From California’s Extreme Drought to Major Flooding: Evaluating and Synthesizing Experimental Seasonal and Subseasonal Forecasts of Landfalling Atmospheric Rivers and Extreme Precipitation during Winter 2022/23

California experienced a historic run of nine consecutive landfalling atmospheric rivers (ARs) in three weeks’ time during winter 2022/23. Following three years of drought from 2020 to 2022, intense landfalling ARs across California in December 2022–January 2023 were responsible for bringing reservoirs back to historical averages and producing damaging floods and debris flows. In recent years, the Center for Western Weather and Water Extremes and collaborating institutions have developed and routinely provided to end users peer-reviewed experimental seasonal (1–6 month lead time) and subseasonal (2–6 week lead time) prediction tools for western U.S. ARs, circulation regimes, and precipitation. Here, we evaluate the performance of experimental seasonal precipitation forecasts for winter 2022/23, along with experimental subseasonal AR activity and circulation forecasts during the December 2022 regime shift from dry conditions to persistent troughing and record AR-driven wetness over the western United States. Experimental seasonal precipitation forecasts were too dry across Southern California (likely due to their overreliance on La Niña), and the observed above-normal precipitation across Northern and Central California was underpredicted. However, experimental subseasonal forecasts skillfully captured the regime shift from dry to wet conditions in late December 2022 at 2–3 week lead time. During this time, an active MJO shift from phases 4 and 5 to 6 and 7 occurred, which historically tilts the odds toward increased AR activity over California. New experimental seasonal and subseasonal synthesis forecast products, designed to aggregate information across institutions and methods, are introduced in the context of this historic winter to provide situational awareness guidance to western U.S. water managers

Schematic representation of GO film—PDMS system.

<p>(a) Undeformed PDMS film; (b) strained PDMS film with aqueous solution GO drop casted on surface; (c) Buckled GO-PDMS system after partial release of strain in (b); (d) geometry of a single GO buckle due to the release of pre-strain.</p

Solid CAD models of AFM tensile tester (AMT1) components manufactured using additive manufacturing.

<p>(a) Frame. (b) Sample mount. (c) Brace.</p

Experimental profile and characterization of a representative buckle observed in the thick (≈ 200<i>nm</i>) GO film at 214% applied strain; Inset.

<p>AFM image depicting location of line scan used to measure buckle profile. The blue line indicates line scan orientation and the blue circle indicates the line scan origin.</p

Open-source micro-tensile testers via additive manufacturing for the mechanical characterization of thin films and papers - Fig 8

<p>AFM height images of buckled GO film deposited from 0.01 mg/mL (a and b, “thick” films) and 0.0025mg/mL solution (c and d, “thin” films). (a) 187% applied strain; (b) 159% applied strain;(c) 187% applied strain;(d) 159% applied strain. Blue arrows indicate buckles and red arrows indicate transverse cracking. The large white arrows indicate the direction of the compressive strain applied to the thin films for all the images.</p

Open-source micro-tensile testers via additive manufacturing for the mechanical characterization of thin films and papers - Fig 1

<p>(a) Fully formed GO paper manufactured via vacuum filtration[<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0197999#pone.0197999.ref017" target="_blank">17</a>] that was swollen and flash frozen with liquid nitrogen before lyophilization to remove the water allowing weak interlamellar regions to delaminate. Weak interlamellar regions near the paper surface are circled in red; (b) GO paper flash-frozen in the final stages of self-assembly (~90%) via vacuum-infiltration to highlight the substructures that exist in GO paper.</p

Open-source micro-tensile testers via additive manufacturing for the mechanical characterization of thin films and papers

<div><p>The cost of specialized scientific equipment can be high and with limited funding resources, researchers and students are often unable to access or purchase the ideal equipment for their projects. In the fields of materials science and mechanical engineering, fundamental equipment such as tensile testing devices can cost tens to hundreds of thousands of dollars. While a research lab often has access to a large-scale testing machine suitable for conventional samples, loading devices for meso- and micro-scale samples for in-situ testing with the myriad of microscopy tools are often hard to source and cost prohibitive. Open-source software has allowed for great strides in the reduction of costs associated with software development and open-source hardware and additive manufacturing have the potential to similarly reduce the costs of scientific equipment and increase the accessibility of scientific research. To investigate the feasibility of open-source hardware, a micro-tensile tester was designed with a freely accessible computer-aided design package and manufactured with a desktop 3D-printer and off-the-shelf components. To our knowledge this is one of the first demonstrations of a tensile tester with additively manufactured components for scientific research. The capabilities of the tensile tester were demonstrated by investigating the mechanical properties of Graphene Oxide (GO) paper and thin films. A 3D printed tensile tester was successfully used in conjunction with an atomic force microscope to provide one of the first quantitative measurements of GO thin film buckling under compression. The tensile tester was also used in conjunction with an atomic force microscope to observe the change in surface topology of a GO paper in response to increasing tensile strain. No significant change in surface topology was observed in contrast to prior hypotheses from the literature. Based on this result obtained with the new open source tensile stage we propose an alternative hypothesis we term ‘superlamellae consolidation’ to explain the initial deformation of GO paper. The additively manufactured tensile tester tested represents cost savings of >99% compared to commercial solutions in its class and offers simple customization. However, continued development is needed for the tensile tester presented here to approach the technical specifications achievable with commercial solutions.</p></div

Comparison between commercially available options and AMT1 developed in this study.

<p>Comparison between commercially available options and AMT1 developed in this study.</p

AFM compatible tensile tester (AMT1) in-situ under a Bruker Dimension Icon^™.

<p>AFM compatible tensile tester (AMT1) in-situ under a Bruker Dimension Icon^™.</p

Open-source micro-tensile testers via additive manufacturing for the mechanical characterization of thin films and papers - Fig 10

<p>(a) Experimental data and predicted trend lines for buckle amplitude and wavelength induced in thick film (~250nm) deposited from a 0.01mg/mL solution of GO. Each data point is generated from multiple height profiles across 2–6 buckles observed at each applied strain. The error bar indicates the standard error of the measured amplitude and wavelength data. (b) Experimental data and predicted trend lines for buckle amplitude and wavelength induced in a thin film (~50 nm) deposited from a 0.0025mg/mL solution of GO. Each data point is generated from height profiles across 2–9 buckles observed at each applied strain. The error bar indicates the standard error of the measured amplitude and wavelength data.</p