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A Multi-Temporal-Scale Modulation Mechanism for the Post-Processing of Precipitation Ensemble Forecasts: Benefits for Streamflow Forecasting
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2023
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Source: Journal of Hydrometeorology (2023)
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Journal Title:Journal of Hydrometeorology
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Description:In the post-processing of ensemble forecasts of weather variables, it is standard practice to first calibrate the forecasts in a univariate setting, before reconstructing multivariate ensembles that have a correct covariabilty in space, time, and across variables, via so-called ”reordering” methods. Within this framework though, post-processors cannot fully extract the skill of the raw forecast that may exist at larger scales. A multi-temporal-scale modulation mechanism for precipitation is here presented, which aims at improving the forecasts over different accumulation periods, and which can be coupled with any univariate calibration and multivariate reordering techniques. The idea, originally known under the term ”canonical events”, has been implemented for more than a decade in the Meteorological Ensemble Forecast Processor (MEFP), a component of the U.S. National Weather Service (NWS)’s Hydrologic Ensemble Forecast Service (HEFS), although users were left with material in the grey literature. This paper proposes a formal description of the mechanism, and studies its intrinsic connection with the multivariate reordering process. The verification of modulated and unmodulated forecasts, when coupled with two popular methods for reordering, the Schaake shuffle and ensemble copula coupling (ECC), is performed on 11 Californian basins, on both precipitation and streamflow. Results demonstrate the clear benefit of the multi-temporal-scale modulation, in particular on multi-day total streamflow. However, the relative gain depends on the method used for reordering, with more benefits expected when this latter method is not able to reconstruct an adequate temporal structure on the calibrated precipitation forecasts.
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Source:Journal of Hydrometeorology (2023)
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DOI:
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ISSN:1525-755X;1525-7541;
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Rights Information:Other
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Compliance:Library
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