Geography Reference
In-Depth Information
Rn ¼ R
n
þ
R
l
n
¼
ð
1
a
Þ
F
d
þ
eF
d
reT
4
ð
6
:
2
Þ
where Rn is surface net radiation, R
n
is shortwave radiation, R
l
n
is long-wave
radiation, a is land surface albedo, F
d
is downward shortwave radiation, .e is land
surface emissivity, F
d
is downward long-wave radiation, T is land surface tem-
perature. Land net radiation is the energy source of land surface temperature
change. This study has focused on how the underlying surface change influences
land surface albedo, downward shortwave radiation, downward long-wave radia-
tion, and land surface emissivity in order to clarify the key influencing mechanism
of future land use change on regional temperature in Southern Jiangsu province
(Fig.
6.11
).
Land use change in Southern Jiangsu province mainly influences land net
radiation through exerting impacts on land surface albedo and emissivity, and land
use change influences the spatial heterogeneity of land surface emissivity most
greatly under both scenarios (Fig.
6.11
). Figure
6.11
a suggests that land surface
albedo will be the lowest in 2050 under REG scenario, while it will show no
significant difference under the other scenarios. Moreover, Fig.
6.11
b suggests that
land surface emissivity will be obviously lower in 2050 under REG scenario than
the other scenarios, under which it will show no significant difference. In addition,
Fig.
6.11
c and d indicate that there will not be significant difference in downward
long-wave radiation and downward shortwave radiation under all scenarios. In
summary, under the condition that there is no significant difference between
downward long-wave radiation and downward shortwave radiation, there will be
lower land surface albedo and emissivity in 2050 under REG scenario, which
consequently greatly increases land surface net radiation and thus lays foundation
for the warming effects.
This study analyzed the impacts of the spatial heterogeneity of land surface
emissivity on the spatial pattern of temperature in the hottest month (July) since
the difference in land surface emissivity is the main reason for the warming effects
in 2050 under REG scenario (Fig.
6.12
).
Under all four scenarios, there are always continuous districts with lower land
surface emissivity in Nanjing, Zhenjiang, Suzhou, Wuxi, and Changzhou, where
urban land is the main part of the underlying surface (Fig.
6.12
). However, the
result clearly shows that land surface emissivity in these continuous districts is
obviously lower in 2050 under REG scenario than the other scenarios, which may
be mainly because that the underlying surface will change more greatly in 2050
under REG scenario.
What's more, land surface energy budget equation suggests that under the
condition of certain land surface net radiation, the underlying surface mainly
influences temperature through influencing sensible heat flux, latent heat flux, and
soil heat flux.
