A regional high-frequency reconstruction of May-June precipitation in the north Aegean from oak tree rings, AD 1089-1989

摘要

May-June precipitation is the primary limiting factor in annual tree-ring growth of the oaks of northeastern Greece and northwestern Turkey (39-42 degrees N, 22-37 degrees E). In a regional tree-ring chronology of historic building and modern forest samples, the May-June precipitation explains at least 40% of the variance for 1900-1985, and is reconstructed here from A.D. 1089-1989. The reconstruction is compared to three other precipitation reconstructions for Turkey. The mean temperature of May and June is also a growth-limiting factor owing to its effect on the availability of precipitation to the trees, but is more difficult to calibrate and reconstruct accurately owing to the trees' indirect response and the low number of long-temperature records available for the interior of northwestern Turkey. An analysis of the various methods of manipulating oak tree-ring data for regional climate reconstruction shows that removing all but the high-frequency variability plus normalizing the oak data sets before combining them into a master chronology are optimal techniques for a reasonable precipitation reconstruction of the entire area over the instrumental period. However, these methods do remove the low-frequency signal and dampen some of the evidence of local extremes in May-June precipitation; these issues are discussed here and will be addressed in future research. (C) 2007 Royal Meteorological Society