NOAA/WDS Paleoclimatology - Wilson - Seminargasse 8 Straubing Historical Timbers - ABAL - ITRDB GERM097

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.

本研究基于挪威云杉（Norway spruce）的676条活体与历史树木年轮宽度（tree-ring width）序列组成的复现性良好的合成数据集，重建了德国东南部巴伐利亚林区近500年3-8月的降水序列。本研究构建了两种年表版本：其一为三次平滑样条（cubic smoothing spline, SPL）年表，采用固定80年样条函数进行标准化处理，可保留年代际及更高频率的降水变率；其二为区域曲线标准化（regional curve standardization, RCS）年表，通过区域曲线标准化方法保留了同一数据集内更多的低频变率信息。以1879-1978年的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重建序列对高频变率的模拟效果更优，而RCS重建序列则更稳健地捕捉到了低频变化趋势。重建结果显示，1730-1810年与1870-2000年时段的春夏降水均高于长期平均水平，1560-1610年时段降水接近平均水平，而1510-1560年、1610-1635年、1660-1730年及1830-1870年则为显著偏干时段。通过与中欧14条长降水序列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。使用原始（未均一化）序列进行验证时，该时段获得了更优的验证结果，这表明早期器测降水记录的均一化校正过程可能移除了部分低频变率信息。SPL序列与中欧独立树轮气候重建（dendroclimatic reconstruction）序列之间，存在同步的年代际变率时段。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。但由于中欧地区可反映低频变率的代用降水记录较为匮乏，上述长期趋势难以得到有效验证。未来若要进一步验证与检验RCS重建序列，需开发更多以捕捉低频变率为目标的树轮（或其他代用数据序列）重建序列。