中国云南小江流域泥石流暴发与ENSO的关联性

摘要

选取典型泥石流发育区云南小江流域为研究对象,利用典型泥石流沟滇北小江流域蒋家沟的长期观测资料,分析了小江流域泥石流暴发与该流域邻近的沾益及会泽常规气象站夏季(6-8月)降水的关系,以及小江流域及其周边地区夏季降水与ENSO的关系.结果表明,蒋家沟泥石流暴发的次数与夏季降水量有显著的正相关关系,而夏季降水和前期的Nino3区海表温度(SST)呈显著的负相关;每年泥石流发生的次数与首场泥石流发生的早晚关系密切,而激发首场泥石流的降水量与冬春Nino3区SST呈负相关；泥石流暴发次数与大雨日数关系密切,而大雨日数与Nino3区SST具有较好的对应关系.这说明冬春季Nino3区SST对小江流域泥石流的暴发次数有显著的影响,形成了ENSO与小江流域及蒋家沟泥石流发生的关联性.分析结果亦表明,Nino3区1月SST与当年蒋家沟泥石流次数具有显著的负相关关系,El Ni(n)o位相年泥石流少发而La Ni(n)a位相年泥石流多发.Nino3区SST变化最少要超前泥石流暴发4个月,因而ENSO可以为云南北部泥石流的预测预报提供一种指标信息,从而有可能利用ENSO冬季信息来预测小江流域及其周边地区(滇北)当年夏季泥石流活动.%Using a long-term observation dataset of typical debris flows in Jiangjiagou ravine in Xiaojiang River basin, northern Yunnan Province, this paper analyzes the relationship between debris flows and rainfall as well as that between ENSO and JJA (June, July, August) precipitation of Zhanyi and Huize regular meteorological stations in the vicinity of Jiangjiagou ravine. The results show that the number of the debris-flow occurrences in Jiangjiagou Ravine are positively related to the JJA rainfall, which is significantly negatively related to the January SST in Nino3 region. Moreover, the annual number of debris flows strongly depends on the date of the first occurrence in that year, while the precipitation of May and June which triggers the first occurrence is negatively related to the Nino3 SST in winter and spring. The debris flow in Jiangjiagou is sensitive to the heavy rainfall (>25 mm) that responds well to the Nino3 SST. This suggests that the Nino3 SST in winter and spring has a powerful influence on the occurrences of debris flows in the Xiaojiang River basin. It is found that the number of debris flows in Jiangjiagou Ravine is negatively correlated with January SST in the Nino3 region: it is smaller in El Nino phase years and larger in La Nina phase years. Because the Nino3 SST signal is at least 4 months ahead of debris flows, so it might provide an indicator for forecasting debris flows in the northern Yunnan. Particularly, it is possible to use the winter information of ENSO to predict debris flows in the subsequent summer in Xiaojiang River basin and its vicinity.