CR prepress abstract  -  doi: 10.3354/cr01450

The impact of climate change on the characteristics of the frost-free season over the contiguous United States as projected by the NARCCAP model ensembles

Shiyuan Zhong, Lejiang Yu, Julie A. Winkler, Ying Tang, Warren E. Heilman, Xindi Bian

*Email: zhongs@msu.edu

ABSTRACT: Understanding the impacts of climate change on frost-free seasons is key to designing effective adaptation strategies for ecosystem management and agricultural production This study examines the potential changes in the frost-free season length between historical (1971-2000) and future (2041-2070) periods over the contiguous U.S. with a focus on spatial variability and the uncertainties surrounding the projections using daily minimum temperature outputs from a six-member ensemble composed of three regional-climate models nested within three general-circulation models provided by the North American Regional Climate Change Assessment Program (NARCCAP). Despite broad agreement among ensemble members on future advance (delay) of last-spring (first-autumn) frost and thus an increase in the frost-free season length across the U.S., large inter-model spread, an indication of high uncertainties, exists especially over the mountainous West. The uncertainty surrounding the first-autumn frost is the major contributor to the high uncertainty in the projected frost-free season length for the West, in contrast to other regions, especially the Great Plains, where the ensemble spread in the last-spring frost contributes more to the season-length uncertainty. The lengthening is not symmetric in spring and autumn, and the asymmetry, which varies by region and model, is relatively small in the eastern and central U.S., and large in the western U.S. Across California and portions of the Southwest, the advance in the last-spring frost will be more than the delay in the first-autumn frost. Elsewhere in the western U.S., especially over high terrain, the frost-free season will lengthen more in autumn than spring.