Geography Reference
In-Depth Information
directly alters the solar radiation absorbed by land surface, subsequently leads to
the change in the long-wave radiation of land surface into space and sensible heat
and latent heat, and finally influences the temperature (Chapin et al.
2005
). Some
of the key work demonstrating the sensitivity of climate to land surface albedo was
performed by Charney et al. (
1975
). Without regard to the influence of advection
process, the increase will lead to the decrease of the solar radiation absorbed by
land surface, increase the land surface temperature, subsequently increase the
long-wave radiation into the space and decrease the sensible heat and latent heat,
and lead to the potential to decrease the temperature, and vice versa (Chapin et al.
2005
). Lower land surface albedo indicates lower reflectivity and higher shortwave
absorption of the land surface. Taking forest coverage as an example, its albedo is
generally lower than that of the nudation and other vegetation types (Houldcroft
et al.
2009
). Historical deforestation in the middle-latitude zone led to the increase
of the land surface albedo, which is especially remarkable after snowfall in the
winter, and might have made northern hemisphere colder (Feddema et al.
2005
).
Leaf area index is an important indicator that represents the canopy structure and
productivity of the plant community. It directly influences the ability of plant to acquire
and utilize solar energy and indirectly influence the canopy impedance ratio. Besides,
being an important parameter of land surface albedo, it also directly influences the
interaction between land surface and the atmosphere (Bonan and Pollard
1992
). More
recent studies have focused on the role of the leaf area index in influencing the climate.
The relevant researches indicate that leaf area index is closely related with precipita-
tion, temperature and specific humidity, etc. (Copeland et al.
1996
).
The significance of roughness has also been well realized. Land surface
roughness has impacts on the turbulent flow between land surface and the atmo-
sphere and subsequently influences the local diffusion flux. If diffusion flux is
higher, it will reduce the near-surface air temperature under the condition of no
other feedback mechanisms (Bathiany et al.
2010
). Deforestation will decrease
land surface roughness and reduce the turbulent flow, and will consequently
increase the temperature in theory. However, less turbulent flow will lead to the
decrease of heat and moisture transfer, which will increase the temperature and
moisture gradients between land surface and the atmosphere and in turn alleviate
the warming effect. Davin and Noblet-Ducoudré (
2010
) analyzed the sensitivity to
the roughness during the conversion of the forest to the grassland. Their result
indicates that the change in roughness will make global temperature increase by
0.29 C, and the increase will be even more obvious in the tropic zone.
