Modelling the Tropical African Climate using a state-of-the-art coupled regional climate-vegetation model

In this study, three sixteen-year simulations were conducted to examine the influence of a new leaf area index (LAI) formula (derived from a modified version of the BIOME-BGC model) on the surface energy balance and surface climate of Tropical Africa using the Regional Climate Model version 4 (RegCM4) coupled with the Community Land Model version 4.5 (CLM45) including a module of carbon–nitrogen cycling (CN) (hereafter RegCM4-CLM45-CN). The first simulation considers the Satellite Phenology (SP) mode, the second one uses the old LAI formula and the third one uses the new LAI formula. The three simulations were designated as CLM45-SP, CLM45-CNold, and CLM45-CNnew respectively. The results showed that the simulated surface energy balance and surface climate are substantially affected by the new LAI formula. The CLM45-CNnew succeeds in reducing the high positive difference of LAI with respect to the CLM45-SP relative to the CLM45-CNold in some regions, although in other regions new differences appear. Also, the CLM45-CNnew is able to simulate the total evapotranspiration better than the CLM45-CNold in comparison with the reanalysis product and it shows a similar response relative to the CLM45-SP. Moreover, the CLM45-CNnew succeeds in reducing the cold bias relative to the CLM45-SP and CLM45-CNold against the observational dataset. For the total surface precipitation, the CLM45-CNnew shows a similar response to the CLM45-SP relative to the CLM45-CNold in comparison with the observational dataset. Overall, this study provides useful insights related to the advantage of the regional coupled RegCM4-CLM45-CNnew model and recommends its utilization for future studies on the potential roles/impacts of biosphere–atmosphere in modulating the climate of Tropical Africa.