Impact of dynamic vegetation on near-surface meteorology using a newly developed WRF_NOAHMP_SUCROS coupled model

Abstract

The study attempts to quantitatively understand the impact of dynamic vegetation on land-surface atmosphere interactions over spring wheat croplands in India. A new modeling tool capable of simulating these interactions was developed by incorporating the crop growth module of the Simple and Universal Crop growth Simulator (SUCROS) crop model into the Weather Research and Forecasting (WRF) mesoscale model. An earlier study had calibrated and evaluated the stand-alone SUCROS crop model with observed data for spring wheat collected from an experimental site in northwestern India. The crop growth module of the calibrated SUCROS model was implemented in the Noah-MP land module of WRF to build the coupled WRF_NOAHMP_SUCROS model. Numerical experiments were conducted with WRF_SUCROS that simulates the simultaneous evolution of meteorological drivers and crop Leaf Area Index (LAI) and the two-way interactions between these processes. These experiments were compared with WRF simulations driven by observed climatological mean LAI. These experiments only simulate the effects of changes in LAI on meteorology but not the other round. Results show that the coupled WRF_NOAHMP_SUCROS model is able to simulate the LAI better than the default dynamic vegetation module in WRF. It also produces realistic simulations of the near-surface meteorological parameters. The latent heat flux (LHF) varies directly with LAI, and sensible heat flux (SHF) varies inversely with LAI. As the crop grows, the energy transfer occurs more in latent heat flux than sensible heat flux due to increased evapotranspiration. Hence the growing crops result in near-surface cooling due to decreased Bowed Ratio. The mixing ratio is also increased due to increased latent heat flux. The uncoupled WRF model also shows similar patterns except in the juvenile crop stage where it overestimates the sensible heating and temperature but underestimates latent heat fluxes and mixing ratio.