Ombrian curves advanced to stochastic modeling of rainfall intensity (Chapter 9)

D. Koutsoyiannis, and T. Iliopoulou, Ombrian curves advanced to stochastic modeling of rainfall intensity (Chapter 9), Rainfall Modeling, Measurement and Applications, 261–283, Elsevier, 2022.

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[English]

Ombrian curves, i.e. mathematic relationships linking average rainfall intensity to time scale of averaging and return period, also known as IDF (intensity-duration-frequency) curves, are essential tools in hydrology and engineering. Their use is supported by long-term hydrological experience, yet related formulas remain mostly empirical and lack a theoretical basis. As such, they entail several theoretical inconsistencies, particularly over large scales, while they cannot be applied in simulation. This Chapter reviews the typical form of ombrian curves along with its merits and limitations, and presents a modelling framework to overcome the latter by advancing curves to stochastic models of rainfall intensity. This is achieved through stochastic modelling of the joint second-order and marginal higher-order properties of the parent process. Two variants of the ombrian model are presented; a full version valid over time scales spanning multiple orders of magnitude, and a simplified relationship applicable over fine scales of the order of common applications, i.e. sub-hourly to daily. Specific emphasis is given to the fitting procedure combining multiple data sources and addressing bias in the estimation induced by temporal dependence. A detailed application of the ombrian model is performed for the rainfall station in Bologna (Italy), highlighting the efficiency of the resulting curves over multiple scales.

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See also: https://www.elsevier.com/books/rainfall/morbidelli/978-0-12-822544-8

Our works that reference this work:

1. T. Iliopoulou, N. Malamos, and D. Koutsoyiannis, Regional ombrian curves: Design rainfall estimation for a spatially diverse rainfall regime, Hydrology, 9 (5), 67, doi:10.3390/hydrology9050067, 2022.