The Implementation of a Carbon-Nitrogen Model into the Variable Infiltration Capacity (VIC) Model for Use in the Regional Arctic System Model (RASM)

The Regional Arctic System Model (RASM) is a coupled climate system model being developed by multiple institutions specifically for the Arctic region that includes the Weather Research and Forecasting (WRF) model as the atmospheric component, the Variable Infiltration Capacity (VIC) model as the land component, the Parallel Ocean Program (POP) model as the ocean component, and the Community Ice Code (CICE) as the sea ice component. Work is underway to include the Community Ice Sheet Model (CISM) to model ice sheets and to add a dynamic vegetation component to the land surface model. Within VIC, multiple vegetation types are allowed within a grid box, but vegetation characteristics are prescribed and are not allowed to vary interannually or in response to changes in the regional climate system. As a first step in the dynamic vegetation integration, we will present results from the implementation of a prognostic carbon-nitrogen model, the CN as used in the National Center for Atmospheric Research (NCAR) Community Land Model, into VIC for the simulation of biogeochemical cycles in RASM. In particular, we will evaluate how long it takes for the modeled carbon and nitrogen pools in VIC-CN to reach equilibrium in a spin-up run. Modeled vegetation characteristics such as leaf area index from offline VIC-CN simulations will be compared to those derived from satellites. Furthermore, we will show how surface evapotranspiration and energy balance in VIC-CN compares to that in the default VIC and in situ observations.