressure might force the Reds to

sign a truce.” Today Newspaper

(www.hko.gov.hk)

Definition of air pressure

Atmospheric pressure refers to the pressure at any point in the Earth’s atmosphere.

Atmospheric pressure is defined as the force per unit area exerted against a surface by the weight of the air above that surface. In the diagram below, the pressure at any point “X" increases as the weight of the air above it increases and vice versa.

(/ww2010.atmos.uiuc.edu/ (Gh)/guides/mtr/fw/prs/def.rxml)

If the number of air molecules above a surface increases, there are more molecules to exert a force on that surface and thus, the pressure increases.

How is air pressure formed?

Air pressure is the force exerted on you by the weight of air molecules. Although air molecules cannot be seen, they still have weight and take up space. Since there is space between air molecules, air can be easily compressed to fit in a smaller volume.


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3. Name the instrument used to measure air pressure and the SI unit to measure air pressure.

“Well we can try to measure democracy, just as you measure temperature with a thermometer or

air pressure with a barometer. “ Hugo Chavez

The barometer

m

Atmospheric pressure is measured with an instrument called a barometer, which is why atmospheric pressure is also referred to

as barometric pressure.

(www.stuffintheair.com)

The Pascal

The Pascal (Pa) is the SI (International System of TiUnits) unit of pressure or stress. It is equivalent to one Newton per square meter. In everyday life, the hectopascal (1 hPa

= 100 Pa0 is most commonly used. One hectopascal corresponds to about 1‰ of atmospheric pressure (near sea level).

4. Explain the formation of wind

Kites rise highest against the wind, not with it.” Winston Churchill

As the earth is affected by unequal amount of heat energy from the sun, the state of the

air would differentiate between different regions. Warm air expands and thus rises

up while cold air condenses and sinks, resulting in the flow of air and thus forms

wind. In meteorology, wind means the horizontal motion of airflow.

(Okanagan University College)


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(www.ww2010.atmos.uiuc.edu)

5. Name three most commonly seen types of clouds

“I can't change the direction of the wind, but I can adjust my sails to always reach my

destination.” Jimmy Dean

There are three general cloud types. If you were to look into the sky this very minute, you might

see a cloud that doesn't look like the stratus, cumulus or cirrus clouds described below. Clouds

are a combination and variations of the three general types.

Cirrus Clouds Description: Thin, feathery and wispy

Cirrus clouds are a third general type of cloud and the most common

form of high-level clouds found at heights of approximately 6,000

meters. The word cirrus comes from the Latin word for a tuft or curl

of hair. Cirrus clouds are composed of ice crystals from the freezing

of super-cooled water droplets and are so thin that sunlight can pass


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right through them. They generally occur in fair weather and face toward the direction of air

movement at their elevation.

Stratus Clouds

Description: Horizontal, layered, low and gray

The word stratus comes

from the Latin word that

means "to spread out."

Sometimes a layer of warm

and moist air passes over a

layer of cool air. Stratus

clouds often form at the boundary where these layers meet. If

the layers of air are very large, the stratus clouds may extend

across the sky. Fog is status clouds at ground level. Stratus

clouds bring rain or snow.

Cumulus Clouds

Description: Puffy, large cotton balls, flat bottoms and are low in the sky

The word cumulus comes from the Latin word for

a heap or a pile. Cumulus clouds usually form

when warm, moist air is forced upward. The

clouds that produce heavy thunderstorms in

summer are a form of cumulus clouds called

cumulonimbus. Cumulonimbus clouds may extend

upward for hundreds of meters. If they grow tall,

they can become thunderheads and bring rain.

Credits:

� http://www.cityofportsmouth.com � http://schoolscience.rice.edu/duker/weatypeclouds.html

� http://thinkexist.com/quotation/i_can-t_change_the_direction_of_the_wind-but_i/212145.html


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(http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/prcp/home.rxml)

6. Name the 4 most common types of precipitation

Prevention of birth is a precipitation of murder” Tertullian quotes

When cloud particles become too heavy to remain suspended in the air, they fall to the earth as

precipitation. Most precipitation starts off as snow as the temperature at which the cloud exists

is usually below freezing. There are different types of precipitation depending on what the

vertical temperature profile is. Some examples include Rain, Freezing Rain, Snow, Hail, Sleet,

Drizzle, Fog, Glaze, Rime and Mist.

Rain

Description: drops of water that fall from clouds and have

a diameter of about 0.5mm.

Rain occurs when tiny cloud droplets collide to form

bigger droplets. This keeps happening until the droplet is

two heavy for the air to support it and thus, is not able to

remain in the cloud. The droplet then begins to fall,

colliding with more cloud droplets as it gains in size and

falls to the ground. Rain can also begin as ice crystals that

collect each other to form large snowflakes. As the falling

snow passes through the freezing level into warmer air, the flakes melt into rain.


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Snow

Description: an aggregate of ice crystals

Snow is ice that falls from the sky. Each snowflake is a delicately

complex arrangement of ice crystals. A snowflake forms when water

vapor sublimates. Snow occurs when the layer of the atmosphere

from the surface of the earth through the cloud is entirely below

freezing. The precipitation falls from the cloud as snow and does not

melt at all while falling to the ground. The diagram below shows a

typical temperature profile for snow with the red line indicating the

atmosphere's temperature at any given altitude.

(http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/prcp/snow.rxml)

The vertical line in the center of the diagram is the freezing line. Temperatures to the left of this

line are below freezing, while temperatures to the right are above freezing. Since the snowflakes

do not pass through a layer of air warm enough to cause them to melt, they remain intact and

manage to reach the ground as snow.

Hail

Description: Hail is a large frozen raindrop produced by intense thunderstorms, where snow and

rain can coexist in the central updraft. Its size can range from pea-sized to the size of a softball or

even larger.

Hail is ice that falls from the sky, often in round shapes. Hailstones form as a byproduct of strong

updrafts that exist in thunderstorms within intense thunderstorm clouds when upward moving air

keeps pellets of frozen water from falling. The hailstone will "cycle" through the cloud and

updrafts will cause it to rise and gravity will cause it to fall. While this is occurring the hailstone

is picking up more moisture and growing in size. Eventually the balls of ice become too large

and heavy for the updrafts to keep it suspended and it will fall to the ground as hailstones. The


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hail stone reaches the ground as ice

since it is not in the warm air below

the thunderstorm long enough to

melt before reaching the ground.

(Photo by: NSSL)

Sleet

Description: Sleet is like slush falling from the sky and is usually smaller and wetter than

hailstones. It causes surfaces to become very slick, and is easily visible.

Sleet is nothing more than frozen raindrops. Sleet

occurs when there is a warm layer of air above a deep

sub-freezing layer at the surface. The layer above

freezing will allow for liquid precipitation but as the

drops hit the cold layer, they will freeze and hit the

ground as frozen water droplets. Sleet usually doesn't last

long and mainly occurs ahead of warm fronts during

winter months.

(www.weatherbook.com)

The diagram below shows a typical temperature profile for sleet with the red line indicating

atmospheric temperature at any given altitude.

(http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/prcp/snow.rxml)


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Sleet is less prevalent than freezing rain and is defined as frozen raindrops that bounce on impact

with the ground or other objects. The vertical line in the center of the diagram is the freezing

line. Temperatures to the left of this line are below freezing, while temperatures to the right are

above freezing.

7. Explain how rain is formed.

“In our lives there is bound to come some pain, surely as there are storms and falling rain; just

believe that the one who holds the storms will bring the sun.” Anonymous

Formation of Rain-clouds

Description: Contain huge numbers of tiny droplets of moisture.

“Have you not seen how God drives along the clouds, then joins them

together, then makes them into a stack, and then you see the rain come

out of it? And He sends down from the sky mountain masses (of clouds)

with cold hail in them, striking with it anyone He wills and averting it

from anyone He wills. The brightness of His lightning almost blinds the

sight.” The Qur'an, 24:43

Rain clouds are formed and shaped according to definite

systems and stages. The formation stages of

cumulonimbus are as follows:

1. Being driven along: Clouds are carried along, that is, they are driven

along, by the wind.

2. Joining: Then, cumulus clouds driven along by the wind join together,

forming a larger cloud and thus increasing the updrafts within the cloud.

3. Stacking: The updrafts near the centre of the cloud are stronger than

those near the edges. These updrafts cause the cloud body to grow vertically, so

the cloud is stacked up. This vertical growth causes the cloud body to stretch

into cooler regions of the atmosphere, where drops of water and hail formulate

and begin to expand.

Formation of Rain

Description: Formed when tiny droplets are enlarged, first by moisture from the surrounding air

condensing on them and then by coalescing with other droplets during their descent.

The formation of rain takes place in three stages. First, the "raw material" of rain rises up into the

air with the wind. Clouds are soon formed, and raindrops will then appear. The Qur'an's account


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of the formation of rain refers exactly to this process. In one verse, this formation is described in

this way:

“It is God who sends the winds which stir up clouds which He spreads about the sky however He

wills. He forms them into dark clumps and you see the rain come pouring out from the middle of

them. When He makes it fall on those of His slaves He wills, they rejoice.” The Qur'an, 30:48

FIRST STAGE: “It is God who sends the winds..."

Foam bubbles of the oceans continuously burst and

cause water particles rich in salt to be ejected towards

the sky to be carried away by winds and rise upward

into the sky. These particles, called aerosols form cloud

drops by collecting around the water vapor

themselves, which rise from water bodies as tiny droplets.

SECOND STAGE: ".... which stir up clouds which He

spreads about the sky however He wills. He forms

them into dark clumps..."

Clouds are formed from water vapor that condenses around the salt crystals or dust particles in

the air. Because the water droplets in these clouds are very small, the clouds are suspended in the

air, and spread across the sky. Thus, the sky is covered in clouds.

THIRD STAGE: "…and you see the rain come pouring our from the middle

of them"

The water particles that surround salt crystals and dust particles slowly

thicken and form raindrops as they start to grow and become too heavy and

thus drop down onto Earth as rain.

(www.urbanstone.smugmug.com)

Weather and Climate

Documents

warm air

flow of air

cold air

pressure increases

weight of air molecules

number of air molecules

anonymous weather weather

layer of cool air