11.1.3.2. Diurnal Temperature Range
One important aspect of the observed temperature change over the globe during
the past century relates to its asymmetry during the day and night (Karl et
al., 1991). Observed warming in surface air temperatures over several regions
of the globe has been reported to be associated with an increase in minimum
temperatures (accompanied by increasing cloudiness) and a decrease in DTR (Hansen
et al., 1998).
AOGCM simulations with increasing concentrations of GHGs in the atmosphere
suggest relatively more pronounced increases in minimum temperature than in
maximum temperature over Asia on an annual mean basis, as well as during the
winter, for the 2050s and the 2080s—hence a decrease in DTR (Table
11-3). During the summer, however, an increase in DTR is simulated—
suggesting thereby that the maximum temperature would have a more pronounced
increase relative to the minimum temperature (Lal and Harasawa, 2001). The summertime
increase in DTR over central Asia is significantly higher relative to that in
other regions. Most of the subregions follow the same pattern of change in DTR,
except south and southeast Asia. A marginal increase in DTR during the winter
and on an annual mean basis is simulated over southeast Asia. Over the south
Asia region, a decrease in DTR on an annual mean basis and during the winter
and a more pronounced decrease in DTR during the summer are projected. The significantly
higher decrease in DTR over south Asia during the summer is a result of the
presence of monsoon clouds over the region (Lal et al., 1996). In general, the
decline in DTR is slightly moderated in the presence of sulfate aerosols (Lal
and Harasawa, 2001). Changes in DTR over Asia in this case suggest a decrease
in both seasons. Similar changes also are seen over boreal Asia and temperate
Asia.
| Table 11-3: Projected changes in diurnal temperature
range over Asia and its subregions under IS92a emission scenarios, as inferred
from an ensemble of data generated in experiments with CCSR/NIES, CSIRO,
ECHAM4, and HadCM2 AOGCMs. |
 |
| |
Greenhouse Gases |
Greenhouse Gases + Sulfate Aerosols |
| |
2050s
|
2080s
|
2050s
|
2080s
|
| Regions |
Annual |
Winter |
Summer |
Annual |
Winter |
Summer |
Annual |
Winter |
Summer |
Annual |
Winter |
Summer |
|
| Asia |
-0.15 |
-0.26 |
1.42 |
-0.27 |
-0.45 |
1.36 |
-0.17 |
-0.13 |
-0.54 |
-0.27 |
-0.26 |
-0.54 |
|
| Boreal |
-0.38 |
-0.52 |
1.67 |
-0.53 |
-0.81 |
1.62 |
-0.45 |
-0.34 |
-0.49 |
-0.57 |
-0.53 |
-0.48 |
| |
|
|
|
|
|
|
|
|
|
|
|
|
| Arid/Semi-Arid |
|
|
|
|
|
|
|
|
|
|
|
|
| - Central Asia |
0.13 |
-0.07 |
4.64 |
0.17 |
-0.11 |
4.75 |
-0.02 |
-0.14 |
2.20 |
0.09 |
-0.04 |
2.36 |
| - Tibet |
-0.34 |
-0.60 |
2.01 |
-0.46 |
-0.81 |
1.91 |
-0.53 |
-0.63 |
0.18 |
-0.67 |
-0.80 |
0.13 |
| |
|
|
|
|
|
|
|
|
|
|
|
|
| Temperate |
-0.18 |
-0.31 |
0.47 |
-0.23 |
-0.43 |
0.44 |
-0.19 |
-0.21 |
-0.83 |
-0.28 |
-0.30 |
-1.05 |
| |
|
|
|
|
|
|
|
|
|
|
|
|
| Tropical |
|
|
|
|
|
|
|
|
|
|
|
|
| - South Asia |
-0.27 |
-0.27 |
-3.06 |
-0.45
|
-0.46 |
-2.89 |
-0.22 |
-0.14 |
-4.97 |
-0.31 |
-0.31 |
-4.95 |
| - SE Asia |
0.15 |
0.24 |
-0.50 |
0.00 |
0.09 |
-0.66 |
0.35 |
0.42 |
-0.98 |
0.18 |
0.24 |
-1.09 |
|
|