Tagging moisture sources with Lagrangian and inertial tracers: application to intense atmospheric river events

Abstract

Abstract. Two Lagrangian tracer tools are evaluated for studies on atmospheric moisture sources and pathways. In these methods, a moisture volume is assigned to each particle, which is then advected by the wind flow. Usual Lagrangian methods consider this volume to remain constant and the particle to follow flow path lines exactly. In a different approach, the initial moisture volume can be considered to depend on time as it is advected by the flow due to thermodynamic processes. In this case, the tracer volume drag must be taken into account. Equations have been implemented and moisture convection was taken into account for both Lagrangian and inertial models. We apply these methods to evaluate the intense atmospheric rivers that devastated (i) the Pacific Northwest region of the US and (ii) the western Iberian Peninsula with flooding rains and intense winds in early November 2006 and 20 May 1994, respectively. We note that the usual Lagrangian method underestimates moisture availability in the continent, while active tracers achieve more realistic results.

Moisture transport contributing to precipitation at the centre of storm Bronagh

“…Atmospheric rivers have also been described using Lagrangian trajectories in an Earth‐relative framework, for example in Pérez‐Muñuzuri et al . (2018) and Sodemann et al . (2020).…”

“…Since they are defined using a vertically integrated measure, atmospheric rivers are 2-dimensional features. Atmospheric rivers have also been described using Lagrangian trajectories in an Earth-relative framework, for example in Pérez-Muñuzuri et al (2018) and Sodemann et al (2020).…”

Extreme precipitation events in the Mediterranean area: contrasting two different models for moisture source identification

“…While HPEs are a regional phenomena, moisture feeding them not only comes from nearby sea evaporation but can originate in remote regions and be transported by different atmospheric mechanisms. In this sense, it has been shown that long-distance moisture transport through atmospheric rivers (ARs) is a crucial contributor to total precipitation amounts recorded in Europe and the United States (e.g., Lavers and Villarini, 2015;Hu and Dominguez, 2019;Pérez-Muñuzuri et al, 2018) and also to extreme rainfall episodes (e.g., Stohl et al, 2008;Eiras-Barca et al, 2017). As for the WMR, recent studies (e.g., Winschall et al, 2012;Pinto et al, 2013;Krichak et al, 2015;Insua-Costa et al, 2019) suggest that remote sources of moisture such as the North Atlantic or tropical or subtropical areas could contribute significantly to the frequent torrential rains there.…”