Piao Lin, Fu Zuntao, Yuan Naiming
Lab for Climate and Ocean-Atmosphere Studies, Dept. of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing, 100871, China.
Chinese Academy of Meteorological Science, Beijing, 100081, China.
Sci Rep. 2016 Jan 27;6:19958. doi: 10.1038/srep19958.
In this study, relations between winter-time Pacific-Northern America pattern (PNA)/East Pacific wave-train (EPW) and winter-time drought in the west United States over the period of 1951-2010 are analyzed. Considering traditional Pearson's Correlation Coefficient can be influenced by non-stationarity and nonlinearity, a recently proposed method, Detrended Partial-Cross-Correlation Analysis (DPCCA) is applied. With DPCCA, we analyzed the "intrinsic" correlations between PNA/EPW and the winter drought with possible effects of ENSO and PDO removed. We found, i) significant negative correlations between PNA/EPW and drought on time scales of 5-6 years after removing the effects of ENSO, ii) and significant negative correlations between PNA/EPW and drought on time scales of 15-25 years after removing the effects of PDO. By further studying the temporal evolutions of the "intrinsic" correlations, we found on time scales of 5-6 years, the "intrinsic" correlations between PNA/EPW and drought can vary severely with time, but for most time, the correlations are negative. While on interdecadal (15-25 years) time scales, after the effects of PDO removed, unlike the relations between PNA and drought, the "intrinsic" correlations between EPW and drought takes nearly homogeneous-sign over the whole period, indicating a better model can be designed by using EPW.
本研究分析了1951 - 2010年期间冬季太平洋 - 北美模式（PNA）/东太平洋波列（EPW）与美国西部冬季干旱之间的关系。考虑到传统的皮尔逊相关系数可能受到非平稳性和非线性的影响，应用了最近提出的一种方法——去趋势偏交叉相关分析（DPCCA）。通过DPCCA，我们分析了去除厄尔尼诺 - 南方涛动（ENSO）和太平洋年代际振荡（PDO）可能影响后PNA/EPW与冬季干旱之间的“内在”相关性。我们发现，i）去除ENSO影响后，在5 - 6年时间尺度上，PNA/EPW与干旱之间存在显著负相关；ii）去除PDO影响后，在15 - 25年时间尺度上，PNA/EPW与干旱之间存在显著负相关。通过进一步研究“内在”相关性的时间演变，我们发现在5 - 6年时间尺度上，PNA/EPW与干旱之间的“内在”相关性会随时间剧烈变化，但在大多数时间里，相关性为负。而在年代际（15 - 25年）时间尺度上，去除PDO影响后，与PNA和干旱之间的关系不同，EPW与干旱之间的“内在”相关性在整个时期几乎具有相同的符号，这表明使用EPW可以设计出更好的模型。
