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The mass reduction of passenger vehicles has been a great focus of academic research and federal policy initiatives of the United States with coordinated funding efforts and even a focus of a Manufacturing USA Institute. The potential benefit of these programs can be described as modest from a societal point of view, for example reducing vehicle mass by up to 25% with modest cost implications (under $5 per pound saved) and the ability to implement with existing manufacturing methods. Much more aggressive reductions in greenhouse gas production are necessary and possible, while delivering the same service. This is demonstrated with a higher-level design thinking exercise on an environmentally responsible lightweight vehicle, leading to the following criteria: lightweight, low aerodynamic drag, long-lived (over 30 years and 2 million miles), adaptable, electric, and used in a shared manner on average over 8 h per day. With these specifications, passenger-mile demand may be met with around 1/10 of the current fleet. Such vehicles would likely have significantly different designs and construction than incumbent automobiles. It is likely future automotive production will be more analogous to current aircraft production with higher costs per pound and lower volumes, but with dramatically reduced financial and environmental cost per passenger mile, with less material per vehicle, and far less material required in the national or worldwide fleets. Subsidiary benefits of this vision include far fewer parking lots, greater accessibility to personal transportation, and improved pedestrian safety, while maintaining a vibrant and engaging economy. The systemic changes to the business models and research and development directions (including lightweight design and manufacturing) are discussed, which could bring forth far more sustainable personal transportation.

 

Abstract The energy and momentum balance of an abyssal overflow across a major sill in the Samoan Passage is estimated from two highly resolved towed sections, set 16 months apart, and results from a two-dimensional numerical simulation. Driven by the density anomaly across the sill, the flow is relatively steady. The system gains energy from divergence of horizontal pressure work and flux of available potential energy . Approximately half of these gains are transferred into kinetic energy while the other half is lost to turbulent dissipation, bottom drag, and divergence in vertical pressure work. Small-scale internal waves emanating downstream of the sill within the overflow layer radiate upward but dissipate most of their energy within the dense overflow layer and at its upper interface. The strongly sheared and highly stratified upper interface acts as a critical layer inhibiting any appreciable upward radiation of energy via topographically generated lee waves. Form drag of , estimated from the pressure drop across the sill, is consistent with energy lost to dissipation and internal wave fluxes. The topographic drag removes momentum from the mean flow, slowing it down and feeding a countercurrent aloft. The processes discussed in this study combine to convert about one-third of the energy released from the cross-sill density difference into turbulent mixing within the overflow and at its upper interface. The observed and modeled vertical momentum flux divergence sustains gradients in shear and stratification, thereby maintaining an efficient route for abyssal water mass transformation downstream of this Samoan Passage sill. 

Abstract. Extensive airborne measurements of non-methane organic gases (NMOGs), methane, nitrogen oxides, reduced nitrogen species, and aerosol emissions from US wild and prescribed fires were conducted during the 2019 NOAA/NASA Fire Influence on Regional to Global Environments and Air Quality campaign (FIREX-AQ). Here, we report the atmospheric enhancement ratios (ERs) and inferred emission factors (EFs) for compounds measured on board the NASA DC-8 research aircraft for nine wildfires and one prescribed fire, which encompass a range of vegetation types. We use photochemical proxies to identify young smoke and reduce the effects of chemical degradation on our emissions calculations. ERs and EFs calculated from FIREX-AQ observations agree within a factor of 2, with values reported from previous laboratory and field studies for more than 80 % of the carbon- and nitrogen-containing species. Wildfire emissions are parameterized based on correlations of the sum of NMOGs with reactive nitrogen oxides (NOy) to modified combustion efficiency (MCE) as well as other chemical signatures indicative of flaming/smoldering combustion, including carbon monoxide (CO), nitrogen dioxide (NO2), and black carbon aerosol. The sum of primary NMOG EFs correlates to MCE with an R2 of 0.68 and a slope of −296 ± 51 g kg−1, consistent with previous studies. The sum of the NMOG mixing ratios correlates well with CO with an R2 of 0.98 and a slope of 137 ± 4 ppbv of NMOGs per parts per million by volume (ppmv) of CO, demonstrating that primary NMOG emissions can be estimated from CO. Individual nitrogen-containing species correlate better with NO2, NOy, and black carbon than with CO. More than half of the NOy in fresh plumes is NO2 with an R2 of 0.95 and a ratio of NO2 to NOy of 0.55 ± 0.05 ppbv ppbv−1, highlighting that fast photochemistry had already occurred in the sampled fire plumes. The ratio of NOy to the sum of NMOGs follows trends observed in laboratory experiments and increases exponentially with MCE, due to increased emission of key nitrogen species and reduced emission of NMOGs at higher MCE during flaming combustion. These parameterizations will provide more accurate boundary conditions for modeling and satellite studies of fire plume chemistry and evolution to predict the downwind formation of secondary pollutants, including ozone and secondary organic aerosol.

 

Axial Seamount is a seafloor volcano with frequent eruptions and periodic cycles of inflation and deflation. Seafloor pressure gauges monitor vertical deformation with time, but inherent instrumental drift complicates and biases geodetic interpretation. A drift corrected pressure recorder was deployed on Axial Seamount on 6 July 2018, at coordinates 45° 57.29′ North latitude, −130° 0.56′ East longitude, depth 1,535 m. This system includes two independent quartz‐resonant pressure gauges, which nearly continuously observe the seafloor pressure. At regular intervals, the gauges are calibrated in situ with a modified deadweight tester at a pressure within 98% of the nominal seafloor pressure. Using the calibration data, the drift of each gauge has been modeled as a simple linear plus decaying exponential function of time. The two estimated linear sensor drift rates are 0.45 ± 0.12 and 0.36 ± 0.08 kPa/year; the modeled sensor drift represents a significant error if uncorrected. The standard deviations of the drift model residuals are of order 0.06 kPa or 6 mm depth equivalent. Once calibrated, the difference between the two seafloor pressure timeseries exhibits a RMS deviation of ±6 mm at the 90% confidence limit and a linear trend less than 1 mm/year. A time series from July 2018 to December 2021 tracks the inflation of Axial Seamount with differing inflation rates over different time intervals.

 

The boundary between the overriding and subducting plates is locked along some portions of the Cascadia subduction zone. The extent and location of locking affects the potential size and frequency of great earthquakes in the region. Because much of the boundary is offshore, measurements on land are incapable of completely defining a locked zone in the up‐dip region. Deformation models indicate that a record of seafloor height changes on the accretionary prism can reveal the extent of locking. To detect such changes, we have initiated a series of calibrated pressure measurements using an absolute self‐calibrating pressure recorder. A piston‐gauge calibrator under careful metrological considerations produces an absolutely known reference pressure to correct seafloor pressure observations to an absolute value. We report an accuracy of about 25 ppm of the water depth, or 0.02 kPa (0.2 cm equivalent) at 100 m to 0.8 kPa (8 cm equivalent) at 3,000 m. These campaign survey‐style absolute pressure measurements on seven offshore benchmarks in a line extending 100 km westward from Newport, Oregon from 2014 to 2017 establish a long‐term, sensor‐independent time series that can, over decades, reveal the extent of vertical deformation and thus the extent of plate locking and place initial limits on rates of subsidence or uplift. Continued surveys spanning years could serve as calibration values for co‐located or nearby continuous pressure records and provide useful information on possible crustal deformation rates, while epoch measurements spanning decades would provide further limits and additional insights on deformation.

 

Abstract. Glyoxal (CHOCHO), the simplest dicarbonyl in thetroposphere, is a potential precursor for secondary organic aerosol (SOA)and brown carbon (BrC) affecting air quality and climate. The airbornemeasurement of CHOCHO concentrations during the KORUS-AQ (KORea–US AirQuality study) campaign in 2016 enables detailed quantification of lossmechanisms pertaining to SOA formation in the real atmosphere. Theproduction of this molecule was mainly from oxidation of aromatics (59 %)initiated by hydroxyl radical (OH). CHOCHO loss to aerosol was found to bethe most important removal path (69 %) and contributed to roughly∼ 20 % (3.7 µg sm−3 ppmv−1 h−1,normalized with excess CO) of SOA growth in the first 6 h in SeoulMetropolitan Area. A reactive uptake coefficient (γ) of∼ 0.008 best represents the loss of CHOCHO by surface uptakeduring the campaign. To our knowledge, we show the first field observationof aerosol surface-area-dependent (Asurf) CHOCHO uptake, which divergesfrom the simple surface uptake assumption as Asurf increases in ambientcondition. Specifically, under the low (high) aerosol loading, the CHOCHOeffective uptake rate coefficient, keff,uptake, linearly increases(levels off) with Asurf; thus, the irreversible surface uptake is areasonable (unreasonable) approximation for simulating CHOCHO loss toaerosol. Dependence on photochemical impact and changes in the chemical andphysical aerosol properties “free water”, as well as aerosol viscosity,are discussed as other possible factors influencing CHOCHO uptake rate. Ourinferred Henry's law coefficient of CHOCHO, 7.0×108 M atm−1, is ∼ 2 orders of magnitude higher than thoseestimated from salting-in effects constrained by inorganic salts onlyconsistent with laboratory findings that show similar high partitioning intowater-soluble organics, which urges more understanding on CHOCHO solubilityunder real atmospheric conditions. 

Semiconductor quantum dots embedded in micropillar cavities are excellent emitters of single photons when pumped resonantly. Often, the same spatial mode is used to both resonantly excite a quantum-dot state and to collect the emitted single photons, requiring cross polarization to reduce the uncoupled scattered laser light. This inherently reduces the source brightness to 50%. Critically, for some quantum applications the total efficiency from generation to detection must be over 50%. Here, we demonstrate a resonant-excitation approach to creating single photons that is free of any cross polarization, and in fact any filtering whatsoever. It potentially increases single-photon rates and collection efficiencies, and simplifies operation. This integrated device allows us to resonantly excite single quantum-dot states in several cavities in the plane of the device using connected waveguides, while the cavity-enhanced single-photon fluorescence is directed vertically (off-chip) in a Gaussian mode. We expect this design to be a prototype for larger chip-scale quantum photonics.

 

Abstract. Fires emit sufficient sulfur to affect local and regional airquality and climate. This study analyzes SO2 emission factors andvariability in smoke plumes from US wildfires and agricultural fires, as well as theirrelationship to sulfate and hydroxymethanesulfonate (HMS) formation.Observed SO2 emission factors for various fuel types show goodagreement with the latest reviews of biomass burning emission factors,producing an emission factor range of 0.47–1.2 g SO2 kg−1 C.These emission factors vary with geographic location in a way that suggeststhat deposition of coal burning emissions and application ofsulfur-containing fertilizers likely play a role in the larger observedvalues, which are primarily associated with agricultural burning. A 0-D boxmodel generally reproduces the observed trends of SO2 and total sulfate(inorganic + organic) in aging wildfire plumes. In many cases, modeled HMSis consistent with the observed organosulfur concentrations. However, acomparison of observed organosulfur and modeled HMS suggests that multipleorganosulfur compounds are likely responsible for the observations but thatthe chemistry of these compounds yields similar production and loss rates asthat of HMS, resulting in good agreement with the modeled results. Weprovide suggestions for constraining the organosulfur compounds observedduring these flights, and we show that the chemistry of HMS can alloworganosulfur to act as an S(IV) reservoir under conditions of pH > 6 and liquid water content>10−7 g sm−3. This canfacilitate long-range transport of sulfur emissions, resulting in increasedSO2 and eventually sulfate in transported smoke.