The average weight of air is 1013 hectopascals (hPa). Measurements higher than this (e.g. 1020 hPa) indicate areas of high atmospheric pressure, where air is sinking. Measurements lower than this (e.g. 985 hPa) indicate areas of low atmospheric pressure, where air is rising. You can use this code to read the weather map in FIGURE2 .
FIGURE2 Weather map for 10 November
0 400 800 km
Key
1024
Isobar (value in hectopascal)
Cold front
Rainfall in previous 24 hours
Warm front
Trough
Source: MAPgraphics Pty Ltd, Brisbane
TABLE1 Symbols on weather maps for the southern hemisphere Symbol Name
What does it mean?
Comment
Isobars
Join places with the same air pressure
The closer together these lines, the stronger the wind.
High- pressure area
Sinking air
Generally ýne weather. Winds rotate around these areas anticlockwise.
H
Low- pressure area
Risingair
Generally cooler weather, rain. Winds rotate around these areas clockwise.
L
Jacaranda Humanities Alive 7 Victorian Curriculum Third Edition
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