近50年新疆温度降水配置演变及其尺度特征

MULTI-SCALE FEATURE OF CLIMATE AND CLIMATE SHIFT IN XINJIANG OVER THE PAST 50 YEARS

中文关键词:  正交小波，全球增暖，新疆气候，高温多雨，多尺度特征。

英文关键词:Orthogonal wavelets, Global warming, Xinjiang, Warm-rainy climate, Multi-scale analysis.

中文摘要:

      用小波多分辨分析方法研究近20年新疆出现的高温多雨型气候的时间尺度特征及其演变趋势。新疆近55年温度和降水的小波功率谱分析显示，二者在年际尺度上都有2—4和6—8 a的显著周期分量，在年代际尺度上有准16 a周期；但它们的时间演变和时间平均谱都存在差异，导致温度和降水配置演变比较复杂，呈现非平稳性。正交小波分解证实，温度和降水年际变化的高频部分具有显著的负相关，除个别几年外几乎都是高温少雨或低温多雨配置；在年际变化的低频部分，即6—8 a尺度部分，高温少雨/低温多雨及高温多雨/低温少雨配置交替出现，55 a平均而言二者相关性不显著。在年代际以上尺度，二者的能量主要集中在约50 a以上尺度部分，16—32 a尺度部分方差贡献很小。在降水和温度时间序列中去除趋势后发现，50 a以上尺度部分具有稳定的高温多雨/低温少雨配置。因此，近20年新疆高温多雨型气候的出现主要是二者50—60 a尺度成分的正位相和线性增加趋势部分叠加形成的，其中降水主要是年代际尺度成分的贡献，温度主要是线性增暖趋势即全球变暖的影响结果。

英文摘要:

      The scale feature of the Xinjiang climate change associated with the recent 20- year warm-wet climate is studied by wavelet decomposition. One of regional characteristics in climatology is the collocation of temperature and rainfall. There are four types of collocations i.e. warm-wet, cool-dry, warm-dry and cool-wet climates. As well known, a rainy climate does not represent a wet climate sometimes due to surface evaporation change. For example, if the increase rate excess the precipitation the climate would become drier. For avoiding miss-understanding, the words warm-rainy or cool-rainy are used in following content of this paper. Xinjiang is a Uygur autonomous region in northwestern China with a very dry continent climate. The water resource is one of the most important factors for regional economic development. In contrary to the severe drought occurred in north China during the past 30-year, the rainfall in Xinjiang has apparently increased since mid-1980s accompanying a warm climate under the background of global warming. Some of scientific researches conjecture that a climate transition from warm-dry to warm-rainy has occurred in mid-1980s. This change has led to more rainfall and warm climate there, mountain glacial shrinkage, runoff augment, lake expansion, frequent floods and so on. The surface vegetation has been ameliorated significantly according to remote sensing from satellite. The rainfall wavelet power spectrum shows 2-4-years /and 6-8-years periods at inter-annual variation belt, and about 16-year period at inter-decadal scale. The different spectra of the temperature and rainfall sequences imply a complex collocation with their evolutions. In addition to continuous wavelet analysis the temperature and rainfall sequences are also decomposed with orthogonal wavelets Daub4 for reducing the edge-effect. It shows a significantly negative correlation between them at high frequency belt and a weak correlation in low frequencies within inter-annual variation belt, resulting from their non-stationary properties. A further quantitative investigation shows that the major precipitation energy concentrates on inter-annual variation and the part beyond 50-year components, as well, while the trend is the dominant component in temperature decomposition. The temperature and rainfall components exhibit a significant correlation, i.e. a warm-rainy/cool-dry climate collocation for the components. A further analysis has revealed that the appearance of the Xinjiang warm-rainy climate is contributed by the positive phase of 50-60-year component in precipitation and the warm trend during the recent 20-year. The persistence of the warm-rainy climate in Xinjiang seems expected in near future if global warming keeps on going. Finally, uncertainties for such a simple estimate to future climate of Xinjiang is discussed with the consideration of sea-ice interaction over west Europe and the Atlantic.