A non arbitrary definition of rain event: the case of stratiform rain

TL;DR

This paper proposes a non-arbitrary, statistically justified definition of rain events specifically for stratiform rain, based on the duration of rainless periods, with implications for hydrological analysis.

Contribution

It demonstrates the equivalence of different rain event definitions and identifies an optimal rainless period range for stratiform rain, providing a more objective framework.

Findings

Event definitions based on rainless periods and consecutive wet intervals are statistically equivalent.

For stratiform rain, a 1.5 to 4-hour rainless period is optimal for defining events.

Stratiform rain exhibits alternating quiescent and active phases, characterizing intra-event variability.

Abstract

A long standing issue in Hydrology is the arbitrariness of the rain "event" definition. In this manuscript, we show that 1) the event definition resting on the occurrence of a minimum rainless period and the one resting a sequence of consecutive wet intervals are statistically equivalent. 2) In the case of stratiform rain, a non arbitrary definition of rain event is possible. The dynamical properties of stratiform rain indicate the range [1.5,4] h as the proper one for the choice of a minimum rainless period for Chilbolton, UK. 3) The intra event dynamical variability is "described" by an alternate sequence of quiescent and active phases.