赣江流域气象水文干旱传播特征分析

An Analysis of the Meteorological and Hydrological Drought Propagation Characteristics in Ganjiang River Basin

探究气象水文干旱传播规律对水文干旱的提前预警和减灾具有重要意义。基于赣江流域1960~2018年逐月降水量、气温和径流量资料,分别计算不同时间尺度上的标准化降水蒸散发指数(Standardized Precipitation Evapotranspiration Index,SPEI)、标准化降水指数(Standardized Precipitation Index,SPI)和标准化径流指数(Standardized Runoff Index,SRI),利用游程理论和Copula函数条件概率方法对比分析气象水文干旱特征及其干旱传播规律。结果表明:赣江流域年和季节尺度上的气象干旱与水文干旱变化过程相似,变化趋势一致,干旱指数反映流域春旱和冬旱呈现加重趋势,而夏旱和秋旱呈现减弱趋势,SPEI指数描述的夏旱强度要重于SPI和SRI指数,而反映的冬旱强度则弱于其他两种干旱指数;SPEI和SPI评估的赣江流域气象干旱事件分别为87和75次,SRI评估的水文干旱事件为65次,虽然气象干旱事件多于水文干旱,但水文干旱事件有着更长的历时和更高的烈度;干旱传播时间年内波动较大,雨季传播时间在1~2个月间,而在旱季干旱传播时间最长可达6个月,气温对干旱传播时间的影响在11月和12月最为明显;流域气象水文干旱的最优联合分布函数为Frank-Copula,气象干旱条件下,引发水文干旱事件的概率随着气象干旱加重而升高,同时气温影响下气象干旱引发水文干旱事件的阈值更高,并更倾向于引发烈度更强的水文干旱事件。研究结果有助于流域水文干旱事件的早期监测和预警。

Exploring the propagation pattern of meteorological and hydrological drought is important for early warning and disaster mitigation of hydrological drought.The standardized precipitation evapotranspiration index(SPEI),standardized precipitation index(SPI)and standardized runoff index(SRI)are calculated for different time scales based on the month-by-month precipitation,temperature and runoff data from 1960 to 2018 in the Ganjiang River basin,respectively.The characteristics of meteorological drought and hydrological drought are compared and analyzed by using operational theory and the Copula function conditional probability method,as well as the propagation pattern of meteorological drought to hydrological drought.The results show that the changing process of meteorological drought and hydrological drought in the Ganjiang River Basin on annual and seasonal scales is similar,and the changing trends show the same,and the drought index reflects that spring and winter droughts in the basin show an aggravating trend,while summer and autumn droughts show a weakening trend,and the summer drought intensity described by the SPEI index is heavier than that described by the SPI and SRI indices,while the winter drought intensity reflected by the SPEI index is weaker than that reflected by the other two drought indices.87 and 75 meteorological drought events assessed by SPEI and SPI,respectively,and 65 hydrological drought events assessed by SRI.Although there are more meteorological drought events than hydrological drought events,hydrological drought events have longer durations and higher intensities.Drought propagation time fluctuates greatly within the year,with propagation time between 1 and 2 months during the rainy season and up to 6 months during the dry season,and the effect of temperature on drought propagation time is most pronounced in November and December.The optimal joint distribution function of meteorological and hydrological drought is Frank-Copula,and the probability of triggering hydrological drought events under meteorological drought conditions increases with the worsening of meteorological drought,while meteorological drought under the influence of temperature is more difficult to trigger hydrological drought events,but more likely to trigger more severe hydrological drought events.The results of the study contribute to the early monitoring and warning of hydrological drought events in the basin.