Value of Spatially Distributed Rainfall Design Events—Creating Basin-Scale Stochastic Design Storm Ensembles

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä

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en

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19

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Water (Switzerland), Volume 15, issue 17

Abstract

Current design storms used in hydrological modeling, urban planning, and dimensioning of structures are typically point-scale rainfall events with a steady rainfall intensity or a simple temporal intensity pattern. This can lead to oversimplified results because real rainfall events have more complex patterns than simple design series. In addition, the interest of hydrologists is usually in areal estimates rather than point values, most commonly in river-basin-wide areal mean rainfall estimates. By utilizing weather radar data and the short-term ensemble prediction system pySTEPS, which has so far been used for precipitation nowcasting, ensembles of high-resolution stochastic design storms with desired statistical properties and spatial structure evolving in time are generated. pySTEPS is complemented by adding time-series models for areal average rainfall over the simulation domain and field advection vectors. The selected study area is the Kokemäenjoki river basin located in Western Finland, and the model parametrization is carried out utilizing the Finnish Meteorological Institute’s weather radar data from the years 2013 to 2016. The results demonstrate how simulated events with similar large-scale mean areal rainfall can produce drastically different total event rainfalls in smaller scales. The sampling method, areal vs. gauge estimate, is also shown to have a prominent effect on total event rainfall across different spatial scales. The outlined method paves the way towards a more thorough and wide-spread assessment of the hydrological impacts of spatiotemporal rainfall characteristics.

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Funding Information: Radar precipitation observations used in this study were provided by the Finnish Meteorological Institute. The Optimal Rain Products with Dual-Pol Doppler Weather Radar (OSAPOL) project was funded by the European Regional Development Fund and the Finnish Funding Agency for Technology and Innovation (Tekes) (grant number 4459/31/2014). OSAPOL data are not publicly available. River basin data were retrieved from the open information service of the Finnish Environment Institute (Syke) [] and locations of gauge stations measuring hourly rainfall [] as well as rainfall intensity data for those gauges [] were obtained from the Finnish Meteorological Institute’s open research data service. Acknowledgments Funding Information: Ville Lindgren received funding from Maa-ja vesitekniikan tuki ry., grant number 32230; Aalto University, grant number 913672; and Sven Hallinin tutkimussäätiö sr. Publisher Copyright: © 2023 by the authors.

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Lindgren, V, Niemi, T, Koivusalo, H & Kokkonen, T 2023, 'Value of Spatially Distributed Rainfall Design Events—Creating Basin-Scale Stochastic Design Storm Ensembles', Water (Switzerland), vol. 15, no. 17, 3066. https://doi.org/10.3390/w15173066