Abstract
The heavy precipitation in Northern California—brought about by a landfalling atmospheric river (AR) on 25–27 February 2019—is investigated for an understanding of the underlying dynamical processes. By the peaks in hourly accumulation, this rainstorm can be divided into two stages (Stage I and Stage II). Using a recently developed multiscale analysis methodology, i.e., multiscale window transform (MWT), and the MWT-based theory of canonical transfer, the original fields are reconstructed onto three scale windows, namely, the background flow, synoptic-scale and mesoscale windows, and the interactions among them are henceforth investigated. In both stages, the development of the precipitation is attributed to a vigorous buoyancy conversion and latent heating, and besides, the instability of the background flow. In Stage I, the instability is baroclinic, while in Stage II, it is barotropic. Interestingly, in Stage I, the mesoscale kinetic energy is transferred to the background flow where it is stored, and is released back in Stage II to the mesoscale window again, triggering intense precipitation.
Highlights
As an elongated and transient plume of strong horizontal water vapor transport, atmospheric rivers (ARs) are essential to the global water cycle [1,2], and play an important role in the occurrence of extreme precipitation and hydrological hazards [3,4,5]
Stage I while barotrUopsiincginastarebcileintytliyn-dSetavgeeloIpI.eCdolnosciadleirziendg mthue lftaiscctaillleusetnraetregdetbicysFaignuarlyes1i2satool, we investigated the dynamical processes underlying a heavy rainfall event in Northern ifornia associated with the landfalling atmospheric river (AR) during 25–27 Febr 2019
Using a recently-developed localized multiscale energetics analysis tool, we have investigated the dynamical processes underlying a heavy rainfall event in Northern California associated with the landfalling atmospheric river (AR) during 25–27 February 2019
Summary
As an elongated and transient plume of strong horizontal water vapor transport, atmospheric rivers (ARs) are essential to the global water cycle [1,2], and play an important role in the occurrence of extreme precipitation and hydrological hazards [3,4,5]. The purpose of this study was to explore the multiscale interactions underlying a heavy rainfall event in Northern California incurred by a landfalling AR on 25–27 February 2019 (see http://floodlist.com/america/usa/usa-california-russianriver-february-2019 for details, accessed on 10 September 2021).
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