1979～2013年西北太平洋地区海平面气压场季节转换时间的变化分析

Analysis on the Variation of Seasonal Transition Time of the Northwest Pacific Sea Level Pressure during 1979-2003

采用1979~2013年NCEP/NCAR再分析资料,借助线性趋势、距平、累积距平、Mann-Kendall突变检验及Morlet小波等方法分析了西北太平洋地区海平面气压场季节转换时间的长期趋势和多尺度周期变化特征。结果表明:海平面气压场一年中存在两次季节转变,20°N^50°N海平面气压场冬夏季节转变的时间在第20候左右,而夏冬季节转变发生在第51候。并且海平面气压场的季节转换时间存在纬度差异与经度差异。通过趋势分析,发现海平面气压场由冬季型转变到夏季型的时间存在显著的趋势变化,并且在近35年内是趋于提前,其气候倾向率为-0.33候/10 a;夏季型转换为冬季型的时间趋于延后,气候倾向率为0.25候/10 a。季节转换时间的Mann-Kendall突变检测结果表明,海平面气压场由冬向夏的转换时间在1997~1998年间发生了突变;夏季型转换为冬季型的时间尚未发现显著突变。最后通过对季节转换时间的小波分析与小波功率谱的显著性检验得出,冬夏季节转换的时间具有显著的15 a周期变化;夏冬季节转换时间8 a周期振荡最为剧烈。

The linear trend analysis, Mann-Kendall test, and Morlet wavelet analysis methods are applied to analyze anomaly and cumulative anomaly of sea level pressure derived from the NCEP/NCAR reanalysis over the Northwest Pacific（20°N-50°N）. The seasonal transition time of sea level pressure over this region in the most recent 35 years（1979-2014） are revealed with a focus on its long time trend and periodic oscillation on multiple time scales. The results show that the sea level pressure experiences two seasonal transitions each year： The transition from winter status to summer status that takes place at about the 20 th pentad, and the transition from summer status to winter status that occurs at about the 51 th pentad. In addition, the seasonal transition time of the seal level pressure field varies with latitudes and longitudes. Using the trend analysis method, we find that the transition time of seal level pressure from winter status to summer status has significant interannual variability. In the most recent 35 years, the seasonal transition time from winter status to summer status trends to become early with a changing rate of about-0.33 pentad/10 a; the transition time from summer status to winter status has postponed by about 0.25 pentad/10 a. The result of Mann-Kendall test indicates that the transition time of sea level pressure from winter status to summer status experienced an abrupt change in 1997-1998, but there is no similar abrupt change in the transition time from summer status to winter status. Finally, using Morlet wavelet analysis and significance test for global wavelet power spectrum, we conclude that the transition time from winter status to summer status has a significant 15-years periodic oscillation and the transition time from summer status to winter status fluctuates primarily with an 8-year cycle.