Geography Reference
In-Depth Information
4.3.1 Method and Data Processing
4.3.1.1 Model and Experiment Design
With the development of the atmospheric models and land surface process models,
the numerical simulation has become a widely used approach to study the influ-
ence of climate on vegetation. WRF model has been widely used in the global
climate and achieved good simulation result, and we use the ARW-WRF (Edition
3.3) in this study.
The location and size of the simulation area have great influence on the sim-
ulation result (Seth and Giorgi,
1998
) The center line of the simulation area was set
to be 36 N, 117 E in this study. The Lambert projection was used, with the two
standard parallels being 26 and 46 N, respectively. The spatial resolution was set
to be 20 km, and there were 112 grid points in the east-west direction and 97 grid
points in the north-south direction in the whole simulation area.
The lateral boundary forcing data, that came from the NCEP/FN dataset, are
updated every 6 h. This dataset has the spatial resolution of 1 9 1 and the vertical
height of 27 layers, and it has been established and updated since July of 1999 with
the data assimilation of almost all kinds of observation data (e.g., remote sensing
data and ground-based observation data). In comparison to the datasets of NCEP I,
NCEP II, and EAR40, the NCEP/FNL dataset has higher accuracy and spatial
resolution, and it includes more kinds of environmental variables.
In the parameterization scheme of physical processes in the model, the cumulus
parameterization scheme adopted the Grell-Devenyi ensemble scheme, the
boundary layer process scheme was YSU, and the shortwave radiation scheme was
the CAM scheme, while the land surface process scheme was Noah land surface
model. The boundary buffer was set to be four layers of grid points, and the
boundary conditions adopted the relaxation scheme. The time interval of the model
integration was set to be 5 min, and that of the radiation process and cumulus
convection was 30 and 5 min, respectively. There were 27 layers in the vertical
direction and the atmospheric pressure at the top layer was 50 hPa.
The test scheme in this study is as follows (Table
4.3
). There are two sets of
tests, one is the control test and the other is the sensitivity test. The land cover data
of 1985 is used in the control test and that of 2005 is used in the sensitivity test.
The two tests are both implemented with the climate forcing data between October
of 2005 and December of 2007.
4.3.1.2 Processing of Land Cover Data
It is necessary to reclassify the land use/cover data with the USGS land cover
classification, which includes 24 land-cover and land-use types and set the spatial
resolution to be 20 km according to the requirement of the WRF model. Therefore,
the land use/cover data of the IGBP land cover classification are first reclassified
with the USGS land cover classification system, and then the spatial resolution of
