Atmospheric River Tracking Method Intercomparison Project (ARTMIP): Project Goals and Experimental Design

Abstract

10The Atmospheric River Tracking Method Intercomparison Project (ARTMIP) is an international collaborative effort to understand and quantify the uncertainties in atmospheric river (AR) science based on detection algorithm alone. Currently, there are many AR identification and tracking algorithms in the literature with a wide range of techniques and conclusions. ARTMIP strives to provide the community with information on different 15 methodologies and provide guidance on the most appropriate algorithm for a given science question or region of interest. All ARTMIP participants will implement their detection algorithms on a specified common dataset for a defined period of time. The project is divided into two phases: Tier 1 will utilize the MERRA-2 reanalysis from January 1980 to June of 2017 and will be used as a baseline for all subsequent comparisons. Participation in Tier 1 is 20 required. Tier 2 will be optional and include sensitivity studies designed around specific science questions, such as reanalysis uncertainty and climate change. High resolution reanalysis and/or model output will be used wherever possible. Proposed metrics include AR frequency, duration, intensity, and precipitation attributable to ARs. Here we present the ARTMIP experimental design, timeline, project requirements, and a brief description of the 25 variety of methodologies in the current literature. We also present results from our 1-month "proof of concept" trial run designed to illustrate the utility and feasibility of the ARTMIP project.Geosci. Model Dev. Discuss., https://doi

Recent Warming of Landfalling Atmospheric Rivers Along the West Coast of the United States

“…Future work could expand the analysis to include additional reanalyses, as well as GCM simulations of the historical period. AR detection algorithm. As outlined in Shields et al (), algorithms for detecting AR presence use either absolute or relative vapor transport thresholds. Further, relative thresholds of IVT have been calculated from both anomalies (e.g., MBM16; Gorodetskaya et al, ; Shields & Kiehl, ) and percentiles (e.g., Brands et al, ; Guan & Waliser, ; Lavers et al, ).…”

“…Many AR catalogs have been developed using varying AR definitions, AR detection algorithms, and reanalysis data sets (Shields et al, ). We use an AR catalog (described in section .)…”

“…Atmospheric reanalysis products provide the capability to continuously measure ARs across the globe during the satellite era. Horizontal resolution plays a role in AR detection (Jackson et al, ; Shields et al, ), as algorithms may fail to detect ARs in low resolution products (Jackson et al, ). However, products with coarser spatial resolution have successfully been employed in AR studies (Guan & Waliser, ; Ralph et al, ).…”

“…The ERA‐Interim (ERA‐I; Dee, ), Modern‐Era Retrospective Analysis for Research and Applications (MERRA; Rienecker et al, ), and NCEP Climate System Forecast Reanalysis (CSFR; Saha et al, ) products have been documented in capturing AR characteristics found in satellite observations (Jackson et al, ), with ERA‐I exhibiting the smallest bias in AR frequency and landfall latitude. In order to evaluate the robustness of our results across multiple reanalysis data sets, we conduct our analysis on MERRA‐2 (the product on which the AR detection algorithm in Mundhenk et al, ,–hereafter MBM16–is run and the preferred product in the AR Tracking Method Intercomparison Project; Shields et al, ), along with ERA‐I (a product used in numerous AR studies; e.g., Guan & Waliser, ), and NCEP‐DOE R2 (a lower resolution product that also spans the satellite era). The horizontal resolution varies by product: ~0.5° × 0.5° for MERRA‐2, ~0.75° × 0.75° for ERA‐I, and 2.5° × 2.5° for NCEP‐DOE.…”

Impact of Atmospheric Rivers on Surface Hydrological Processes in Western U.S. Watersheds

“…All the analyses in this study are performed on a daily scale. The occurrence of ARs and their spatial coverage are taken from the Atmospheric River Tracking Method Intercomparison Project (ARTMIP; Shields et al, ). ARs tracked by the algorithm of Gershunov et al () applied to the MERRA‐2 reanalysis (Gelaro et al, ) are used in this study.…”