Heavy Rainfall Mapping for Tocantins State, Brazil

Abstract This study aimed to map heavy rainfall with durations of 10, 30, 720 and 1440 minutes, associated with return times of 10, 50 and 100 years for the Tocantins State. Historical series of 95 pluviometric stations located in the Tocantins State and nearby were applied, with standard period from 1983 to 2013. A geostatistical study was conducted, evaluating the spherical, exponential and gaussian semivariogram models, adjusted by the weighted least squares method. From this study, the model that presented the smallest average error based on cross-validation was applied to the mapping process by ordinary kriging. There was good performance of the geostatistical techniques, being possible to highlight the spherical model for the mapping of the annual maximum daily precipitation and the Gaussian model for the rains calculated by the methodology of disaggregation. It was also verified that the areas of intense rainfall of greater severity in the state are in the Bico do Papagaio (north), Bananal Island (southwest) and northwest of the state.

摘要 本研究旨在针对巴西托坎廷斯州，绘制持续时长分别为10、30、720及1440分钟的强降雨空间分布图，该类强降雨对应10、50与100年一遇的重现期。研究采用了托坎廷斯州及周边地区共95个雨量站的历史观测序列，其标准观测周期为1983年至2013年。本研究开展了地统计学分析，对球状、指数及高斯半变异函数模型（semivariogram model）进行了评估，上述模型均通过加权最小二乘法（weighted least squares method）完成拟合。基于交叉验证（cross-validation）得到的结果，选取平均误差最小的模型，借助普通克里金法（ordinary kriging）完成空间制图流程。地统计学技术展现出优异的应用性能，其中球状模型适配年最大日降水量的空间制图，高斯模型则适用于通过分解法计算得到的降雨事件。研究同时证实，托坎廷斯州内强降雨烈度更高的高发区域位于北部的鹦鹉喙（Bico do Papagaio）、西南部的巴纳纳尔岛（Bananal Island）以及该州西北部地带。