On the contribution of dynamic leaf area index in simulating the African climate using a regional climate model (RegCM4)
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ORIGINAL PAPER
On the contribution of dynamic leaf area index in simulating the African climate using a regional climate model (RegCM4) Samy A. Anwar 1 Received: 16 December 2018 / Accepted: 28 September 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
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.
1 Introduction The climate of Earth can be understood as a system of several interacting components and cycles (energy, water, biogeochemical) that link these components. Some components comprising the Earth system - include: the atmosphere, hydrosphere, cryosphere, biosphere, pedosphere and anthroposphere (Bonan 2016). Special focus is given to the hydrosphere, as the amount of water vapour in the air is regulated by the hydrological cycle between the atmosphere, ocean and land. The biosphere component is important as the vegetation controls the fluxes exchanged with the atmosphere which ultimately controls air temperature and total precipitation. In addition, the terrestrial vegetation controls the terrestrial hydrology cycle through regulation of evapotranspiration, infiltration, and runoff. In return the infiltration process controls the amount of water entering the soil. Soil water influences * Samy A. Anwar [email protected] 1
Egyptian Meteorological Authority, P.O. Box 11784, Qobry EL-Kobba, Cairo, Egypt
the vegetation cover status (in terms of LAI) through its effect on photosynthesis, and so also influences the surface energy balance (as represented by sensible and latent heat fluxes). Hydrological processes like infiltration, runoff and evapotranspiration, and biogeophysical feedbacks (such as changes in albedo, surface roughness, rooting depth, and canopy conductance), induced by changes in the vegetation cover, are all represented i
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