湖南省近54年冬季降水分区及趋势分析

基于湖南省89个气象站点1960—2013年的冬季降水观测数据，应用旋转经验正交函数（REOF）和层次聚类法（HCA）对湖南省冬季降水进行分区，并在分区的基础上，运用离散小波变换结合Mann-Kendall（MK）和Sequential MK（SQMK）的方法，讨论湖南省各分区冬季降水的变化趋势，并识别影响各自变化趋势的主周期分量。结果表明:（1）REOF的前3个旋转空间模态揭示湖南省冬季降水存在3个主要的异常敏感区:湘南、湘西北及湘中；（2）湖南省冬季降水在空间上可划分为5个一致性子区域:湘西北区（DJF1）、湘西-湘北区（DJF2）、湘西南-湘中区（DJF3）、湘南丘陵区（DJF4）和湘南山地区（DJF5），且每一子区域从西南向东北呈带状展布；（3）近54年来，5个子区的冬季降水均表现出增加趋势但各区存在差异，其中，湘西南-湘中区、湘南丘陵区和湘南山地区均呈显著的上升趋势；（4）D₁分量是影响湖南省不同区域冬季降水变化趋势的最占优的周期分量，揭示湖南省的冬季降水变化趋势存在准2年的主周期。 

TREND ANALYSIS OF WINTER PRECIPITATION IN THE SUB-REGIONS OF HUNAN PROVINCE IN THE PAST 54 YEARS

In this study, the hierarchical clustering analysis (HCA) coupled with rotated empirical orthogonal functions (REOF) is applied to form sub-regions based on the winter precipitation data of 89 meteorological stations in Hunan Province during the period 1960-2013. Then, the method, combined with discrete wavelet transform, Mann-Kendall (MK) and sequential MK (SQMK), is used to analyze the trend of precipitation change and identify the most dominant periodic components that affect winter precipitation trends in each sub-region. The results are as follows. (1) The first three rotated EOF modes reveal three principal precipitation anomaly sensitive areas in Hunan Province: south Hunan, northwest Hunan and central Hunan. (2) Winter precipitation in Hunan can be divided into five homogeneous and distinct regions: northwest Hunan (DJF1), west Hunan - north Hunan (DJF2), southwest Hunan - central Hunan (DJF3), hilly areas of south Hunan (DJF4), and mountain areas of south Hunan (DJF5). And each of sub-regions is extended belt-like from southwest to northeast. (3) In the past 54 years, winter precipitation has an increasing trend in each of five sub-regions, but these trends are different from each other. The southwest Hunan - central Hunan, hilly areas of south Hunan and mountainous areas of south Hunan exhibit a statistically significant upward trend. (4) The wavelet component D1 is the most effective periodic components affecting the winter precipitation trends in the different regions of Hunan Province. It suggests that 2-year periodic events are the main driver behind the observed trend of precipitation in Hunan Province.