Examining the impact of land cover change for biofuel production on the Midwestern U.S. hydroclimate using a regional climate model.

Abstract:

The perennial grasses miscanthus (Miscanthus x giganteus) and switchgrass (Panicum virgatum) have been proposed as cellulosic feedstocks for U.S. biofuel production because their high productivity and low inputs could reduce net CO₂ emissions. Possible biogeochemical feedbacks of widespread production have been extensively studied, but less attention has been given to the two-way biophysical interactions between the land surface and regional climate. Miscanthus uses significantly more water than maize, resulting in large evapotranspiration (ET) increases upon conversion from maize to Miscanthus that could impact regional precipitation, precipitation recycling, and soil moisture. In this study, we simulate perennial grass production in a fully coupled regional climate model with dynamic vegetation, enabling an investigation into the two-way responses between these potential biofuels and the climate over the Mississippi River Basin. We incorporated algorithms of miscanthus and switchgrass growth and management from the Agro-IBIS model into with WRF-CLM4crop, a version of the Weather Research and Forecasting model coupled to the Community Land Model with dynamic crop growth and irrigation enabled. Using suggested production regions from the United States Department of Energy, we performed simulations driven with 10 years of NCEP-DOE Reanalysis (NCEP2) data, with 25%, 50%, and 75% of current croplands replaced by perennial grass feedstocks. Our results provide spatially explicit maps of how simulated ET increased with conversion and the resulting regional cooling, greater precipitation, and precipitation recycling over the region.