A Multicentury Reconstruction of May Precipitation for the Mid-Atlantic Region Using Juniperus virginiana Tree Rings

Abstract

his paper presents a multicentury reconstruction of May precipitation (1200?1997) for the mid-Atlantic region of the United States. The reconstruction is based on the first principal component (PC1) of two millennial-length Juniperus virginiana L. (eastern red cedar) tree-ring chronologies collected from rocky, limestone sites in the Ridge and Valley province of West Virginia. A split-calibration linear regression model accounted for 27% of the adjusted variance in the instrumental record and was stable through time. The model was verified by the reduction of error (RE = 0.21) and coefficient of efficiency (CE = 0.20) statistics. Multidecadal changes in precipitation were common throughout the reconstruction, and wetter than median conditions and drier than median conditions occurred during the medieval climate anomaly (1200?1300) and the Little Ice Age (1550?1650), respectively. The full reconstruction contained evidence of interannual and decadal variability; however, the twentieth century recorded the greatest number of decadal extreme wet and dry periods. A comparison of the May precipitation reconstruction to other regional reconstructions [Potomac River, Maryland, streamflow (Cook and Jacoby); Virginia/North Carolina July Palmer hydrologic drought index (PHDI; Stahle et al.); Missouri July PHDI (Cleaveland and Stahle); and White River, Arkansas, streamflow (Cleaveland)] showed that the eastern U.S. decadal drought and pluvial events extended into the mid-Atlantic region. A positive correlation between PC1 and the winter North Atlantic Oscillation (NAO) index and comparisons of smoothed May precipitation and the NAO (Luterbacher et al.) indicated that J. virginiana?s response to May precipitation was mediated by winter temperature.