Interval-Censored Survival Analysis of Grapevine Phenology: Thermal Controls on Flowering and Fruit Ripening

Abstract

European grapevine (\textit{Vitis vinifera} L.) is a climate-sensitive perennial whose flowering and ripening govern yield and quality. Phenological records from monitoring programs are typically collected at irregular intervals, so true transition dates are interval-censored, and many site-years are right-censored. We develop a reproducible workflow that treats phenology as a time-to-event outcome: Status \& Intensity observations from the USA-NPN are converted to interval bounds, linked to NASA POWER daily weather, and analyzed with parametric accelerated failure time (AFT) models (Weibull and log-logistic). To avoid outcome-dependent bias from aggregating weather up to the event date, antecedent conditions are summarized in fixed pre-season windows and standardized; quality-control filters ensure adequate within-window data coverage. Applied to flowering and ripening of \textit{V.~vinifera}, the framework yields interpretable time-ratio effects and publication-ready tables and figures. Warmer pre-season conditions are associated with earlier ripening, whereas flowering responses are modest and uncertain in these data; precipitation plays, at most, a secondary role. The approach demonstrates how interval-censored survival models with exogenous weather windows can extract robust climate signals from citizen-science phenology while preserving observation uncertainty, and it generalizes readily to other species and networks.