Geography Reference
In-Depth Information
converted from the dryland cropland and accounted for 60.55 % of the conversion
of the dryland cropland during this period.
There is no significant difference in the spatial patterns of the observed and
simulated temperatures on the whole, except some slightly large difference in few
areas. The land use/cover change in the North China Plain, which is mainly
characterized by the regional urbanization, has caused significant change of the
near-surface temperature. It led to a regional near-surface temperature rise of
0.03 C/year. Besides, the spatial pattern of the temperature change corresponded
to that of the land use/cover change on the whole, i.e., the temperature mainly
increase significantly in the regions where the urban and built-up land expanded;
In addition, the degree and range of the influence of the temperature rise varied
greatly among reasons. The temperature changed most significantly in the urban
and built-up land (0.1 C/year), followed by the irrigated cropland and pasture
(0.06 C/year). The temperature generally change by 0.02-0.05 C/year in the
forest, water bodies, and dryland cropland and pasture, and it changed most
slightly in the grassland (0.01 C/year). Among the all the types of land use/cover
change that involved a large area of land, the conversion of dry land into forest and
built-up land led to the greatest near-surface temperature increment, reaching
0.13 C/year. While the conversion of dry land and pasture into grassland made
the near-surface temperature decrease by 0.1 C/year. By contrast, the other
conversions only made the near-surface temperature change by 0.01-0.04 C/year.
In comparison to the increase of the greenhouse gases that has a global influ-
ence, the land use/cover changes exert more influence at the regional scale.
Generally, the better the vegetation cover is, the lesser will be the temperature rise.
For example, the urban heat island effect in the urban regions where there is less
vegetation will lead to greater increase of the near-surface temperature. Besides,
the temperature increment in the water bodies is generally lower, and consequently
leads to a lower near-surface temperature since the water has a large specific heat
capacity and its temperature generally increases more slowly. What's more, the
change of the underlying surface due to the urbanization can alter the physical
processes such as the energy balance of the land surface, and consequently lead to
the climate change in a large area. For example, the conversion from the cropland
to the urban and built-up land can change the roughness and albedo of the land
surface, and consequently cause the change in the radiation flux of the land surface
and lead to significant increase of the regional near-surface temperature.
Since this study is preliminary, there are still some deficiencies as follows. First,
there is still some difference between the upscaled land use/cover data and the
initial data, which leads to some uncertainties in the simulated climatic effects of
the land use/cover change. Second, the result may change if the calculus of the
data of a long period is carried out since the study of the impacts of the land use/
cover change on the temperature in the North China Plain is based on the sensi-
tivity test of the numerical integration of the data of only two years in this study. In
addition, there are some uncertainties in the result since there are various feed-
backs within the climate system.
