Investigating the Impact of Land Cover Change on the Northern Great Plains

Over the Northern Great Plains (NGP, North/South Dakota and Western Minnesota) there has been a transition from grains to leafier crops due to a warming climate, genetically modified hybrids and the economy. From 2006-2011 in North Dakota soybean and corn acres increased by almost 700,000 acres (about the size of Rhode Island) and the trend continues. The expansion of this crop belt plays an important role in the regional weather and climate through evapotranspiration. As a result, land-surface interactions and thus the Land Surface Model (LSM) of a regional climate model must be carefully considered. With an end goal of diagnosing the impacts changing land cover have on the boundary layer in the NGP including influences on convection and precipitation, this study has two goals. First, the sensitivity of LSM selection is explored in regional climate simulations using the Weather Research and Forecasting (WRF) model. LSMs evaluated will include Noah-MP with and without dynamic vegetation, and a version with a dynamic crop model (Noah-MP-Crop). In the latter case, methods are described to tune the model to the region. In absence of in-situ observations of Leaf Area Index (LAI), satellite derived LAI from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor are used. This data is collocated with the Cropland Data Layer (CDL) produced by the United State Dept. of Agriculture (USDA) to provide confidence in LAI isolated to specific crops, necessary for the tables needed by Noah-MP-Crop. This exercise demonstrates that there is significant year-to-year variability in LAI suggesting that dynamic vegetation is necessary to properly model land-surface interactions over the NGP.