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Impact of Deforestation on the Regional Climate over the Congo Basin

Impact of Deforestation on the Regional Climate over the Congo Basin. Wenxian Zhang School of Earth and Atmospheric Sciences Georgia Institute of Technology April 22, 2008. Background. Land and atmosphere interact in many aspects. Their interactions are important to regional climate.

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Impact of Deforestation on the Regional Climate over the Congo Basin

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  1. Impact of Deforestation on the Regional Climate over the Congo Basin Wenxian Zhang School of Earth and Atmospheric Sciences Georgia Institute of Technology April 22, 2008

  2. 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.

  3. 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.

  4. Motivations • To simulate a deforestation case in the Congo Basin • To analyze the response of local climate to deforestation - Hydrological cycle - Surface energy balance

  5. 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 Model Description

  6. 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 Model Description

  7. Increase - Soil moisture - Runoff - Ground evaporation - Albedo Decrease - Canopy Interception - Transpiration - Canopy evaporation - LAI Nearly the same - Precipitation - Evaporation Land States

  8. Increase - Upward SW and LW - Net SW and LW - Bowen ratio - Emissivity Decrease - Latent Heat Slightly decrease - Sensible heat Land States

  9. 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 Land States

  10. 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 Atmosphere States

  11. Surface Water and Energy Budgets Surface Water Budget Surface Energy Balance

  12. 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 Ratios

  13. 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.

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