Incorporating the Role of Nitrogen in the Noah-MP Land Surface Model for Climate and Environmental Studies

Abstract:

Noah-MP (Niu et al., 2011; Yang et al., 2011) is the next generation land surface model for the Weather Research and Forecasting (WRF) meteorological model and the Climate Forecast Systems in the National Centers for Environmental Prediction. While Noah-MP does not currently contain a dynamic nitrogen cycle, this can readily be updated with the interactive vegetation canopy option. In this study, Noah-MP is coupled with the Fixation & Uptake of Nitrogen (FUN) model (Fisher et al., 2010) for the above ground processes and the soil nitrogen model from the Soil and Water Assessment Tool (SWAT) for the below ground processes. This combines FUN’s state-of-the-art concept of the carbon cost theory and SWAT’s strength in representing the anthropogenic effects on the nitrogen cycle. The processes employed from FUN are the nitrogen uptake and fixation of plants, both of which are directly linked to the plant productivity. If passive nitrogen uptake cannot meet the nitrogen demand, plants have to spend part of the photosynthesized carbon production on nitrogen acquisition. The processes employed from SWAT are nitrogen mineralization, nitrification, immobilization, volatilization, atmospheric deposition, and leaching. In addition, the modified universal soil loss equation is used to more accurately account for the nitrogen removal in sediment caused by surface runoff. Because human input of nitrogen greatly changes the nitrogen cycle, a simple nitrogen fertilization approach is also applied to crops. Preliminary results show that Noah-MP is capable of simulating the dynamics of the major nitrogen pools. Further comprehensive evaluation of the new model will be conducted at one or more experimental sites.