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Title: Tropical deforestation: Modeling local- to regional-scale climate change

Abstract

The authors report results from a model study using the National Center for Atmospheric Research Community Climate Model (Version 1) general circulation model to assess the impact of regional scale deforestation on climate change. In the model a large parcel in the Amazon basin is changed from tropical rain forest to scrub grassland. Impacts can include adding CO[sub 2] to the atmosphere by biomass burning, increasing surface albedo, changing precipitation and evaporation rates, impacting soil moisture, and general weather patterns. They compare their model results with earlier work which has looked at this same problem.

Authors:
; ;  [1];  [2];  [3];  [4]
  1. (Macquarie Univ., North Ryde (Australia))
  2. (Univ. of Arizona, Tucson (United States))
  3. (National Center for Atmospheric Research, Boulder, CO (United States))
  4. (Univ. of Technology, Sydney (Australia))
Publication Date:
OSTI Identifier:
6292769
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Geophysical Research; (United States); Journal Volume: 98:D4
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; DEFORESTATION; CLIMATIC CHANGE; GENERAL CIRCULATION MODELS; TROPICAL REGIONS; ALBEDO; BIOMASS; CARBON DIOXIDE; EVAPORATION; GREENHOUSE EFFECT; GREENHOUSE GASES; PRECIPITATION; RAIN; ATMOSPHERIC PRECIPITATIONS; CARBON COMPOUNDS; CARBON OXIDES; CHALCOGENIDES; ENERGY SOURCES; MATHEMATICAL MODELS; OXIDES; OXYGEN COMPOUNDS; PHASE TRANSFORMATIONS; RENEWABLE ENERGY SOURCES; SEPARATION PROCESSES 540210* -- Environment, Terrestrial-- Basic Studies-- (1990-); 540110

Citation Formats

Henderson-Sellers, A., Durbidge, T.B., Pitman, A.J., Dickinson, R.E., Kennedy, P.J., and McGuffie, K. Tropical deforestation: Modeling local- to regional-scale climate change. United States: N. p., 1993. Web. doi:10.1029/92JD02830.
Henderson-Sellers, A., Durbidge, T.B., Pitman, A.J., Dickinson, R.E., Kennedy, P.J., & McGuffie, K. Tropical deforestation: Modeling local- to regional-scale climate change. United States. doi:10.1029/92JD02830.
Henderson-Sellers, A., Durbidge, T.B., Pitman, A.J., Dickinson, R.E., Kennedy, P.J., and McGuffie, K. 1993. "Tropical deforestation: Modeling local- to regional-scale climate change". United States. doi:10.1029/92JD02830.
@article{osti_6292769,
title = {Tropical deforestation: Modeling local- to regional-scale climate change},
author = {Henderson-Sellers, A. and Durbidge, T.B. and Pitman, A.J. and Dickinson, R.E. and Kennedy, P.J. and McGuffie, K.},
abstractNote = {The authors report results from a model study using the National Center for Atmospheric Research Community Climate Model (Version 1) general circulation model to assess the impact of regional scale deforestation on climate change. In the model a large parcel in the Amazon basin is changed from tropical rain forest to scrub grassland. Impacts can include adding CO[sub 2] to the atmosphere by biomass burning, increasing surface albedo, changing precipitation and evaporation rates, impacting soil moisture, and general weather patterns. They compare their model results with earlier work which has looked at this same problem.},
doi = {10.1029/92JD02830},
journal = {Journal of Geophysical Research; (United States)},
number = ,
volume = 98:D4,
place = {United States},
year = 1993,
month = 4
}
  • The potential impacts of deforestation in the humid Tropics are examined using a version of the National Center for Atmospheric Research`s CCM1 coupled with the Biosphere-Atmosphere Transfer Scheme package. Tropical deforestation in South America, Africa, and Southeast Asia is studied using the results from an 11-yr deforestation experiment and a 25-yr control integration. It is found that the local-scale impact (here defined as within the area deforested) varies greatly between the three deforested regions due to the differing controls on the local atmospheric circulation: the Southeast Asian monsoon is much less sensitive to deforestation than the low-level flow over Southmore » America. The analysis of the changes in cloud radiative forcing suggests that reduction in cloud amount can significantly mitigate the imposed increases in surface albedo. The importance of water recycling by the forest canopy is stressed in the simulation of local precipitation changes. Correlation analysis of the changes resulting from the deforestation has been used to determine the nature of the processes that follow from the removal of the forest canopy and to suggest the important processes. The role of large-scale dynamics is explored in a companion paper. 44 refs., 9 figs., 5 tabs.« less
  • An atmospheric general circulation model with land surface properties represented by the simplified Simple Biosphere model is used to investigate the effects on local climate due to tropical deforestation for the Amazon basin. One control and three anomaly integrations of 4 years` duration are performed. In the anomaly integrations, rain forest in South America is replaced by degraded grassland. The anomaly integrations differ only in the optical properties of the grassland vegetation, with net surface albedos ranging from the same as to 0.09 lighter than that of rain forest. It is found that the change in climate, particularly rainfall, ismore » strongly dependent on the change in surface albedo that accompanies deforestation. Replacement of forest by grass causes a reduction in transpiration and reduces frictional convergence by decreasing surface roughness. However, precipitation averaged over the deforested area is not necessarily reduced. Average precipitation decreases when the increase in albedo is greater than 0.03. If surface albedo is not increased appreciably as a result of deforestation, moisture flux convergence driven by the increase in surface temperature can offset the other effects, and average precipitation increases. As albedo is increased, surface temperature does not change, but surface latent and sensible heat flux decreases due to reduced radiational energy absorbed at the surface, resulting in a reduction in convection and precipitation. A change in the distribution of precipitation due to deforestation that appears to be independent of the albedo is observed.« less
  • This is the second in a pair of papers in which the possible impacts of tropical deforestation are examined using a version of the NCAR CCM1. The emphasis in this paper is on the influence of tropical deforestation on the large-scale climate system. This influence is explored through the examination of the regional moisture budget and through an analysis of the Hadley and Walker circulations. Modification of the model surface parameters to simulate tropical deforestation produces significant modifications of both Hadley and Walker circulations, which result in changes distant from the region of deforestation. A mechanism for propagation to middlemore » and high latitudes of disturbances arising form tropical deforestation is proposed based on Rossby wave propagation mechanisms. These mechanisms, which have also been associated with the extratropical influences of ENSO events, provide a pathway for the dispersion of the tropical disturbances to high latitudes. 27 refs., 20 figs., 1 tab.« less
  • A simulation of the climate response to Amazon deforestation has been carried out. Precipitation is decreased on the average by 25 percent or 1.4 mm/day, with ET and runoff both decreasing by 0.7 mm/day. Modifications of surface energy balance through change of albedo and roughness are complicated by cloud feedbacks. The initial decrease of the absorption of solar radiation by higher surface albedos is largely cancelled by a reduction in cloud cover, but consequent reduction in downward longwave has a substantial impact on surface energy balance. Smoke aerosols might have an effect comparable to deforestation during burning season. 8 refs.
  • The present study uses the general circulation model of the Laboratoire de Meteorologie Dynamique (LMD-GCM) coupled to the land-surface, vegetation model SECHIBA. The impact of deforestation on climate is discussed. Replacing tropical forests by degraded pastures changes albedo, the roughness length and the hydrological properties of the surface. The experiment was carried out over eleven years using the observed sea surface temperature from 1978 to 1988, which includes two major El Nino events. The discussion of the results in this study is limited to the regional impact of deforestation. The changes found for the surface fluxes in Amazonia, Africa, andmore » Indonesia are examined in detail and compared in order to understand the impact on temperature. Special attention is paid to feedback mechanisms which compensate for the surface changes and to the statistical significant of these results within athe tropical variability of climate. It is shown that the relatively small regional impact of deforestation in this study is statistically significant and largely independent of the El Nino-Southern Oscillation phenomenon. 27 refs., 7 figs., 11 tabs.« less