Calculations of river-runoff in the GISS GCM: impact of a new
land-surface parameterization and runoff routing model of the Amazon River
Climate Dynamics 10 (1994) 6/7, 349-361, by F Abramopoulos:
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The study examines the impact of
a new land-surface parameterization and a river routing scheme on the hydrology
of the Amazon basin, as depicted by the NASA/Goddard Institute of Space Studies
(GISS) global climate model (GCM).
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The more physically realistic
land surface scheme introduces a vegetation canopy resistance and a six-layer
soil system. The new routing scheme allows runoff to travel from a river's
headwater to its mouth according to topography and other channel
characteristics and improves the timing of the peak flow.
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River runoff is examined near the
mouth of the Amazon and for all of its sub-basins. With the new land-surface
parameterization, river runoff increases significantly and is consistent with
that observed in most basins and at the mouth.
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One positive impact of the new
land-surface parameterization is that it produces more realistic evaporation
over the Amazon basin, which was too high in the previous version of the GCM.
The realistic depiction of evaporation also affects the thermal regime in the
lower atmosphere in the Amazon.
·
In fact, the lower evaporation in
some portions of the basin reduces the cloudiness, increases the solar
radiation reaching the ground, increases the net radiation at the surface, and
warms the surface as compared to observations. Further GCM improvement is
needed to obtain a better representation of rainfall processes.