强降水过程气候态季节内振荡及其在延伸期预报中的应用  

Climate Intraseasonal Oscillation of Heavy Rainfall Process and Its Application in Extend-Range Forecast

作　　者：梁萍[1] 丁一汇[2] 

机构地区：[1]上海市气候中心,上海200030 [2]中国气象局国家气候中心,北京100081

出　　处：《高原气象》2013年第5期1329-1338,共10页Plateau Meteorology

基　　金：国家自然科学基金项目(41205060);公益性行业(气象)科研专项(GYHY201006020;GYHY201306030);国家"973"项目(SQ2011CB046594)

摘　　要：10天以上低频振荡属季节内变化尺度，比高频天气扰动具有更长的可预报性，是开展延伸预报的重要途径。利用1960—2010年上海地区逐日降水观测和同期NCEP／NCAR再分析大气环流资料，采用非线性序列信号提取方法一经验模态分解（EEMD），首先分析了1960年以来上海地区强降水过程的气候态季节内振荡（CISO）特征，进一步考察其对强降水过程的预报效果，然后综合强降水过程CISO及其相联系的大气低频振荡进行强降水过程延伸预报改进试验。结果表明：（1）30天以上低频振荡演变的正、负位相阶段分别与汛期强降水过程的集中期和间歇期相一致。10～30天低频振荡分量除对汛期集中降水期的强降水过程起调制作用外，也是盛夏较强降水阶段性m现的重要原因。（2）就多年平均而言，基于强降水过程的CISO可预报出汛期e／3左右强降水过程的发生时段，是强降水过程延伸预报的重要依据。（3）上海地区强降水过程大多与其南、北侧大气环流lo～30天和30天以上准周期低频振荡的辐合相关，其中西太平洋副热带高压与北方系统的低频振荡对5天以上持续性降水过程的发生有重要作用。在CISO的基础上，结合大气环流低频振荡的辐合演变可进一步提高CIS（）对强降水过程的预报效果，是一种可参考应用的延伸预报方法。Low frequency oscillations （LFO） with periods over 10 d under intraseasonal scale are important means for extend-range forecast because of its relative longer predictability than synoptic scale perturba- tion with high frequency. In this paper, taking Shanghai as an example, using the daily rainfall observation in Shanghai and global NCEP/NCAR reanalysis atmospheric circulation data for the period of 1960--2010, climate intraseasonal oscillation （CISO） of heavy rainfall process （HRP） in Shanghai is firstly investigated by means of a new kind of nonlinear serial signal processing method named as EEMD （Ensemble Empirical Mode Decomposition）. And forecast effects on HRP basing on CISO are then evaluated. Finally, improve- ment experiments are tested by combining CISO of HRP and their relating LFO of atmospheric circula- tion. The results show that： （1） Positive （negative） phases of LFO with periods over 30d are consistent with active （break） periods of HRP during rainy season. While LFO with 10--30 d periods can not only modulate occurrences of HRP during the two active periods but also do contribution to severe rainfall stage during mid-summer. （2） 2/3 HRP occurrences during rainy season can usually be predicted basing on CI- SO of HRP, which may be an important clue for its extend-range forecast. （3） HRP in Shanghai usually is in close association with LFO convergences under both 10-- 30 d and over 30 d intraseasonal scale from both south and north directions. The LFO of west Pacific subtropical high and north systems exert impor- tant influences on continuous HRP lasting for more than 5 d. And the forecast effects can be improved by combining CISO of HRP and their relating LFO of atmospheric circulation, which may be a kind of means with certain value in practice of extend-range forecast.

关 键 词：季节内振荡 延伸预报 强降水过程 集合经验模态分解 

分 类 号：P456.3[天文地球—大气科学及气象学]