The earth is surrounded by a layer of gas known as the atmosphere.
The weight of this air puts a pressure on the earth's surface
(the same way as your weight puts pressure on a set of scales).
We measure air pressure in millibars (mb) with a barometer.
A barograph is a barometer which draws a graph to show the
air pressure for a whole week.
Around the outside of the drum, which rotates once each week,
is a chart which a continuous record of air pressure is marked
in ink ie :-
On a weather map we join places of equal pressure with lines
called isobars eg
The weather we get from high air pressure is very different
from that we get with low air pressure ie :-
Air Pressure Questions
A.P. 1. Fill in your weather Summary Sheet for air pressure.
A.P. 2. What do we call the instrument that draws a graph
to show air pressure for a whole week ?
A.P. 3. Look at the air pressure graph at the bottom of this
page :-
a. On what day was the pressure highest ?
b. What was the highest air pressure ?
c. On what day was the pressure lowest ?
d. What was the lowest air pressure ?
What would be the best day on this graph to :-
e. go to the beach ?
f. fly a kite ?
A.P. 4. Draw an air pressure chart on graph 4 in your worksheet
to show the following information :-
Monday 1030 mb.
Tuesday 1010 mb.
Wednesday 980 mb.
Thursday 970 mb.
Friday 1000 mb.
Saturday 1020 mb.
Sunday .............990 mb.
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Assembly Area
A High Pressure Area
a
A Low Pressure Area