Alternative model of intense rainfall equation obtained from daily rainfall disaggregation

ABSTRACT The objective of this work was to propose an alternative model of IDF equation based on the disaggregation of daily rainfall. Data from the rainfall gauge station code 02649018 of the Brazilian National Water Agency from the period 1968 to 2011 were used. Several extreme event probability distributions were adjusted. Rainfall intensity with a return period of 2 to 100 years and durations of 5 to 1440 minutes were estimated using the relationships between rainfall for different durations. The four coefficients of the traditionally used IDF equation were adjusted, obtaining a sum of squares of deviations equal to 695.1 (mm.h-1)2 and standard error of estimation equal to 2.69 mm.h-1. For the model of the intense rainfall equation proposed, that relates the rain intensity and duration with the maximum daily rainfall, the sum of squares of the deviations was 33.6 (mm.h-1)2 and the standard estimated error was 0.59 mm.h-1. Including the return period in the model, we obtained squares of the deviations of 129.4 (mm.h-1)2, with a standard error of estimation of 1.16 mm.h-1. The models proposed have, besides better estimation accuracy, the advantages of facilitating the updating only by updating the maximum daily precipitation and sub serve the spatial representation.摘要 本研究旨在基于日降雨分解方法，提出一种降雨强度-历时-频率（Intensity-Duration-Frequency，IDF）方程的替代模型。本研究采用巴西国家水务局编号为02649018的雨量站1968年至2011年的观测数据，对多种极端事件概率分布进行了拟合校准。基于不同历时的降雨关系，估算了重现期2至100年、历时5至1440分钟的降雨强度。对传统常用的IDF方程的四个系数进行校准后，得到的偏差平方和为695.1 (mm·h⁻¹)²，估计标准误差为2.69 mm·h⁻¹。针对所提出的将降雨强度、历时与最大日降雨量相关联的强降雨方程模型，其偏差平方和为33.6 (mm·h⁻¹)²，估计标准误差为0.59 mm·h⁻¹。将重现期纳入模型后，得到的偏差平方和为129.4 (mm·h⁻¹)²，估计标准误差为1.16 mm·h⁻¹。所提出的模型不仅具备更优的估计精度，还拥有仅通过更新最大日降雨量即可便捷更新的优势，同时可辅助空间表征。