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Abstract While challenging, quantification of the near‐surface landfalling hurricane wind field is necessary for understanding hurricane intensity changes and damage potential. Using single‐ and dual‐Doppler Doppler on Wheels and in situ anemometer data, the wind structure of the very near‐surface boundary layer of Hurricane Laura (2020) is characterized. Small‐scale hurricane boundary layer (HBL) rolls (HBLRs) with a median size of approximately 400 m are present throughout much of the landfall, but are most vigorous in the eyewall. The maximum turbulent kinetic energy (TKE) and momentum flux associated with HBLRs occur in the eyewall and are much larger than previously documented at landfall. DOW‐derived and anemometer‐derived TKE values are comparable. Observed maximum surface gusts were consistent with the maximum radar wind speeds aloft, suggesting the importance of vertical transport within the HBL by sub‐kilometer scale structures for the enhancement of surface wind speeds. 

In this work we demonstrate that accurate ground state wave functions may be constructed for polarons in a fully ab initio setting across the wide range of couplings associated with both the large and small polaron limits. We present a single general unitary transformation approach which encompasses an ab initio version of the Lee-Low-Pines theory at weak coupling and the coherent state Landau-Pekar framework at strong coupling while interpolating between these limits in general cases. We show that perturbation theory around these limits may be performed in a facile manner to assess the accuracy of the approach, as well as provide an independent route to the ab initio properties of polarons. We test these ideas on the case of LiF, where the electron-polaron is expected to be large and relatively weakly coupled, while the hole-polaron is expected to be a strongly coupled small polaron. 

Alloys of tungsten tetraboride (WB4) with the addition of C and Si were prepared by arc-melting of the constituent elements. The phase purity was established by powder X-ray diffraction (PXRD) and surface morphology by scanning electron microscopy (SEM) analysis. Vickers hardness measurements showed hardness enhancement for alloys with a nominal composition of (W0.98Si0.02):11.6B and (W0.95C0.05):11.6B of 52.2 ± 3.0 and 50.5 ± 2.5 GPa, respectively, compared to 41.2 ± 1.4 GPa for pure WB4. (W0.92Zr0.08):11.6B was determined in previous work to have a hardness of 55.9 ± 2.8 GPa. Bulk moduli were calculated following analysis of high-pressure radial diffraction data and were determined to be 329 ± 4 (K0′ = 2) and 390 ± 9 (K0′ = 0.6) GPa for 8 atom % Zr and 5 atom % C-doping, respectively, compared to 326–339 GPa for pure WB4. Computational analysis was used to determine the dopant positions in the crystal structure, and it was found that Zr primarily substitutes W in the 2c position, Si substitutes for the entire B3 trimers, and C inserts in the Bhex-layer. The hardness enhancement in the case of Zr-doping is attributed primarily to extrinsic hardness effects (nanograin morphology), in the case of C─to intrinsic effects (interlayer bond strengthening), and in the intermediate case of Si─to both intrinsic and extrinsic effects (bond strengthening and fine surface morphology). 

Abstract Quasi-linear convective systems (QLCSs) are responsible for approximately a quarter of all tornado events in the U.S., but no field campaigns have focused specifically on collecting data to understand QLCS tornadogenesis. The Propagation, Evolution, and Rotation in Linear System (PERiLS) project was the first observational study of tornadoes associated with QLCSs ever undertaken. Participants were drawn from more than 10 universities, laboratories, and institutes, with over 100 students participating in field activities. The PERiLS field phases spanned two years, late winters and early springs of 2022 and 2023, to increase the probability of intercepting significant tornadic QLCS events in a range of large-scale and local environments. The field phases of PERiLS collected data in nine tornadic and nontornadic QLCSs with unprecedented detail and diversity of measurements. The design and execution of the PERiLS field phase and preliminary data and ongoing analyses are shown. 

Abstract Data from scanning radars, radiosondes, and vertical profilers deployed during three field campaigns are analyzed to study interactions between cloud-scale updrafts associated with initiating deep moist convection and the surrounding environment. Three cases are analyzed in which the radar networks permitted dual-Doppler wind retrievals in clear air preceding and during the onset of surface precipitation. These observations capture the evolution of: i) the mesoscale and boundary layer flow, and ii) low-level updrafts associated with deep moist convection initiation (CI) events yielding sustained or short-lived precipitating storms. The elimination of convective inhibition did not distinguish between sustained and unsustained CI events, though the vertical distribution of convective available potential energy may have played a role. The clearest signal differentiating the initiation of sustained versus unsustained precipitating deep convection was the depth of the low-level horizontal wind convergence associated with the mesoscale flow feature triggering CI, a sharp surface wind shift boundary or orographic upslope flow. The depth of the boundary layer relative to the height of the LFC failed to be a consistent indicator of CI potential. Widths of the earliest detectable low-level updrafts associated with sustained precipitating deep convection were ~3-5 km, larger than updrafts associated with surrounding boundary layer turbulence (~1-3-km wide). It is hypothesized that updrafts of this larger size are important for initiating cells to survive the destructive effects of buoyancy dilution via entrainment. 

Lode gold deposits, which are currently the world’s major gold supply, have been shown to be generated mostly by phase separation of metamorphic fluids and/or interaction between these fluids and wall rocks. Here we use garnet oxygen isotopes by secondary ion mass spectrometry to document the crucial role of magmatic hydrothermal fluids and their mixing with meteoric water in the formation of the world-class Dongping gold deposit in the North China Craton. Garnet grains from quartz veins of various paragenetic stages and the mineralized alteration envelope at Dongping have dynamic δ 18 O variations of 3.8 to −11.0‰, with large intragrain fluctuations up to 5.3‰. These values correspond to calculated δ 18 O values of 6.1 to −9.1‰ for the hydrothermal fluids from which the garnet formed. The isotope data, notably the cyclic alternation in δ 18 O within individual garnet grains, are best interpreted to reflect multiple pulses of magmatically derived fluids and subsequent mixing of each pulse with variable amounts of meteoric water. The results presented here allow us to quantify the significant interplay between magmatic hydrothermal fluids and meteoric water that spanned the entire mineralization history and triggered gold deposition of a lode gold deposit. This study highlights the potential use of in situ oxygen isotope analysis of garnet in tracing the origin and evolution of hydrothermal fluids in the Earth’s crust that may have formed other giant ore deposits.