Geography Reference
In-Depth Information
According to the statistical analysis on the downward shortwave radiation at the
grid scale, it can be found that the annual average downward shortwave radiation
will have no obvious changes from 2010 to 2050 without regarding the scenarios,
which will grow consistently from 280.4 to 282.1 W/m
2
under the CES scenario,
and that under the REG scenario will increase from 276.2 to 280.5 W/m
2
(Fig.
5.8
).
Although the Green for Grain project can reduce the downward shortwave radiation,
the urban area expansion will lead to more downward shortwave radiation, and that
is why there is a higher increment of downward shortwave radiation under the REG
scenario. On comparing the downward shortwave radiation under two different
scenarios, it can be seen that it is higher under the REG scenario than that of under
the CES scenario in the period of 2010-2050. The spatial distribution of downward
shortwave radiation in 2030 and 2050 under the REG scenario represents that the
area, whose downward shortwave radiation is less than 265 W/m
2
, is expanding
especially in the northern and middle region and the western part of the semiarid
grassland area of China due to the ecological recovery (Fig.
5.8
). For example, the
barren or sparsely vegetated lands are improved to be grassland gradually.
5.2.6 Concluding Remarks on Biogeophysical Effects
of Green for Grain Project
This study applies the DLS model to simulating the land cover distribution from
2010 to 2050 under the CES scenario and REG scenario, and then analyzes the
effects of land cover change on the regional energy balance in the semiarid grassland
area of China through implementing the numerical simulation with the WRF model.
Latent heat and radiation are the main factors influencing the energy balance, so this
study selects two indexes including latent heat and downward shortwave radiation
to explore the energy balance in the study area. The conclusions are as follows:
(i)
There will be no significant change in the spatial pattern of the land cover in
the study area during 2010-2050. The changing ratio of all the land cover
types will show a decreasing trend with time. Under the CES scenario, the
grassland shows an increasing trend, while the forest cover is shrinking
because the harsh natural conditions restrict the forestry area expansion, and
shrubland accounts for the largest percentage of the newly increased forest
cover. Barren or sparsely vegetated land will be mainly converted to
grassland or shrubland. During the period of 2010-2050, there will be an
increase in urban area under the REG scenario, and the main land cover
converted to urban area is cropland. Compared to the CES scenario, the rate
of increase of grassland will be lower, and the expansion of grassland is
mainly concentrated in the western part of Loess Plateau.
(ii)
The simulation results indicate that there will be no obvious changes in
energy flux of near surface under the CES scenario, and the latent heat flux
and downward shortwave radiation will all have small-scale increase.
