湖南省近54年冬季降水分区及趋势分析

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

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。

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.