2. •Convection is the
heat transfer which
takes place due to
the actual
movements of
particles of the fluids.
•This type of heat
transfer takes place
only in liquids and
gases.
3. 5.As air rises through
the surrounding
regions of greater
density, it begins to
cool & contract,
becoming more
dense. 1.Solar energy reaches
Earth’s surface through
4.Warmer, less dense radiation.
air rises carrying the
heat upward by
convection. 2.Energy is absorbed by
3.The heat energy of the surface Earth’s surface causing it to
is transferred by air in contact warm.
with this surface by conduction.
A diagram explaining all the 3 methods
of heat transfer involved in the air
circulation.
4. •Convection currents are
those rising flows caused
by heating or falling flows
caused by cooling in
liquids or gases.
•In air a rising current may
be caused by local heating
from dark soil or heated
buildings.
5. •Convection currents
caused by cooling are
much less obvious, but
take place in the upper
atmosphere when
heated air is carried up
and instead of levelling
out in a layer cools and
falls.
6. How can we
explain why
warm air rises ,
by the method
of convection?
Here’s How..
NEXT
7. RETURN FLOW
WARM SEA BREEZE COOL
RETURN FLOW
LAND BREEZE
COOL WARM
Local heating can cause a local wind as air flows in to replace the rising
heated air. It can be seen at a lake or sea shore where a daily onshore
breeze occurs as the land heats faster than the ocean in the morning
and a daily off shore breeze as the land cools faster than the ocean.
8. Convection currents become critical in making winds
when warm moist (high humidity) air rises and cools.
Condensing water vapour in the cooling air gives off a
lot of heat which drives the core area with droplets of
water higher while cool air flows outward and down.
This produces huge thunderheads of clouds with
moisture forming larger and larger drops which make
static electricity and lightning. Under the right
conditions rotation can occur from the effects earth's
rotation and a tornado or hurricane can result.
