ALBERT

Description: We present an analytical protocol for in situ U–Pb isotope dating of wolframite series minerals [(Fe,Mn)WO4], the main ore mineral for tungsten, by LA-SF-ICP-MS. Precision and accuracy of the protocol was intensively assessed using our newly developed well-characterized U–Pb wolframite reference material. The tungsten oxide interference on Hg and Pb was investigated in detail. The matrix effect between ferberite and hübnerite during laser ablation was thoroughly examined for wolframite series minerals with a different Mn/(Mn + Fe) ratio. The closure temperature of wolframite, with respect to the U–Pb system, was evaluated. The application of eleven wolframite samples, with ages from ∼1780 Ma to ∼26 Ma, robustly demonstrated the feasibility of our approach. Most studied wolframite series minerals yielded U–Pb concordant or subconcordant ages. Samples with a relatively high U content and negligible common Pb content typically had a 206Pb/238U age precision of ca. 1%. The new in situ data agree well with published cassiterite or wolframite ages from the same locations. LA-SF-ICP-MS, with the advantages of high sensitivity, rapidity, and relatively low cost, as well as moderate spatial resolution (i.e., 32 or 44 μm) that is sufficiently high to avoid sulfide inclusions, is the method of choice for in situ wolframite U–Pb microanalysis.

Description: The morphological difference of the northern equatorial ionization anomaly between theeastern Asian and American sectors is statistically studied with ground‐based total electron content datafrom 2000 to 2011. The intensity (Ic), latitudinal location (Lc), and occurrence time (Tc) of the daytimeequatorial ionization anomaly crest are derived from daytime peak total electron content in time‐latitudeplots. The main results are as follows.Lcin the two sectors exhibits an apparent difference, especially in solarminimum, during whichLcin the American sector shows an annual variation that is more poleward innorthern summer and more equatorward in northern winter, whileLcin the eastern Asian sector shows asemiannual variation that is more poleward around equinoxes and more equatorward around solstices.Ictends to be stronger in the eastern Asian sector than that in the American sector in all seasons, and thisdifference increases with the increase of the solarflux index.Tctends to be earlier in northern winter andlater in northern summer in both sectors and shows dependence on solar activity. We demonstrate thatthe seasonal variation ofLcin the American sector is not dominated by the ionospheric equatorial zonalelectricfield, and suggest that the difference ofLcbetween the two sectors is probably related to differentmeridional wind effects due to the displacement of geographic and magnetic equators. TheIcdifference isprobably related to the longitudinal wave number‐3 and‐4 structures driven by tidal forcing from the5lower atmosphere.

Description: To expand the newly developed ARM glasses as reference materials for in situ microanalysis of isotope ratios and iron oxidation state by a variety of techniques such as SIMS, LA-MC-ICP-MS and EPMA, we report Li-B-Si-O-Mg-Sr-Nd-Hf-Pb isotope data and Fe2+/ΣFe ratios for these glasses. The data were mainly obtained by TIMS, MC-ICP-MS, IR-MS and wet-chemistry colorimetric techniques. The quality of these data was cross-checked by comparing different techniques or by comparing the results from different laboratories using the same technique. All three glasses appear to be homogeneous with respect to the investigated isotope ratios (except for B in ARM-3) and Fe2+/ΣFe ratios at the scale of sampling volume and level of the analytical precision of each technique. The homogeneity of Li-B-O-Nd-Pb isotope ratios at the microscale (30–120 μm) was estimated using LA-MC-ICP-MS and SIMS techniques. We also present new EPMA major element data obtained using three different instruments for the glasses. The determination of reference values for the major elements and their uncertainties at the 95% confidence level closely followed ISO guidelines and the Certification Protocol of the International Association of Geoanalysts. The ARM glasses may be particularly useful as reference materials for in situ isotope ratio analysis.

Description: The North China Craton (NCC) is one of the oldest craton in the world. Since the Cenozoic, the NCC has experienced strong lithospheric thinning, accompanied by extensive tectonic deformation and volcanic activities. To better constrain the geodynamic processes and mechanisms of the lithospheric deformation, we used a linear damped least squares method to inverse simultaneously Rayleigh wave phase velocity and azimuthal anisotropy at periods of 10-80 s with teleseismic data recorded by 388 permanent stations in the NCC and its adjacent areas. The results reveal that the anomalies of Rayleigh wave phase velocity and azimuthal anisotropy are in good agreement with the tectonic domains in the NCC. The whole lithosphere of the Ordos block shows a high-phase velocity and rotated fast axis, which is related to the well-preserved thick lithospheric root and counterclockwise rotation of the Ordos block. The horizontal extension of the upwelling materials within the lower crust under the Datong volcano contributes to the regional rotation pattern of the fast axis direction of Rayleigh wave together with a distinct low-velocity anomaly. A NW-SE trending azimuthal anisotropy and a low-velocity anomaly originated from the Datong volcano at atop of the asthenosphere are revealed to be subparallel to the Zhangbo fault zone. This observation may be caused by the upwelling magma of the Datong volcano flow into the asthenosphere of the eastern NCC, which also provides new insights into the understanding of the lithospheric thinning of the eastern NCC.

Description: The ionospheric condition can be affected by the factors from above (solar flare, geomagnetic storm, etc.) and below (volcanoes, earthquake, severe weather disturbance, etc.). To distinguish these sources from ionospheric observations is important for understanding the ionospheric variability and is practically necessary for the ionospheric forecast. During the period from 21 Aug to 24, 2017, a tropical depression over the east of Luzon was formed, and with its moving along the west direction it intensified rapidly and soon developed a Super Typhoon named Hato. Hato made landfall in the south coast of Guangdong, China, on 23 Aug. 2017. During its landfall period, the ionospheric TEC in south China experienced large increase. It is noted that a weak geomagnetic storm also occurred in the landfall day. So, to determine the reasons of this large increase became very interesting. Based on TEC data derived from the dense distributed GNSS data near the landing area, the meteorological and geomagnetic storm data, the ionospheric variation are analyzed carefully to determine the source of this TEC enhancement, also to clarify this Typhoon’s effect on the ionosphere.

Description: 〉Regional atmospheric models struggle to maintain super-cooled liquid in mixed-phase clouds during polar cold-air outbreaks (CAOs). Previous studies focused on the parameterization of aerosol, microphysics and turbulence to understand the origin of this widespread model bias. This study investigates the role of macrophysics parameterizations in the simulation of mixed-phase clouds. We perform kilometer-scale simulations for all CAO cases observed during the Cold-Air Outbreaks in the Marine Boundary Layer Experiment (COMBLE) over Norway, for which continuous ground-based observations were collected over 6 months. A novel analysis is used that attributes the cloud-radiative errors to deficiencies in specific cloud regimes. We show that the macrophysics parameterization matters for cloud-radiative effects in CAOs, but that it is probably not the primary cause of the lack of liquid water in simulated mixed-phase clouds. Of all the macrophysics sensitivities explored in this study, the prognostic representation of both liquid and ice fraction shows most promise in increasing the liquid water path. A newly proposed hybrid macrophysics parameterization with prognostic frozen and diagnostic liquid cloud fraction reproduces some of the benefits of the prognostic scheme at reduced cost and complexity. The two-moment microphysics scheme in this study produces too large precipitation particles. Reducing the snow deposition rate decreases the precipitation particle sizes and largely improves the liquid water path. Simulations are less sensitive to reduced riming rates. This study confirms that uncertainties in mixed-phase microphysics are a major bottleneck to capturing observed cold-air outbreak cloud properties.

Description: Upper-ocean fronts are dynamically active features of the global ocean that have significant implications for air-sea interactions, vertical mass and heat transfers, stratification and phytoplankton production and export. Their small dimensions and short duration have limited our capacity of observing, modelling and understanding fully these processes and their impact. To address this challenge, five Saildrones - which are uncrewed platforms instrumented to measure the air-sea interface – were deployed during the EUREC4A-OA/ATOMIC field experiment in the Northwest Tropical Atlantic in winter 2020. This region is strongly affected by the outflow of the Amazon River, leading to the generation of fine-scale horizontal thermohaline gradients with the stirring of this freshwater input by large anticyclonic eddies. Very intense gradients, including at the smaller spatial scales, were measured. The coherence of temperature and salinity fronts was estimated by a wavelet transform analysis which revealed large-scale density fronts are primarily controlled by salinity but with increasing temperature-salinity coherence at the small scales range of the spectrum (O (0.1 km)) for strong gradients whereas they are poorly correlated for weaker fronts. Our study shows that processes such as the mixed layer depth, the diurnal cycle, and air-sea exchanges are strongly affected by these small-scale frontal regimes. The parallel and quasi synchronous tracks of a 4-Saildrone formation provide a detailed picture of the upper ocean vorticity, divergence, and strain from their ADCP current measurements. Overall the methodology developed could be extended on other datasets to assess the phenomenology of fine-scale structures in other dynamical regions.

Description: This paper designs an event-triggering based communication strategy for the global attitude synchronization of a network of rigid bodies. To overcome the topological constraint on the manifold SO(3), the quaternion-based hybrid control strategy is designed using a binary logic variable, relying on the relative measurements of adjacent rigid bodies, to determine the torque orientation. The Zeno-free distributed event-triggering strategies (ETSs) are designed combining with the reset of the binary logic variable to generate discrete communication instants, where only the corresponding parts of the control inputs are updated at those discrete instants. By assuming perfect knowledge of the rigid bodies' dynamics and considering uncertainties and/or exogenous disturbances simultaneously, nominal and robust cases are analyzed to ensure the global attitude synchronization, respectively. The effectiveness of the main results is demonstrated by considering the attitude synchronization of six miniature quadrotor prototypes.