Advancing atmospheric river forecasts into subseasonal‐to‐seasonal time scales

Abstract

Atmospheric rivers are elongated plumes of intense moisture transport that are capable of producing extreme and impactful weather. Along the West Coast of North America, they occasionally cause considerable mayhem—delivering flooding rains during periods of heightened activity and desiccating droughts during periods of reduced activity. The intrinsic chaos of the atmosphere makes the prediction of atmospheric rivers at subseasonal‐to‐seasonal time scales (3 to 5 weeks) an inherently difficult task. We demonstrate here that the potential exists to advance forecast lead times of atmospheric rivers into subseasonal‐to‐seasonal time scales through knowledge of two of the atmosphere's most prominent oscillations, the Madden‐Julian oscillation (MJO) and the quasi‐biennial oscillation (QBO). Strong MJO and QBO activity modulates the frequency at which atmospheric rivers strike—offering an opportunity to improve subseasonal‐to‐seasonal forecast models and thereby skillfully predict atmospheric river activity up to 5 weeks in advance.

Atmospheric Blocking and Other Large‐Scale Precursor Patterns of Landfalling Atmospheric Rivers in the North Pacific: A CESM2 Study

“…() and Baggett et al. (; see those papers for full details of the AR detection algorithm). Those authors conducted sensitivity tests of IVT thresholds and report that the chosen values reliably outline AR filamentary plumes when visually compared to satellite imagery, although a degree of subjectivity is unavoidable.…”

“…Sources of influence affecting North Pacific ARs are found both in the tropics and extratropics. Regarding tropical sources, there is evidence that ARs are modulated by the Madden‐Julian oscillation (MJO; Guan et al., ; Madden & Julian, ; Mundhenk et al., ; Payne & Magnusdottir, ; Zhang, ), convectively coupled equatorial waves (Ralph et al., ), the quasi‐biennial oscillation (Baggett et al., ; Baldwin et al., ), and El Niño‐Southern Oscillation (Bao et al., ; Higgins et al., ).…”

Circulation Drivers of Atmospheric Rivers at the North American West Coast

“…Upper-level circulation observed during AR landfalls in Northern California (Neiman et (Neiman et al, 2008) feature a prominent high-low couplet with a gradient parallel to the coast, which acts to channel wind and moisture onshore. Recent work highlighted links between regional AR activity and circulation features associated with common teleconnection patterns such as the Pacific North American Pattern (PNA; Guan & Waliser, 2015), Arctic Oscillation (Guan et al, 2013), El Niño Southern Oscillation (ENSO; Ryoo et al, 2013;Kim & Alexander, 2015;Kim et al, 2017), Pacific Decadal Oscillation (PDO; GSR'17), Madden-Julian Oscillation (MJO; Guan & Waliser, 2015), and the MJO jointly with the quasi-biennial oscillation (Baggett et al, 2017;Mundhenk et al, 2018). Recent work highlighted links between regional AR activity and circulation features associated with common teleconnection patterns such as the Pacific North American Pattern (PNA; Guan & Waliser, 2015), Arctic Oscillation (Guan et al, 2013), El Niño Southern Oscillation (ENSO; Ryoo et al, 2013;Kim & Alexander, 2015;Kim et al, 2017), Pacific Decadal Oscillation (PDO; GSR'17), Madden-Julian Oscillation (MJO; Guan & Waliser, 2015), and the MJO jointly with the quasi-biennial oscillation (Baggett et al, 2017;Mundhenk et al, 2018).…”

Snow Level Characteristics and Impacts of a Spring Typhoon-Originating Atmospheric River in the Sierra Nevada, USA

“…Continuing research on understanding the interannual and interseasonal variability of typhoon-induced ARs and their relations to coupled modes of ocean-atmosphere climate variability is therefore recommended. Improving long-lead time forecasts of these high impact AR events appears feasible and would provide additional time for implementing flood risk mitigation strategies [43].…”