Potential impact of land use change on future regional climate in the Southeastern U . S . : 1 Reforestation and crop land conversion

17 The impact of future land use and land cover changes (LULCC) on regional and global 18 climate is one of the most challenging aspects of understanding anthropogenic climate change. 19 We study the impacts of LULCC on regional climate in the southeastern U.S. by 20 downscaling the NASA Goddard Institute for Space Studies (GISS) global climate model E to 21 the regional scale using a spectral nudging technique with the Weather Research and 22 Forecasting (WRF) Model. Climate-relevant meteorological fields are compared for two 23 southeastern U.S. LULCC scenarios to the current land use/cover for four seasons of the year 24 2050. In this work it is shown that reforestation of cropland in the southeastern U.S. tends to 25 warm surface air by up to 0.5 K while replacing forested land with cropland tends to cool the 26 surface air by 0.5 K. Processes leading to this response are investigated and sensitivity 27 analyses conducted. The sensitivity analysis shows that results are most sensitive to changes 28 in albedo and the stomatal resistance. Evaporative cooling of croplands also plays an 29 important role in regional climate. Implications of LULCC on air quality are discussed. 30 Summertime warming associated with reforestation of croplands could increase the 31 production of some secondary pollutants while a higher boundary layer will decrease pollutant 32 concentrations; wintertime warming may decrease emissions from biomass burning from 33 wood stoves. 34