Figure
3 An
illustration of how a small change in the mean or average value of a meteorological
variable can have a large effect on the expected number of extreme readings.
UPPER FIGURE (black curve, A): the probability of different temperature
readings when the mean temperature is 50°F. UPPER FIGURE (blue
curve, B): the same, when the mean temperature rises 5°, to 55°
F. The shape or spread of the bell-shaped pattern by which expected values
are distributed on either side of the mean is the same in both cases. LOWER
FIGURE: the corresponding changes in the probability of the temperature
readings shown on the bottom scale. The solid blue curve (with scale at
left) is the difference in probability of the readings shown on the
bottom scale. The greatest difference is for temperatures about 10°
above and below the mean value of 55°. The dashed blue curve
(scale at right) is the percentage change in probability. Readings
of 60 to 70°, for example, are expected roughly twice as often
as before.