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9.1 Barometric Pressure Display
9.1.1 Viewing Absolute vs. Relative Pressure
Press and hold [RAIN/PRE] for two seconds switch between Rain and Pressure. While in Pressure mode Press
[RAIN/PRE] to switch between absolute and relative pressure
Absolute pressure is the measured atmospheric pressure, and is a function of altitude, and to a lesser extent, changes in
weather conditions.
Absolute pressure is not corrected to sea-level conditions.
Relative pressure is corrected to sea-level conditions. For further discussion of relative pressure and calibration,
reference Section 9.1.3.
9.1.2 Rate of Change of Pressure Graph
The rate of change of pressure graphic is shown to the left of the barometric pressure and signifies the difference
between the daily average pressure and the 30-day average (in inHg).
Figure 22
9.1.3 Relative Pressure Calibration Discussion
The calibration is completed on
awnet
app. To compare pressure conditions from one location to another, meteorologists
correct pressure to sea-level conditions. Because the air pressure decreases as you rise in altitude, the sea-level corrected
pressure (the pressure your location would be at if located at sea-level) is generally higher than your measured pressure.
Thus, your absolute pressure may read 28.62 inHg (969 mb) at an altitude of 1000 feet (305 m), but the relative pressure
is 30.00 inHg (1016 mb).
