基于树轮宽度的澜沧江源区干旱重建

Drought Reconstruction Based on Tree-Ring Width in Headwaters of the Lancang River

依据采自青海省杂多县昂赛乡的树轮样本,建立树轮宽度差值年表(RES)。相关普查表明,澜沧江源区6—7月平均的12个月时间尺度标准化降水蒸散指数(SPEI)与RES年表具有显著的正相关。利用RES年表重建了澜沧江源区1639—2013年6—7月平均的SPEI变化序列,重建方程方差解释量达到37. 4%,且经过交叉检验证明了方程的稳定性。重建序列展示了澜沧江源区干旱的长期变化情况,发现1694—1710、1753—1778、1830—1847、1862—1872、1892—1908、1919—1929、1978—1989年共7个偏湿阶段和1646—1673、1682—1693、1711—1731、1735—1752、1796—1809、1817—1829、1848—1861、1873—1886、1949—1959、1990—2000年10个偏干阶段。重建的SPEI序列存在30～64、19～21、4. 2～4. 3、2. 6～3. 2、2. 5 a和2. 2 a左右的显著变化周期。相关分析表明,赤道中东太平洋海温对澜沧江源区干湿变化具有显著影响。此外,澜沧江源区干湿变化可能与厄尔尼诺-南方涛动(EN-SO)、太平洋年代际振荡(PDO)、太阳活动等大尺度的气候驱动因子存在一定的联系。此次SPEI重建为澜沧江源区提供了长期干旱变化历史,可为该区水资源管理提供科学依据。

Tree-ring width residual chronology( RES) was developed from the tree-ring samples collected in Angsai Township,Zaduo County,Qinghai Province. The results of general survey showed that there was a high correlation between the tree-ring width chronology and the SPEI( June-July) at 12-month time scale. The June-July SPEI in the headwaters of the Lancang River was reconstructed from AD 1639 to 2013,and it was used to explain the 37. 4% of the total SPEI variance during their common period. The cross-validation revealed that the reconstructed equation was stable. The results showed that the relatively wet periods occurred during 1694-1710,1753-1778,1830-1847,1862-1872,1892-1908,1919-1929 and 1978-1989,and the relatively dry periods occurred during 1646-1673,1682-1693,1711-1731,1735-1752,1796-1809,1817-1829,1848-1861,1873-1886,1949-1959 and 1990-2000,respectively. The reconstructed SPEI series revealed that there were the significant variation periods of 30-64,19-21,4. 2-4. 3,2. 6-3. 2,2. 5 and 2. 2 years. Correlation analysis showed that the sea surface temperature in the middle-east equator Pacific Ocean affected significantly the dry-wet changes in the headwaters of the Lancang River. Our reconstruction was associated with the large-scale atmospheric-oceanic variability,such as the ElNio-Southern Oscillation( ENSO),Pacific Decadal Oscillation( PDO) and solar activity. This SPEI reconstruction could provide a long-term drought history in the headwaters of the Lancang River and serve as the scientific basis for water resources management in this semiarid region.