NOAA/WDS Paleoclimatology - Wilson - St. Emmeram Church (roof frame) Regensburg - ABAL - ITRDB GERM072

This paper presents a 500 year March-August precipitation reconstruction for the Bavarian Forest region of southeast Germany based on a composite, well-replicated data set of 676 living and historical tree-ring width series from Norway spruce. Two versions of the chronology are developed. The cubic smoothing spline (SPL) chronology, standardized with a fixed 80 year spline function, retains decadal and higher frequency variation. The regional curve standardization (RCS) chronology uses regional curve standardization to retain additional lower frequency variation from the same data. Calibration (1879-1978) of these chronologies with March-August precipitation indicates they explain 40% (SPL) and 34% (RCS) of the variability in the instrumental precipitation record. The SPL reconstruction models the high frequency variation better, whereas the RCS reconstruction tracks the low-frequency trends more robustly. It suggests that spring-summer precipitation was above the long-term average for the periods 1730-1810 and 1870-2000, about average between 1560 and 1610 and that significantly drier periods occurred during 1510-60, 1610-35, 1660-1730 and 1830-70. The low-frequency trends of the RCS reconstruction during the 19th century were verified by comparison with a regional precipitation series derived from 14 long precipitation records from central Europe. Better verification results were obtained using the original (non-homogenized) records over this interval. These results suggest that some low-frequency variability may have been removed during correction of these early records. Periods of synchronous decadal variability were observed between the SPL series and independent dendroclimatic reconstructions from central Europe. The RCS reconstruction is the first dendroclimatic precipitation reconstruction in Europe to capture low-frequency information. These long-term trends, however, are difficult to verify owing to the paucity of other proxy precipitation records in central Europe that portray low-frequency information. Further verification and testing of the RCS reconstruction will require the development of additional reconstructions from tree-rings (or other proxy data series) that similarly target low-frequency variability.

本研究基于由676条挪威云杉活体与历史树木年轮宽度序列构建的复合、高重现数据集，为德国东南部巴伐利亚林地区域重建了500年的3-8月降水序列。本研究构建了两种年表版本：采用固定80年样条函数进行标准化的三次平滑样条（cubic smoothing spline，SPL）年表，可保留年代际及更高频率的降水变率；而区域曲线标准化（regional curve standardization，RCS）年表则通过区域曲线标准化方法，从同一数据集内保留额外的低频变率。以1879-1978年的3-8月器测降水数据对两种年表进行校准，结果显示SPL年表与RCS年表可分别解释器测降水记录中40%和34%的变异性。SPL重建序列能更好地拟合高频变率，而RCS重建序列则更稳健地追踪低频变化趋势。分析结果表明：1730-1810年与1870-2000年时段的春夏季降水高于长期平均水平，1560-1610年时段降水接近长期均值；1510-1560、1610-1635、1660-1730及1830-1870年则为显著偏干时段。研究通过与中欧14条长序列降水记录构建的区域降水序列对比，验证了RCS重建序列在19世纪的低频变化趋势。在此时段内，采用原始（未均一化）记录可获得更优的验证结果，这表明早期器测降水记录在均一化校正过程中可能移除了部分低频变率。SPL序列与中欧其他独立树轮气候重建序列之间存在同步的年代际变率特征。RCS重建序列是欧洲首个可捕捉低频变率信息的树轮气候降水重建序列。然而，由于中欧地区缺乏其他可反映低频变率的代用降水记录，这类长期趋势难以得到验证。未来若要对RCS重建序列开展进一步验证与测试，需构建更多以捕捉低频变率为目标的树轮（或其他代用资料序列）重建序列。