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Precipitation
Essential Questions.
What is Precipitation?
How is precipitation formed?
What are the processes involved in forming
precipitation?
What are the different types of Rainfall?
Why are there different types of rainfall?
What is Precipitation?
Precipitation is the primary mechanism for
transporting water from the atmosphere to the
surface of the earth.
There are several forms of precipitation, the
most common of which for the United States is
rain. Other forms of precipitation include; hail,
snow, sleet, and rain.
Rain
Sleet
Snow
Hail
Conditions necessary for rain to form
• Presence of water / water vapour
• Heat – evaporation
• Cooling – dew point –
condensation
• Cloud formation
Processes involved in the formation
of rain
Gaseous State
Liquid state
Types of rainfall
1. Convectional Rain
2. Relief Rain or Orographic Rain
Convectional Rain
Warm air cools down and
water vapor condenses to
form water droplets
forming clouds. The cloud
become saturated with
water droplets.
Rainfall takes place
Warm Air Rises
called Convectional together with water
Rain
vapour
Heat is radiated
from the ground
to the air
The ground absorbs the Sun’s Heat
rays and becomes heated
Heat rays from
the Sun
Relief or Orographic Rain
Relief or Orographic Rain
Moisture condenses as the
air cools (7oC) at high
altitudes (2000m) to form
clouds. Clouds become
saturated with water
High
mountain
Prevailing
Wind
Moist & warm air from
the ocean (20oC)
Ocean
Windward side
of Mt
Cool & dry air
descends the leeward
side of mountain,
resulting in a dry and
warm climate
Leeward side of
Mt
Questions?
1. What is an important factor necessary for
Convectional and Relief rain to form?
2. What type of rain would Singapore commonly
experience?
3. Other than this type of rain, what other forms of
rain does Singapore experience? (Hint, Nov and
Dec are generally wetter, why?)
4. Name some locations where Relief rain is
commonly experienced? (Hint Mountain ranges
that face the oceans)
My journey in becoming a self-regulated
learner?
• Do you know what is the learning target for
this lesson? ( Do you know what your need to
understand – knowledge & skill)
• Can you go thru the slides and think about
what you are reading and listening?
• Do you have questions as you learn?
• Do you know what you have learnt , un-learnt
and re-learn?
Winds
Essential Questions
What is wind?
How is wind formed?
What are the different types of wind?
What are the different scales of wind?
What is wind?
Wind is simple the flow of a huge amount of air,
usually from a high pressure area to a low
pressure area.
Warm air rises (lighter/Less dense)
Parcel of Cold air (high pressure)
sinks as it is denser
Parcel of Warm air (low pressure)
How is wind formed?
You may use annotated diagrams to explain.
Some points to get you started:
1. Rate of heating of solids and liquids?
1.1What experiments can you design to show
the differing rates of heating of solids and
liquids?
2. Warm air rises… Cold air ….
2.1 Design an experiment to prove that warm air
rises and cold air sinks. Develop an explanation
for this.
What are the different types of winds?
There are mainly …..
1. Local Winds
2. Planetary / Global Winds
What are Local Winds?
• Local winds are those that are created as a
result of scenery such as mountains,
vegetation, and water bodies. They usually
change very often and the weather forecast
people talk about this kind on the TV everyday.
They can move from mild to extreme winds in
just hours. Good examples of local winds are sea
breezes and land breezes, and mountain and
valley breezes. Local winds cover very short
distances and are on a small scale.
Formation of Sea Breeze
As it is less
dense (low
pressure)
Air gets
heated
and rises
LP
Land gets
Heated
Sea Breeze
HP
Cool air is denser
(high pressure) and
sinks to stay close to
the surface of the
water
The air above
the sea is also
cooler compared
to the air above
the land
The Sea (liquid) is a poorer
conductor of heat and thus it
is cooler .
Now it’s your turn
With the help of an annotated diagram, explain
how land breeze is formed. (p.51?)