“衡邵干旱走廊”历史降雨量时空特征及趋势分析

Spatial-temporal distribution pattern and trend analysis of rainfalls in the 'Heng Shao drought corridor'

采用"衡邵干旱走廊"28个气象站点建站以来的逐月降水资料,基于泰森多边形法、面积加权法得到该地区年、季、月尺度降雨量,应用Mann-Kendall(M-K)非参数检验、GIS空间分析及Hurst指数等研究了降水的时空特征及趋势,结合降水距平百分率指标(P_a)揭示气候异常特征.结果表明:时间上,"衡邵干旱走廊"年际降水呈弱增加趋势,无突变特征;年内降水集中,春季和夏季多,秋季和冬季较少,除了春季,其余季节降水均有突变;各站点年降雨量变化有增有减,仅武冈显著下降,M-K检验表明,有8个站点存在突变点.年尺度P_a显示,"衡邵干旱走廊"1994、2002年为中涝,2011年为中旱,其余绝大部分为正常年,且各站点雨涝重于旱情;从季、月尺度P_a来看,夏、秋季节干旱特征明显,秋季干旱强度高于夏季,且"伏旱"严重.空间上,"衡邵干旱走廊"降水高值区主要位于四周地势较高地区,低值区主要分布于盆地范围内;北部、东部降水呈增加趋势,中部、西部以减少趋势为主.Hurst指数揭示,"衡邵干旱走廊"降水未来趋势持续性略高于反持续性.

This study explores the spatial-temporal distribution and trend of rainfalls in the ＇Heng Shao drought corridor＇,based on the meteorological data of 28 weather stations in the area from 1951 to 2015.Rainfalls of the study area were obtained by analyzing monthly rainfall data using ＇Thiessen Polygon method＇in combination with＇area weighting factor method＇.Various statistical methods（e.g.,statistics and regression analysis,Mann-Kendall（M-K） non-parametric statistical test and Hurst exponent,etc.） were used to（1） determine spatial-temporal distribution pattern and trend of the rainfalls;（2） detect abrupt change within annual and seasonal components;and（3） interpret climate anomalies by combining precipitation percent departures.The results show that：（1）generally,annual rainfall in the study area displayed a slight increase,with an average rate of 2.035 mm/10 a and no feature indicative of significant change.The rainfall mainly occurred in March-August,and the total rainfall in spring,summer,autumn and winter was 498,448,230 and 194 mm,respectively.Additionally,abrupt change points were observed for all seasons except for spring.Meanwhile,the annual precipitation vary significantly between all the stations,i.e.only Wugang station shows a significant decrease in the annual precipitation,whereas eight stations display abrupt change points as shown by the Mann-Kendall model;（2）annual precipitation percent departures demonstrated that floods occurred in1994 and 2002,and drought happened in 2011.Also,drought was extremely severe in summer and autumn,especially in July and August,and thus was highly detrimental to the agricultural productivity;（3）geographically,annual rainfalls were more abundant in mountainous regions distributed in the outer parts of the study area while deficient in the＂Heng Shao basin＂.It is also noteworthy that rainfalls in the northern and eastern regions of the study area have been increasing with time,while decreasing in the central and western regions.Moreover,Hurst exponent reveals that：（1） rainfall will continue decreasing in Lengshuitan District,Nanyue District,Shuining County,Hengyang County,etc.,while increasing in Loudi City,Xinhua County,Lengshuijiang City,Hengdong County,Dongan County,etc.;and（2） the future trend of rainfall in Shuangfeng County,Liangyuan City,Leiyang City,etc.,will shift from increasing to decreasing,and vice versa in Shaodong County,Shaoyang County,Wugang City,Changning City,etc.