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The Climatic Effects of Deforestation in South and Southeast Asia
Abstract
Tropical deforestation alters the interactions between the land surface and the atmosphere which in turn has an impact on the regional climate. Deforestation in South Asia (Southern India and Sri Lanka) and Southeast Asia leads to warmer and drier climatic conditions. Simulations carried out using the Weather Research and Forecast Model (WRF) show that regional precipitation, evapotranspiration, latent heat flux and cloud cover all decrease in response to deforestation. Surface and ground temperatures as well as the sensible heat flux increase after deforestation. The response of atmospheric moisture convergence is specific to the region being considered and either enhances or modulates the changes in precipitation. Even when the atmospheric moisture convergence is strengthened, the reduction in evapotranspiration dominates thus producing less precipitation over the region. These changes are seen throughout the year including the Asian monsoon season and persist regardless of the strength of the monsoon. That means the climatic signal due to deforestation is decoupled from the monsoon circulation. The changes in precipitation and evaporation have a negative feedback on each other thus exacerbating the dry conditions. The primary changes due to deforestation, changes in evapotranspiration and surface albedo, have opposing impacts on the regional climate with the warming due to reduced evapotranspiration dominating over the cooling due to the increased surface albedo. In addition, the reduction in cloud cover partially offsets the reduction in the amount of shortwave radiation absorbed by the surface due to the higher surface albedo. The increased surface albedo under deforested conditions reduces the amount of energy available at the surface and by itself stabilizes the overlying atmosphere. But this stabilization largely depends on the extent of the deforested area and is only seen when the area of the deforested region is sufficiently large. Unlike in the case of deforestation, warming due to increased greenhouse gas forcing, which has larger magnitude compared to warming due to deforestation, intensifies both annual and summer monsoon precipitation over Sri Lanka.
Subject Area
Climate Change|South Asian Studies|Atmospheric sciences
Recommended Citation
Mawalagedara, Rachindra K, "The Climatic Effects of Deforestation in South and Southeast Asia" (2013). ETD collection for University of Nebraska-Lincoln. AAI3561381.
https://digitalcommons.unl.edu/dissertations/AAI3561381