Investigating the effect of seasonal plant growth and development in 3-dimensional atmospheric simulations

The major question being examined in my dissertation is the effect of seasonal crop development and growth on the mesoscale heat, moisture, and momentum fluxes, and the atmospheric boundary layer. Daily plant growth and development functions are introduced to simulate the differences in atmosphere-biosphere heat, moisture, and momentum exchange resulting from the inclusion of seasonal plant growth and development into the Biosphere- Atmosphere Transfer Scheme (BATS) coupled to the National Center for Atmospheric Research Regional Climate Model (NCAR RegCM). Energy, moisture, and momentum fluxes are studied over a maize agroecosystem at the scale of an atmospheric grid cell. To incorporate daily plant growth and development into surface flux calculations, a physiological crop model (CERES v3.0) is used. CERES simulates daily plant growth and development as a function of both environmental conditions (temperature, precipitation, solar radiation, and soil moisture) and plant-specific genetic parameters. The BATS and CERES models at first were driven by the observed weather data collected by the Automated Weather Data Network (AWDN) stations operated by the University of Nebraska, and selected crop parameters (i.e., Leaf Area Index [LAI], canopy height) were validated against field data. Growth and development functions from CERES were incorporated into BATS and the sensitivity of sensible and latent heat fluxes, and momentum flux to plant growth was quantified. Coupled RegCM/BATS simulations were then performed over the conterminous United States domain at a spatial resolution of 90 x 90 km to investigate the effect of interactively-simulated Leaf Area Index (LAI) and canopy height on mesoscale atmospheric circulations over the central Great Plains of North America. This study suggested that during the extremely dry season of 1988, 20–35% changes in sensible heat and 3–045% changes in latent heat occurred in response to LAI changes from 5 to 1 (the values simulated in the control and realistic experiments respectively). Two to four °C changes in surface and air temperatures resulted in response to such changes in surface fluxes; and mixing ratio and lower atmospheric winds were affected as well. This effect had a distinct diurnal pattern, with the strongest signal seen in mid-afternoon hours, and was more pronounced during the dry 1988 rather than the relatively normal 1991 growing season