Effects of vegetation feedback on future climate change over West Africa
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Abstract
This study investigates the impact of climate-vegetation interaction on future climate changes over West Africa using a regional climate model with synchronous coupling between climate and natural vegetation, the RegCM4.3.4-CLM-CN-DV. Based on the lateral boundary conditions supplied by MIROC-ESM and CESM under the greenhouse gas Representative Concentration Pathway 8.5, significant increase of vegetation density is projected over the southern part of Sahel, with an increase of leaf area index and a conversion from grass to woody plants around 7-10°N of Sahel. Regardless of whether the model treats vegetation as static or dynamic, it projects an increase of precipitation in eastern Sahel and decrease in the west. The feedback due to projected vegetation change tends to cause a wet signal, enhancing the projected increase or alleviate the decrease of precipitation in JJA in the areas of projected vegetation increase. Its impact is negligible in DJF. Vegetation feedback slightly enhances projected warming in most of West Africa during JJA, but has a significant cooling effect during DJF in regions of strong vegetation changes. Future changes of surface runoff are projected to follow the direction of precipitation changes. While dynamic vegetation feedback enhances the projected increase of soil water content in JJA, it has a drying effect in DJF. The magnitude of projected ET changes is reduced in JJA and increased in DJF due to vegetation dynamics. A high sensitivity of climate projection to dynamic vegetation feedback was found mainly in semiarid areas of West Africa, with little signal in the wet tropics
