基于EOF和MK趋势分析的赣江流域降水时空分布格局

Spatiotemporal Distribution Pattern of Precipitation in Ganjiang River Basin Based on EOF and MK Trend Analysis

[目的]研究赣江流域降水的时空分布特征,明确流域上中下游地区不同等级降雨的年际、年内和空间变化规律,并揭示易引发洪涝灾害的大雨和暴雨的高发时段和集中分布区域。[方法]使用经验正交函数分析(EOF)和Mann-Kendall(MK)非参数检验等方法对全流域和上中下游降水量以及不同等级降水进行了分类与统计研究。[结果](1)对赣江流域降水空间分布格局的分析发现,降雨的高值中心位于流域东南部的宁都和石城地区,以此为起点向南北两个方向逐渐递减;大雨和暴雨的高值中心也主要位于流域东部及其偏南地区,由此向南北递减;中雨和小雨的高值中心则与之相反,主要位于流域西部及其偏南地区。(2)赣江流域降水的年际趋势变化显示,流域整体降水量呈现不显著增加趋势,仅3个站点和下游区域的降雨量有显著增加趋势;不同等级降雨中,小雨表现为显著下降趋势,中雨整体表现为不显著下降趋势(下游除外),大雨和暴雨在全流域及其不同分区都表现为显著增加趋势。(3)不同等级降雨的年内变化显示,全年降雨量主要集中发生于汛期,中雨和大雨为主要降水类型;6月降水最多,尤其是暴雨量显著大于其他月份,12月降雨量最少。[结论]赣江流域降水呈现出小雨中雨减少,大雨暴雨显著增加的两极分化现象,且呈现明显的时空分布不均现象;以石城和瑞金为起点的流域东南部地区在主汛期(尤其是6月)发生区域性暴雨洪涝灾害的概率较大。

[Objective]The aim of this article is to study the spatiotemporal distribution characteristic of precipitation in the Ganjiang River basin,clarify the inter-annual,intra annual and spatial variation laws of different levels of rainfall in the upper,middle and lower reaches of the basin,and then reveal the high incidence period and concentrated distribution area of both heavy rainfall and rainstorm that are prone to flood disasters.[Methods]The precipitation of the whole basin and the upper,middle and lower reaches and different grades of precipitation were classified and statistically studied by EOF analysis and Mann-Kendall(MK)non-parametric tests.[Results](1)The analysis of the spatial distribution characteristics of precipitation in the Ganjiang River Basin found that the center of the high value of rainfall was located in the Ningdu and Shicheng areas in the southeast of the river basin,and gradually decreased in the north and south directions from this starting point.The high-value centers of heavy rain and rainstorm were also mainly located in the eastern part and its further south region,and decreased to the south and north from this point,while the high value centers of moderate rain and light rain were opposite,which were mainly located in the western part of the river basin and its further southern regions.(2)The change of the interannual trend of precipitation in the whole basin showed that the total precipitation showed no significant increase trend,and only 3 stations and downstream areas had a significant increase trend.Among the different grades rainfall,light rainfall showed a significant downward trend,moderate rain as a whole showed a non-significant downward trend(except the downstream area),heavy rainfall and rainstorm showed a significant increase trend in the whole basin and its subarea.(3)The annual changes of different grades of rainfall showed that the annual rainfall mainly occurred in the flood season,with moderate and heavy rainfall as the main precipitation types.The rainfall in June was the most,especially the rainstorm in June was significantly greater than that in other months,and the rainfall in December was the least.[Conclusion]The precipitation in the Ganjiang River Basin showed a polarization phenomenon of light and moderate rainfall decreased,heavy rainfall and rainstorm increased significantly,and there is an obvious uneven spatial and temporal distribution.The southeastern part of the basin,starting from Shicheng and Ruijin,is more likely to experience regional rainstorm and floods disasters during the main flood season,especially in June.