Continued from previous page Figure. 2.2: Trends in annual
diurnal temperature range (DTR, °C/decade), from 1950 to 1993,
for non-urban stations only, updated from Easterling et al.
(1997). Decreases are in blue and increases in red. This data
set of maximum and minimum temperature differs from and has more
restricted coverage than those of mean temperature used
elsewhere in Section 2.2. Figure 2.3: Cloud cover (solid line)
and DTR (°C, dashed line) for Europe, USA, Canada, Australia,
the former Soviet Union, and eastern China (from Dai et al.,
1997a). Note that the axis for DTR has been inverted. Therefore,
a positive correlation of cloud cover with inverted DTR
indicates a negative cloud cover/DTR correlation. Since the DTR
is the maximum temperature minus the minimum temperature, the
DTR can decrease when the trend in the maximum or minimum
temperature is downward, upward, or unchanging. This contributes
to less spatial coherence on the DTR map than on maps of mean
temperature trend. Maximum temperatures h