Geography Reference
In-Depth Information
and built-up land, was calculated during 2005-2100. Then the transformation
thresholds were set to identify the targeted grid cells with vast changed area. In
this study, by considering the potential joint efforts to curb the deforestation in
the future that may result in reaching the saturation point of forest clearing rate,
we then set quite lower thresholds than current deforestation rate (0.7 %). The
fraction thresholds of grid cells that converted from forest land to dryland
cropland and pasture (pasture) and cropland/woodland mosaic (woodland) were
0.15 and 0.02, respectively, and the grid cells would be considered converting
from forest to pasture if both thresholds were reached. Therefore, the conversion
thresholds might have had influences on the future land surface projection.
Finally, label and replace the initial land surface map in 2005, which is pro-
cessed with USGS land cover classification at the resolution of 30 km 9 30 km
and will be used in the control experiment. By doing this, a relative reasonable
future land surface in 2100 is generated as compared with that of most resear-
ches in which replacing the entire tropical forest with cropland or savanna
vegetation types (Schneider et al.
2004
). Thereafter, a rectangle region was
selected as the study area covering the changed grid cells as many as possible
(Fig.
7.12
). High resolution with this grid size can also help to reveal the land-
atmosphere interactions as well as the cumulus parameterization and weather.
The climate forcing data is same as the data used in previous section (Sect.
7.2
boreal deforestation). The buffer zone of the lateral boundary is set to four layers
of grid points. WRF model integrates at a 5-minute step, as well as the cumulus
convection processes operation, but run the radiation process at a 0.5 hour step.
Additionally, the observations of certain climate indicators in the year 2010 are
collected for validation.
7.3.1.2 WRF Model and Experiments
The ARW-WRF is used in this study. To assess the model performance, the land
cover data and meteorology data in 2010 is used to validate the WRF model. This
model is set up with a grid of 63 9 49 cells, and each one representing a
30 km 9 30 km area, centered at 58S, 568W.
For assessing the impacts of tropical deforestation on climate change, other
variables are controlled but to modify the land surface and relative properties in
the model schemes. To achieve this goal, two experiments are designed, including
the control experiment and simulation experiment. In the control experiment,
which is regarded as the reference case, the current land surface map in 2005 is
used as the basic land cover data, maintaining constant in the whole simulation
process. By contrast, the simulation experiment is designed with the implemen-
tation of project land surface map in 2100 in which certain numbers of grid cells
are converted from the forests into dryland cropland and pasture (pasture) and
cropland/woodland mosaic (woodland) (Fig.
7.12
). This replacement will result in
changing of corresponding biogeophysical parameters, such as root depth, canopy
height, and other variables in WRF model. The climatic metrics in terms of
