Li Baofu, Chen Zhongsheng, Yuan Xingzhong
College of Geography and Tourism, Qufu Normal University , Rizhao , China.
The Key Laboratory of Geographic Information Science, Ministry of Education, East China Normal University , Shanghai , China.
PeerJ. 2015 Oct 27;3:e1289. doi: 10.7717/peerj.1289. eCollection 2015.
Considerable attention has recently been devoted to the linear trend of drought at the decadal to inter-decadal time scale; however, the nonlinear variation of drought at multi-decadal scales and its relation to atmospheric circulation need to be further studied. The linear and nonlinear variations of the Palmer drought severity index (PDSI) in Shandong from 1900 to 2012 and its relations to the Pacific decadal oscillation (PDO), El Niño-Southern Oscillation (ENSO), Siberian high (SH) and Southern Oscillation (SO) phase changes from multi-scale are detected using linear regression, the Mann-Kendall test, ensemble empirical mode decomposition (EEMD) and the Pearson correlation analysis method. The results indicate that the PDSI shows no statistically significant linear change trend from 1900 to 2012; however, before (after) the late 1950s, PDSI shows a significant upward (downward) trend (P < 0.01) with a linear rate of 0.28/decade (-0.48/decade). From 1900 to 2012, the PDSI also exhibits a nonlinear variation trend at the inter-annual scale (quasi-3 and quasi-7-year), inter-decadal scale (quasi-14-year) and multi-decadal scale (quasi-46 and quasi-65-year). The variance contribution rate of components from the inter-annual scale is the largest, reaching 38.7%, and that from the inter-decadal scale and multi-decadal scale are 18.9% and 19.0%, respectively, indicating that the inter-annual change exerts a huge influence on the overall PDSI change. The results also imply that the effect of the four atmospheric circulations (PDO, ENSO, SH, SO) on PDSI at the multi-decadal variability scale are more important than that at the other scales. Consequently, we state that PDSI variation at the inter-annual scale has more instability, while that at the inter-decadal and multi-decadal scale is more strongly influenced by natural factors.
近年来，人们对年代际至年代际时间尺度上干旱的线性趋势给予了相当多的关注；然而，多年代际尺度上干旱的非线性变化及其与大气环流的关系仍有待进一步研究。利用线性回归、曼-肯德尔检验、集合经验模态分解（EEMD）和皮尔逊相关分析方法，检测了1900年至2012年山东帕尔默干旱严重指数（PDSI）的线性和非线性变化及其与太平洋年代际振荡（PDO）、厄尔尼诺-南方涛动（ENSO）、西伯利亚高压（SH）和南方涛动（SO）多尺度相位变化的关系。结果表明，1900年至2012年PDSI无统计学显著线性变化趋势；然而，在20世纪50年代后期之前（之后），PDSI呈显著上升（下降）趋势（P<0.01），线性变化率为0.28/十年（-0.48/十年）。1900年至2012年，PDSI在年际尺度（准3年和准7年）、年代际尺度（准14年）和多年代际尺度（准46年和准65年）上也呈现非线性变化趋势。年际尺度分量的方差贡献率最大，达到38.7%，年代际尺度和多年代际尺度的方差贡献率分别为18.9%和19.0%，表明年际变化对PDSI总体变化影响巨大。结果还表明，四个大气环流（PDO、ENSO、SH、SO）在多年代际变率尺度上对PDSI的影响比在其他尺度上更重要。因此，我们认为PDSI在年际尺度上的变化更不稳定，而在年代际和多年代际尺度上的变化受自然因素影响更强。
