On the contribution of dynamic leaf area index in simulating the African climate using a regional climate model (RegCM4)

Abstract

To understand the contribution of dynamic leaf area index (LAI) in simulating the surface African climate, two 12-year simulations were analysed. The first simulation operates in the satellite phenology (SP) mode; meanwhile the second simulation relies on activating the carbon-nitrogen (CN) module. Both simulations used the variable infiltration capacity (VIC) as a land-surface hydrology scheme. The first simulation was referred to as SP-VIC, and the second one was designated as CN-VIC. The results showed that CN-VIC severely decrease LAI more than the SP-VIC particularly over the Congo basin. This leads to a severe decrease in vegetative evaporation and transpiration and a pronounced increase of soil evaporation in comparison with the SP-VIC. As a result, a remarkable decrease of total evapotranspiration was observed leading to a high warm bias relative to an observational dataset. The rate of total precipitation was less than when it is simulated by the SP-VIC, due to a decrease in the amount of water vapour transferred to the atmosphere. To ensure a superior performance of the coupled CN-VIC system, the four surface parameters of the VIC all need to be recalibrated over Africa particularly over the Congo basin, so the vegetation status and surface climate of Africa can be properly simulated.