Impact of Deforestation on the Regional Climate over the Congo Basin
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Transcript of Impact of Deforestation on the Regional Climate over the Congo Basin
Impact of Deforestation on the Regional Climate over the Congo Basin
Wenxian ZhangSchool of Earth and Atmospheric Sciences
Georgia Institute of TechnologyApril 22, 2008
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Background
• Land and atmosphere interact in many aspects. Their interactions are important to regional climate.
• Regional climate are sensitive to land cover change, such as deforestation. Currently, deforestation is threatening the tropical forest in many countries.
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Background
• Due to the lack of direct observations and with the development of land models, modeling has become a primary approach to study land-atmosphere interaction.
• Numerous studies simulated the impact of deforestation on the regional climate in the Sahel, Amazon, and East Asia. Most of the results indicated a decrease in precipitation.
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Motivations
• To simulate a deforestation case in the Congo Basin
• To analyze the response of local climate to deforestation
- Hydrological cycle
- Surface energy balance
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Model Description
• A coupled run of the Community Land Model Version 3.3 (CLM3.3)
• A time period from 1979 to 1989; First Two years for spinning up
• Tow cases: control and modification
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Model Description
• Change the PFT from Broadleaf evergreen tropical trees to C3 grass
• Change the leaf area index (LAI) and the stem area index (SAI) according to the modification to the PFT
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Land States
• Increase
- Soil moisture
- Runoff
- Ground evaporation
- Albedo• Decrease
- Canopy Interception
- Transpiration
- Canopy evaporation
- LAI• Nearly the same
- Precipitation
- Evaporation
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Land States
• Increase
- Upward SW and LW
- Net SW and LW
- Bowen ratio
- Emissivity• Decrease
- Latent Heat• Slightly decrease
- Sensible heat
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Land States
• Increase
- Absorbed Infrared
radiation
- Sensible heat flux from
ground
- Ground temperature
- Surface wind• Decrease
- Photosynthesis
- Sensible heat flux from
vegetation• Slightly increase
- Absorbed solar
radiation
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Atmosphere States
• Slightly Increase
- High cloud cover
- Convective precipitation
- PBLH
- Surface air temperature• Decrease
- Low cloud cover
- Large-scale precipitation• Remain the same
- Precipitable water
- Planetary albedo
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Surface Water and Energy Budgets
Surface Water Budget Surface Energy Balance
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Ratios
• The ratios of transpiration
and canopy interception to precipitation are sensitive to deforestation.
• ET is the dominant component to balance precipitation.
• Latent heat flux is dominant in wet seasons.
• The trends of ratios for SH and LH are opposite
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Conclusions
• Deforestation causes an increase in soil water storage, a decrease in canopy interception and transpiration, and redistribution of evaporation.
• Precipitation and runoff do not show much difference.
• Deforestation leads to an increase in surface albedo, surface long-wave emissivity, and Bowen ratio.
• ET is the dominant term to balance precipitation; Latent heat flux is dominant to balance surface net radiation in wet seasons.