Land Surface Model CAS-LSM: Model Description and Evaluation

Comprehensive land surface models are very important for climate and weather forecasting and for improving our understanding of the relationships between humans and the Earth system. This work presents a land surface model of the Chinese Academy of Sciences (CAS-LSM) that considers groundwater lateral flow, human water regulation, soil freeze-thaw front dynamics, riverine dissolved inorganic nitrogen transport, anthropologic heat release, urban water usage, and urban planning based on the Community Land Model. Global simulations with the updated CAS-LSM were conducted to evaluate its performance, and the results show its advantages in reproducing ecohydrological processes. Groundwater lateral flow can replenish the groundwater depletion cone caused by overexploitation, where the offset rate increases as the aquifer thickness increases. The maximum thaw depth increases by 3.62 mm yr(-1) in permafrost areas, and the maximum frost depth decreases by 1.89 mm yr(-1) in seasonally frozen areas. Nitrogen fertilizer use and point-source pollution increase the riverine dissolved inorganic nitrogen flow rate in western Europe and eastern China. To further verify the model's ability to simulate the effects of urban planning implementation, simulations over Beijing were conducted using the Weather Research and Forecasting (WRF) model coupled with CAS-LSM. The results show that anthropogenic heat release enhances the sensible heat flux and temperature in the city center. In terms of urban water planning, most of the total water supply in Beijing should be used for urban irrigation, and a small part should be used for road sprinkling to obtain a greater cooling effect. Plain Language Summary This work presents a land surface model of the Chinese Academy of Sciences (CAS-LSM) that considers groundwater lateral flow, human water regulation, soil freeze-thaw front dynamics, riverine dissolved inorganic nitrogen transport, anthropologic heat release, urban water usage, and urban planning based on the Community Land Model. Global simulations with the updated CAS-LSM were conducted to evaluate its performance, and the results show its advantages in reproducing ecohydrological processes. Simulations conducted using the Weather Research and Forecasting (WRF) model coupled with CAS-LSM over Beijing show that the model can be used for urban water management. The results demonstrate that CAS-LSM is a feasible tool for studying the effects of human activities on land surface processes.