Synoptic Scale Atmospheric Circulation and Summer Drought Variability of the Past Three Centuries, Boreal Canada

• Author(s) / Creator(s)

  • Tardif, J.C.
  • Girardin, M.P.
  • Flannigan, M.
  • Bergeron, Y.

• Five independent multicentury reconstructions of the July Canadian Drought Code and one reconstruction of the mean July-August temperature were developed using a network of 120 well-replicated tree-ring chronologies covering the area of the eastern Boreal Plains to the eastern Boreal Shield of Canada. The reconstructions were performed using 54 time-varying reconstruction submodels that explained up to 50% of the regional drought variance during the period of 1919-84. Spatial correlation fields on the six reconstructions revealed that the meridional component of the climate system from central to eastern Canada increased since the mid-nineteenth century. The most obvious change was observed in the decadal scale of variability. Using 500-hPa geopotential height and wind composites, this zonal to meridional transition was interpreted as a response to an amplification of long waves flowing over the eastern North Pacific into boreal Canada, from approximately 1851 to 1940. Composites with NOAA Extended Reconstructed SSTs indicated a coupling between the meridional component and tropical and North Pacific SST for a period covering at least the past 150 yr, supporting previous findings of a summertime global ocean-atmosphere-land surface coupling. This change in the global atmospheric circulation could be a key element toward understanding the observed temporal changes in the Canadian boreal forest fire regimes over the past 150 yr.

• Date created

  2006

• Subjects / Keywords

  • North pacific
  • Dendroclimatic reconstruction
  • Southern-oscillation
  • Sea-surface temperatures
  • Fire frequency
  • El-nino
  • Tree-rings
  • Pacific decadal variability
  • Extended dry spells
  • Interdecadal variability

• Type of Item

  Article (Published)

• DOI

  https://doi.org/10.7939/R3TM7215V

• License

  © 2006 American Meteorological Society. This version of this article is open access and can be downloaded and shared. The original author(s) and source must be cited.