前冬戴维斯海峡—巴芬湾区域海冰异常对中国东部春季极端降水频次的可能影响及预测价值

本文研究了前期冬季北极海冰与中国东部春季极端降水频次的联系及其可能机制,并进一步探讨了海冰异常信号对极端降水的预测价值。结果表明,前冬戴维斯海峡—巴芬湾区域海冰异常与中国东部春季极端降水频次经验正交分解第一模态(EOF1)之间存在密切联系。当前冬戴维斯海峡—巴芬湾区域海冰异常偏多时,冬季大气环流呈现出类北大西洋涛动(NAO)正位相的异常分布,并伴随经向的北大西洋三极型海温异常。该海温异常可以从冬季持续到春季,进而激发出从北大西洋到欧亚中纬度的纬向遥相关波列,在东亚地区引起气旋型环流异常。该气旋型环流异常会引起中国东部地区湿度显著增加,上升运动增强,从而为该地区极端降水的发生提供了有利的背景条件。相反,当前冬戴维斯海峡—巴芬湾区域海冰异常偏少时,其滞后引起的春季环流异常则不利于中国东部地区极端降水的发生。进一步的交叉检验结果表明,前冬戴维斯海峡—巴芬湾区域海冰异常信号对中国东部春季极端降水具有重要的预测价值。

Possible influence and predictive value of preceding winter sea ice anomalies in the Davis Strait-Baffin Bay for spring extreme precipitation frequency in eastern China

This study investigates the relationship between winter Arctic sea ice cover (SIC) and the frequency of spring extreme precipitation in eastern China and the underlying mechanisms. Furthermore, the predictive value of anomalous Arctic SIC signal for spring extreme precipitation in eastern China is explored. A close correlation is revealed between the first empirical orthogonal function mode (EOF1) of the spring extreme precipitation frequency and SIC anomalies in the Davis Strait-Baffin Bay (DSBB) in the preceding winter. In the North Atlantic, increasing in winter SIC anomaly is accompanied by anomalous winter atmospheric circulation that shows a positive North Atlantic Oscillation-like (NAO-like) distribution pattern, along with meridional tripolar sea surface temperature (SST) anomalies. North Atlantic SST anomalies can persist from the preceding winter to spring, further exciting a wave train from the North Atlantic to mid-latitude Eurasia and inducing cyclonic anomalies in East Asia. Such cyclonic anomalies can significantly increase humidity and upward air motion in eastern China, providing favorable conditions for extreme precipitation in the region. In contrast, decreasing in winter SIC anomaly causes delayed anomalous spring atmospheric circulation unfavorable for extreme precipitation in eastern China. Results of leave-one-out cross-validation further indicate that this anomalous SIC signal has positive predictive value for spring extreme precipitation in eastern China.