ENSO对珠江三角洲洪水影响

根据珠江三角洲1951—2008年34个潮位站年极高水位资料和Nino 3.4区海洋尼诺指数资料，采用GEV分布进行洪水频率计算，分析不同重现期洪水位的变化情况，对比分析洪水位重现水平在1980年前后空间变化特征。采用滑动相关分析，探讨珠江三角洲近50年来洪水位对ENSO(El Nino/La Nisa-Southern Oscillation)响应的年际变化特征。结果表明，珠江三角洲整个区域的洪水频率分布自下游到上游逐渐增大，沿海比中上游地区更易受洪涝灾害威胁。绝大多数站点不同重现期洪水位变化趋势一致，部分站点水位变化方向不完全一致。洪水位有减小趋势的站点分布在三角洲上游地区，中下游地区则主要呈现为增长趋势。洪水位与ENSO之间年际变化关系有明显阶段性，在1980年发生明显改变，跃变前后滑动相关系数的符号或强度有明显差异。洪水位对不同季节的ENSO响应不同，不同时期ENSO对洪水位的影响不同。

Impacts of ENSO on different flood frequencies in Pearl River delta

Based on annual maximum water level (AMWL) data obtained from 34 gauging stations in the Pearl River delta (PRD) and the oceanic Nino index (ONI) data in the Nino 3.4 region from 1951 to 2008, the GEV distribution model is used to get the flood frequency analysis of AMWL. In order to comprehensively understand the water level fluctuations characteristics in the delta, the water level variation corresponding to different flood frequencies calculated from a series of pre 1980 and post 1980 years are examined. The studies of interdecadal variations in the response of the flood water level to ENSO in the past fifty years have been carried out by using moving correlation. The space time variations in the flood water levels corresponding to different return periods in the PRD region suggest that the flood water level increases gradually from the coastal areas to the riverine system. The flood frequency variations have shown that the most serious flood risk is in the coastal region because this region is extremely vulnerable to the flood hazards. The flood water level increments corresponding to different increments of the flood periods in all 34 sites are great. In the upper PRD, the flood water levels show a decreasing trend while there is an increasing trend in the middle and lower PRD. The long term variation of interannual relationships between ENSO and the flood water level has a significant stage characteristic and has a great change in the 1980s. Before and after the abrupt change, the correlation coefficients have remarkable differences. The flood water levels have various responses to various seasonal ENSO events.