1978-2017年西南地区干湿时空变化特征

Characteristics of Spatial-Temporal Variation of Dryness and Wetness from 1978 to 2017 in Southwestern China

利用1978—2017年91个气象站点1、3、6和12个月的标准化降水蒸散指数SPEI,采用极点对称模态分解ESMD、M-K突变检验和空间插值等方法,对西南地区的干湿时空变化特征进行分析。结果表明:(1)过去40 a里,西南地区呈干旱化趋势;ESMD分解的模态分量有年际振荡(2 a)和年代际振荡(10 a)特征,趋势分量呈波动性下降,2010年后未出现回升,表明干旱化程度在逐步加深。(2)综合ESMD和M-K突变检验得到2000年代初为干湿的突变时间。(3)西南地区干旱强度与湿润强度呈现负相关,大部分区域主要以干旱为主,其中四川西北部和贵州中东部干旱最严重,而四川南部湿润强度级别较高。(4)春季有极端干湿出现,夏季大部分地区以湿润为主,局部发生了极端干旱,秋冬两季发生了不同程度的干旱,局部出现湿润。

Based on SPEI of 91 meteorological stations with time scales of 1,3,6 and 12 months from 1978 to 2017 in southwestern China,the spatial-temporal variation characteristics of dryness and wetness were analyzed by means of ESMD,M-K mutation test and spatial interpolation methods.The results are as follows:(1)In the past 40 years,in the southwestern region it presented a trend of aridification.The mode components decomposed by ESMD had interannual oscillation(2 a)and interdecadal oscillation(10 a)feature and the trend components showed a fluctuating decline.There was no recovery after 2010 and drought degree was gradually deepening.(2)The ESMD and M-K mutation test were combined to obtain the dryness and wetness mutation time and it was in the early 2000s.(3)The drought intensity was negatively correlated with the wetness intensity,it was mainly drought in most regions.Extreme drought occurred in the northwest Sichuan and the central and eastern Guizhou,while the wet intensity in southern Sichuan was higher.(4)In terms of spatial distribution of seasonal average dryness and wetness intensity,extreme dryness and wetness appeared in spring,most of the areas were humid,and extreme drought occurred in some parts in summer.Drought occurred with different degrees in autumn and winter,and local humidity appeared in some areas.