Ranking Atmospheric Rivers: New Study Finds World of Potential

March 21, 2023

In a new study, titled Global Application of the Atmospheric River Scale, CW3E collaborators Bin Guan (UCLA) and Duane E. Waliser (JPL), along with CW3E director Marty Ralph explore a wider geographic application of the atmospheric river (AR) scale for characterizing strength and communicating potential impacts of ARs. This work contributes to the goals of CW3E’s 2019-2024 Strategic Plan to lead AR Research and Applications because the paper proposes the first globally uniform AR scale for facilitating communication about ARs and intercomparing across different regions.

Read more about this study here.

(a) Examples of atmospheric river (AR) ranking (color shading) based on all ARs detected by tARget version 3 (referred to as the algorithm method) at an arbitrary 6-hr time step of the MERRA-2 reanalysis. Each contiguous area indicates a unique AR. Gray shading indicates grid cells that fall within the boundary of ARs detected by the algorithm, but did not receive an AR rank due to failing integrated water vapor transport (IVT) intensity and/or event duration thresholds; see Section 2 for details. The unfilled (filled) circles mark selected coastal (oceanic) areas used in subsequent analysis. (b) A specific AR from panel (a). Color shading shows the maximum IVT of the event at each grid cell, with the color corresponding to the AR rank if the event duration is between 24 and 48 hr. White (black) outlines show locations where the event is <24 hr (≥48 hr), for which the actual AR rank will be decreased (increased) by 1 from that implied by the color shading. Gray shading indicates locations not considered for AR ranking due to not meeting duration (12 hr) and/or IVT (250 kg m⁻¹ s⁻¹) thresholds. (c) The actual AR ranks received at each grid cell for the case shown in panel (b) after the duration-based adjustments mentioned above are made at the locations marked by white/black outlines. The white/black outlines are repeated from panel (b) to facilitate comparisons.