Biogeophysical consequences of a tropical deforestation scenario: A GCM simulation study

Journal Article · Sun Dec 01 04:00:00 EST 1996 · Journal of Climate

DOI:https://doi.org/10.1175/1520-0442(1996)009<3225:BCOATD>2.0.CO;2· OSTI ID:447198

Sud, Y C; Lau, W K.M.; Walker, G K ^[1]

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1. NASA/Goddard Space Flight Center, Greenbelt, MD (United States); and others

Two 3-year (1979-1982) integrations were carried out with a version of the GLA GCM that contains the Simple Biosphere Model (SiB) for simulating land-atmosphere interactions. The control case used the usual SiB vegetation cover (comprising 12 vegetation types), while its twin, the deforestation case, imposed a scenario in which all tropical rainforests were entirely replaced by grassland. Except for this difference, all other initial and prescribed boundary conditions were kept identical in both integrations. An intercomparison of the integrations shows that tropical: deforestation decreases evapotranspiration and increases land surface outgoing longwave radiation and sensible heat flux, thereby warming and drying the planetary boundary layer. This happens despite the reduced absorption of solar radiation due to higher surface albedo of the deforested land. Produces significant and robust local as well as global climate changes. The local effect includes significant changes (mostly reductions) in precipitation and diabatic heating, while the large-scale effect is to weaken the Hadley circulation but invigorate the southern Ferrel cell, drawing larger air mass from the indirect polar cells. Decreases the surface stress (drag force) owing to reduced surface roughness of deforested land, which in turn intensifies winds in the planetary boundary layer, thereby affecting the dynamic structure of moisture convergence. The simulated surface winds are about 70% stronger and are accompanied by significant changes in the power spectrum of the annual cycle of surface and PBL winds and precipitation. Our results broadly confirm several findings of recent tropical deforestation simulation experiments. In addition, some global-scale climatic influences of deforestation not identified in earlier studies are delineated. 57 refs., 10 figs., 3 tabs.

• OSTI ID: 447198
• Journal Information: Journal of Climate, Journal Name: Journal of Climate Journal Issue: 12 Vol. 9; ISSN 0894-8755; ISSN JLCLEL
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ALBEDO
BIOSPHERE
BOUNDARY CONDITIONS
CLIMATIC CHANGE
DEFORESTATION
ENVIRONMENTAL EFFECTS
GENERAL CIRCULATION MODELS
HEAT FLUX
MOISTURE
RANGELANDS
TERRESTRIAL ECOSYSTEMS