The influence of two land-surface hydrology schemes on the terrestrial carbon cycle of Africa: A regional climate model study

Two 16-year simulations were conducted to study the influence of two runoff schemes [the default one is TOPMODEL (hereafter referred as TOP) and the other one is the variable infiltration capacity (VIC)] with vegetation is being interactive [by enabling the carbon–nitrogen (CN) module] on the terrestrial carbon cycle fluxes of Africa using the regional climate model—RegCM4. The first simulation was labelled as CN-TOP, while the second simulation was hereafter referred to as CN-VIC. The results were evaluated and compared against various observation-based satellites and reanalysis products. Results showed that the CN-TOP overestimates leaf area index (LAI) and slightly underestimates the terrestrial carbon fluxes in comparison with the reference product; meanwhile, the CN-VIC severely underestimates both LAI and terrestrial fluxes particularly over the Congo basin. In addition, the CN-VIC shows a superior performance for simulating the net ecosystem exchange (NEE) than when it is simulated by the CN-TOP. In summary, the coupled RegCM4-CLM45-CN-VIC model can be recommended for future studies of NEE over Africa. To obtain robust results for simulating the terrestrial carbon fluxes especially the NEE; it is highly recommended to calibrate the four parameters of the VIC surface data set over Africa particularly over the Congo basin against in-situ observations.