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Harvard Forest Symposium Abstract 2015

  • Title: Rainless day frequency variability across a subcontinental gradient of hydroclimate
  • Primary Author: Daniel Bishop (Harvard Forest)
  • Additional Authors: Neil Pederson (Harvard Forest)
  • Abstract:

    Extreme daily precipitation events have been, and are projected to continue to be, on the rise in the continental United States. Such changes are expected to increase the vulnerability of terrestrial ecosystems. Tree rings can provide a unique proxy of climate, offering a finer temporal scale for paleoclimate data, but they are limited in their resolution of extreme precipitation patterns and events over time. We used instrumental records to evaluate seasonal trends in rainless days across a moisture availability gradient in the contiguous eastern United States. We evaluated the relationship between rainless day frequencies to established hydroclimatic reconstructions to further characterize extreme events over the last 500-1000 years. From 1944-2013, we found that the northeast and midwest regions have been trending toward wetter summers and falls with fewer rainless days. Reconstructed PDSI exhibited a positive relationship with total summer rainfall and a negative relationship with rainless day frequency for all regions. We conclude that tree-ring drought reconstructions have a strong relationship with transient moisture conditions, especially in the Northeast region. More work will be needed to evaluate the possible synoptic-scale drivers of sub-seasonal precipitation trends and local-scale ecological effects of short-term dry periods. In addition, the ecological implications of daily precipitation under 1 mm remains unresolved, and warrants further research.

  • Research Category: Regional Studies