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YOUNG SCIENTIST SECTION
H ow t o re ad
the clouds ?
BY Wee Kin Guan
GRAPHIC: PEI XIAN
Whenever you look at the sky, it is very likely that you will be
able to see some clouds. These amazingly shaped clouds that
you see are a great example of how beautiful nature is.
Apart from being inspired by the beauty of the clouds, many
people in the world study clouds extensively to understand
them better and make use of the knowledge acquired.
The study of clouds belongs to the clouds physics branch of
meteorology (the study of the atmosphere). Humans started
to record their observations and speculations of clouds a few
thousand years ago, and one of the earliest examples can be
traced back to ancient India, where one of the writings of the
3000 B.C. era discussed the processes of cloud formation.
Aristotle is considered as the founder of meteorology for his
treatise Meteorology, written around 340 B.C. The modern
study of clouds with the knowledge of physics was developed
in the 19 th century, and it continues today.
On Earth, clouds are made of condensed water or ice. These
water droplets and crystals are suspended in the atmosphere
above Earth’s surface, usually in the troposphere, the lowest
portion of the atmosphere.
One important question emerges: How do clouds form? The
answer is all about the air and water vapour. The rising air
from the Earth’s surface contains water vapour.
The atmospheric pressure decreases with altitude, and this
drop in pressure causes the air to expand, lose energy and
cool down in the process.
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The amount of water vapour
that air can retain depends
on the temperature of the
air. Some of the water vapour
is released from the cooled
air and forms visible water
droplets or crystals. These
visible masses of water are
what we know as clouds.
Due to the complexity of
the cloud formation, no
two clouds are identical in
terms of shape and height.
However, we are able to
categorise the clouds in
simple groups, thanks to
British meteorologist, Luke
Howard.
He devised a system for
naming clouds in 1801 and
was honoured with the title—
‘The father of meteorology’.
He named the clouds based
on Latin root words, which
indicate the appearance and
level of the clouds in the
atmosphere.
The success of Howard’s system
was due to the universal usage
of Latin and the flexibility to
change the names.
Middle
altitude
clouds
English Heritage Blue at
Tottenham, London
T h e re a re t h re e g ro u p s
fo r
a p p ea ra n ce :
cirrus
( c u r l o f ha i r ) , s tra t u s
( l aye r )
and
cumulus
( p i l e ) . A d d i ti o n a l l y, t h e re
a re
t h re e
p re fi xe s
to
i n d i ca te t h e l eve l o f t h e
c l o u d : c i r ro - i s u s e d fo r
h ig h c l o u d s (a b ove 6,0 0 0
m e tre s ) . T h e p re fi x a l t o re fe rs t o m i d - l eve l c l o u d s
( b e t w e e n 2 ,0 0 0 a n d 6,0 0 0
m e tre s ) . A n d t h e n a m e s o f
l o w - l eve l c l o u d s u s u a l l y
h ave s tra t o - ( f l a t l aye r )
o r n i m b o - ( ra i n c l o u d s ) a s
t h e i r p re fi xe s . Co m b i n i ng
t h e p re fi xe s a n d g ro u p
n a m e s , w e a re a b l e t o
classify the clouds into
t e n ca teg o ri e s i n H o wa rd ’ s
s y s te m .
At this height, clouds are
composed of water droplets
and occasionally ice crystals.
Cirrus:
thin and hair-like, sometimes
called “mare’s tail”.
Cirrostratus:
sheet-like, nearly transparent
and covers a large part of the
sky. The Sun may appear to
have a coloured halo when
shining through a large sheet of
cirrostratus.
Altocumulus:
Puffy clouds, appear like dozens
of small, loose bands. This may
indicate impending rain.
High altitude
clouds
The clouds at high altitude
contain
ice
crystals
as
water always freezes at
that altitude. They usually
represent fair weather as
they do not bring rain.
Cirrocumulus:
small and patchy, consists of
many small clouds in the form
of grains or ripples. A sky with
cirrocumulus is sometimes called
‘mackerel sky’ for its scale-like
appearance.
Altostratus:
Thin and uniform, diffused with
little appearance of individual
clouds. This can bring rain or
snow.
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Low altitude
clouds
Clouds at a low level are
composed of water, and
often indicate fair weather
or drizzle.
Stratocumulus:
Wide and flat at the bottom,
and puffy at the top,it has both
layered and lumpy features. It
can produce very light rain (drops
that are usually greater than 0.1
cm in diameter) or drizzle (drops
with diameters less than 0.1 cm).
Cumulonimbus:
Often called ‘thunderhead’, this
type of cloud generally produces
thunderstorms, rain or showers.
This is most common in warm
and humid weather.
Now you have understood how
to read the clouds, why don’t
you try and identify these
clouds?
A
Vertical
clouds
associated
These kinds of clouds are
developed vertically and likely
to grow beyond the boundaries
between Howard’s cloud levels.
They often produce rain, snow
or thunderstorms.
A: (Answer - cirrocumulus)
Cumulus:
Puffy cloud often
with fair weather.
B
B: (Answer - cumulus)
C
Stratus:
Flat and uniform in all directions,
often obscuring the sun so that
the sky looks grey or white. This
may bring drizzle.
Nimbostratus:
A layered, uniform rain cloud. Its
appearance is very dark, and and
it tends to bring long-lasting
rain.
C: (Answer - cumulonimbus)
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