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Dynamically Downscaled Projections of Phenological Changes across the Contiguous United States
Citation:
Mallard, M., K. Talgo, J. Bowden, AND T. Spero. Dynamically Downscaled Projections of Phenological Changes across the Contiguous United States. Community Modeling and Analysis System (CMAS) conference, Chapel Hill, North Carolina, October 26 - 30, 2020.
Impact/Purpose:
The presentation will inform the broader research community about projected changes to phenological indicators of spring onset and winter dormancy in plants within a dynamical downscaling framework.
Description:
Phenological indicators (PI), used to study the timing of plant and animal cycles in response to seasonal changes, can also be useful metrics to analyze the impact of climate change on agricultural systems and ecosystem services. Here, projected changes to the wintertime dormancy in plants (assessed using Chilling Units, or “CU”), onset of spring (expressed using the Extended Spring Index), and the frequency of hard freezes after spring onset (false springs) are examined within a regional climate modeling application using the Weather Research and Forecasting (WRF) model to downscale two global climate models to 36-km grid spacing. Over the contiguous U.S. (CONUS), both a historical (1995-2005) and future period (2025-2100) are simulated under Representative Concentration Pathways 4.5 and 8.5. Consistent with prior studies, spring onset is projected to occur earlier, with CONUS-average changes ranging between 12 to 36 days by the end of the century. False springs are projected to become more frequent in the complex terrain of the western CONUS while decreasing in frequency in regions of the eastern U.S. CU are found to decrease in the southern CONUS, which would negatively impact the productivity of deciduous fruit trees and other plants the following growing season, while portions of the western and northern CONUS experience increased CU. However, regional errors over the historical period in some of the PI used here exceed their projected end-of-century changes, indicating the need for improving simulated 2-m temperatures and the frequency with which they exceed certain thresholds that heavily influence these PI.
