30 May 2024
 | 30 May 2024
Status: this preprint is open for discussion.

Modelling convective cell lifecycles with a copula-based approach

Chien-Yu Tseng, Li-Pen Wang, and Christian Onof

Abstract. This study proposes an algorithm designed to model convective cell lifecycles, for the purpose of improving the representation of convective storms in rainfall modelling and forecasting. We propose to explicitly model cell property inter-dependence and temporal evolution. To develop the algorithm, 165 effective convective storm events occurring between 2005 and 2017 in Birmingham, UK, were selected. A state-of-the-art storm tracking algorithm was employed to reconstruct convective cell lifecycles within each selected event. The investigation of these cell lifecycles proceeded in three stages. The initial stage involved statistically characterising individual properties of convective cells, including rainfall intensity, spatial extent at peaks, and lifespan. Subsequently, an examination of the inter-correlations amongst these properties was conducted. In the final stage, the focus was on examining the evolution of these cell properties during their lifetimes. We found that the growth and decay rates of cell properties are correlated with the cell properties themselves. Hence the need to incorporate this correlation structure into the process of sampling convective cells. To resolve the dependence structures within convective cell evolution, a novel algorithm based on vine copulas is proposed. We show the proposed algorithm's ability to sample cell lifecycles preserving both observed individual cell properties and their dependence structures. To enhance the algorithm's applicability, it is linked to an exponential shape model to synthesise spatial fields of rainfall intensity for each cell. This defines a model which can readily be incorporated into rainfall generators and forecasting tools.

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Chien-Yu Tseng, Li-Pen Wang, and Christian Onof

Status: open (until 25 Jul 2024)

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Chien-Yu Tseng, Li-Pen Wang, and Christian Onof
Chien-Yu Tseng, Li-Pen Wang, and Christian Onof


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Short summary
This study presents a new algorithm to better model convective storms. We used advanced tracking methods to analyse 165 storm events in Birmingham (UK) and to reconstruct storm cell lifecycles. We found that cell properties like intensity and size are interrelated and vary over time. The new algorithm, based on vine copulas, accurately simulates these properties and their evolution. It also integrates an exponential model for realistic rainfall patterns, enhancing its hydrological applicability.