热带异常风场序列的傅立叶分析方案及试验

Fourier Analysis Scheme and Test of Tropical Anomalous Wind Fields

摘要:

给出了热带异常风场多年序列{V'(t)}的一个傅立叶分析方案。对热带(30°S~30°N)1月850 hPa等压面1948-2005年{V'(t)}的试分析表明:1){V'(t)}总模方S'中定常波异常{V'^*(t)}的模方S'^*远大于信风异常{[V'(t)]}的模方[S'],这与气候风场V模方S以信风为主的谱结构有显著差异。2){V'(t)}的谱结构具有低维、低阶的特征,|m|=0,6的13个低|m|分量共拟合了S'模方的87.2%。3)全域定常波异常的合成波模方S'_|m|^*随|m|增大递减,|m|=1、2的V'_|m|^*拟合了S'^*的44.4%,是构成{V'^*}的最主要的分量;φ纬定常波异常的累积模方拟合率P'_|m|^*(φ)存在纬际差异,赤道至10°S带是主要高值带,20°N及以北是另一个高值带。4)全域和φ纬度上t年定常波异常模方及|m|=1、2的分量模方和存在明显的年际变化,20世纪80年代以来它们的强异常与强ENSO事件密切相关。因此,傅立叶分析方法是研究热带异常风场时间序列时空结构的有效和有用的方法。

关键词:热带异常风场;傅立叶分析方案;1月850hPa异常风场;ENSO

Abstract:

This paper presents a Fourier analysis scheme on a sequence of monthly anomalous wind {V'(t)} in the tropical field. The analysis of tropical(30°S-30°N) {V'(t)} at 850 hPa in January from 1948 to 2005 shows that:1)Module square of steady wave abnormalities S'^* is much larger than that of the trade wind abnormalities[S']. It is significantly different from the spectral structure of module square S of climatological wind, which is mainly about the trade wind. 2){V'(t)} is characterized by low dimension and low order. The first 13 wave components(|m|=0, 6) fit 87.2% of {V'(t)} module square. 3)The module square of all-terrain abnormal steady wave S'_|m|^*decreases with the increase of|m|, and V'_|m|^*(|m|=1, 2) fit the 44.4% of S'^*, which is the most important component of {V'^*}. The accumulated module square fitting rate P'_|m|^*(φ) of abnormal steady wave varies with latitudes φ. The high value belt mainly lies from equator to 10°S and another locates in the region to the north of 20°N. 4)Module squares of {V'^*} in the entire domain and at φ latitude, and the sum of module squares of|m|=1, 2 have significant interannual variations;and they are closely related to the strong ENSO events since 1980s. Therefore, Fourier analysis method is very effective to study the spatial-temporal structure of the tropical anomalous wind fields.

Key words:tropical anomalous wind;Fourier analysis scheme;850 hPa anomalous wind field in January;ENSO