METEOROLOGY

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METEOROLOGY
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SCOPE

• Clouds
• - Formation of clouds
• - Types of clouds
• Precipitation
• - Types of Precipitation
• Formation of Fog and Mist
• Wind
• - Types of Wind
• - Wind measurement

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FORMATION OF CLOUDS
Imagine a parcel of air, as example, rising up
through the atmosphere.
As the parcel rises, its humidity increases until
it reaches 100. When this occurs, cloud droplets
begin to form as the excess water vapor condenses.
Above this point the cloud droplets grow by
condensation in the rising air.
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As the earth is heated by the sun, bubbles of hot
air (called thermals) rise upward from the warm
surface. A thermal cools as it rises and becomes
diluted as it mixes with the surrounding air,
losing some of its buoyancy (its ability to rise).
An air parcel will rise naturally if the air
within the parcel is warmer than the surrounding
air (like a hot air balloon).
If a thermal is able to rise high enough to cool
to its saturation point, the moisture condenses
and becomes visible as a cloud.
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There are many ways how clouds are formed, as air
rises, into different types. Examples of those
are convection, turbulence, etc. Find out more
about the process.
Convection
Turbulence
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TYPES OF CLOUDS
- Stratus
- Cumulus
RESEARCH ACTIVITY Find out about the
features of other types of clouds and how its
formed.
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STRATUS

• - Stratus is the Latin word for layer or blanket.
• It may form a few hundred feet above the ground,
  covering a wide area, bringing generally gray
  dull weather.
• Over hills mountains, it can reach ground
  level when they are then known as fog.

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STRATUS
FORMATION OF STRATUS CLOUDS
Stratus clouds are formed when a layer of warm,
moist air rises slowly over a mass of colder air.
warm, moist air colder air Stratus clouds
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CUMULUS

• Cumulus clouds are named after the word heap.
• May formed at a range of height of 300 to 2000
  metres.
• Composed of tiny water droplets.
• Looks like heaps of cotton wool, large
  cauliflower

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CUMULUS
FORMATION OF CUMULUS CLOUDS

• Height of cloud depends on air which will only
  continue to rise if its temperature is warmer
  than the surrounding temperature.
• - May also form over sea when the sea surface
  temperature is warmer than the air passing over
  it.

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PRECIPITATION
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TYPES OF PRECIPITATION

• Rain Hail
• Freezing Rain
• Sleet
• Snow

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RAIN
Rain develops when growing cloud droplets become
too heavy to remain in the cloud and as a result,
fall toward the surface as rain.

• Can also begin its cycle as ice crystals that
  grouped together to form large snowflakes.

• Falling snow passes through the freezing level
  into warmer air which then melt and collapse into
  rain drops.

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Hail
- Hail is a large frozen raindrop produced by
intense thunderstorms, where snow and rain can
coexist.
- As the snowflakes fall, liquid water freezes
onto them forming ice pellets that will continue
to grow as more and more droplets are
accumulated.
- When the hail stone gets heavy, it fall towards
the surface as ice as the temperature below the
thunderstorm is not warm enough to melt it.
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RESEARCH ACTIVITY Find out more on how
freezing rain, sleet and snow are formed.
Freezing rain
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FORMATION OF FOG AND MIST
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FOG
Fog is composed of small tiny water droplets (or
ice crystals) which reduce visibility of Earths
surface to less than 1 km.
MIST
Water droplets in mist is smaller and fewer than
fog and visibility range is from 1 km to 2 km.
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TYPES OF FOG

• Advection fog
• Radiation fog
• Upslope fog
• Mixing fog
• Steam fog

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ADVECTION FOG Forms when moist air moves over a
colder surface and when the temperature at the
surface is below the dew point temperature of the
moving air. Common along coastal areas but
sometimes can develop inland.
Coastal fog (advection fog)
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RADIATION FOG Caused primarily by the loss of
heat by radiation during the evening and night.
Radiation Fog
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UPSLOPE FOG Air is forced to flow up a hill or
mountain, causing it to expand and cool.
Upslope Fog
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RESEARCH ACTIVITIES Find out more about
mixing fog and steam fog.
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WIND
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SCOPE

• What is wind and its application to aviation
• Coriolis Force
• Types of winds
• 4. Measurement of Wind

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What is wind and its application to aviation?

• air motion over the earths surface
• consists of vertical and horizontal movement
  (but largely horizontal)
• air moves from higher pressure region to a
  region of lower pressure

- wind speed and direction has to be taken into
consideration during take-off and landing
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CORIOLIS FORCE

• deflection of wind as a result of earths
  rotation
• directly related to the speed at which the air
  is moving and its latitude
• (higher speed more deflection
• lower speed less deflection)
• - at equator, coriolis force 0

CLICK
Demonstration of Coriolis Force
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Types of winds

• Surface wind
• Thermal wind
• Land/sea breezes
• - Gusts
• Squalls
• Gales

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Surface Wind

• wind that is blowing near the earths surface
• structure (frictional drag) of the earths
  surface determines the speed of the surface wind
• eg. Speed of wind over the sea (no obstruction)
  is faster then speed of wind through a forest
  (trees obstruct the wind movement)

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Land/Sea Breezes
2. Sea Breeze

• happens during the day when the land warms more
  rapidly than sea
• air over land surface rises, resulting in lower
  pressure
• replaced by cooler, denser air from sea
• wind flows from sea to land

1. Land Breeze

• happens at night
• air cools more rapidly over land
• becomes colder and denser than air over sea
• wind flows from land to sea

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RESEARCH ACTIVITIES
Whats the difference between gusts, squalls and
gales?
END