Coupling the land surface model Noah-MP with the generic crop growth model Gecros: Model description, calibration and validation

Abstract

Interactions between vegetation and atmosphere have a large impact on weather and climate. During the last decade, enormous efforts have been made to improve the representation of vegetation dynamics in land surface models (LSM). The present study extends the LSM Noah-MP by the dynamic crop growth model Gecros that enables simulating the development of crop stands in a weather-driven manner. This extension is a pre-requisite to simulate two-way climate-crop interactions in climate projections. Based on a comprehensive five-year dataset on energy- and water fluxes, and soil water and crop data from two different climate regions of southwest Germany, we adapted the crop growth model Gecros, integrated it with Noah-MP, calibrated the coupled model for winter wheat and maize and tested its robustness in multiple-year validation runs against independent measurements. This sound data set yielded a robust parameterization that performed well both in calibration and in validation runs over in total 16 seasons. Due to pronounced differences in phenology among maize cultivars, wheat simulations were better than maize simulations. The simulated dynamics in leaf area index of wheat and maize differed largely from the one used in standard Noah-MP simulations. The new model yielded pronounced differences in the partitioning of evapotranspiration into transpiration and soil evaporation. The added value of the improved description of vegetation dynamics needs to be evaluated in high-resolution coupled crop-climate simulations in future.