A study of the relationship between cloud-to-ground lightning and precipitation in the convective weather system in China

International audienceIn this paper, the correlation between cloud-to-ground (CG) lightning and precipitation has been studied by making use of the data from weather radar, meteorological soundings, and a lightning location system that includes three direction finders about 40 km apart from each other in the Pingliang area of east Gansu province in P. R. China. We have studied the convective systems that developed during two cold front processes passing over the observation area, and found that the CG lightning can be an important factor in the precipitation estimation. The regression equation between the average precipitation intensity (R) and the number of CG lightning flashes (L) in the main precipitation period is R = 1.69 ln (L) - 0.27, and the correlation coefficient r is 0.86. The CG lightning flash rate can be used as an indicator of the formation and development of the convective weather system. Another more exhaustive precipitation estimation method has been developed by analyzing the temporal and spatial distributions of the precipitation relative to the location of the CG lightning flashes. Precipitation calculated from the CG lightning flashes is very useful, especially in regions with inadequate radar cover

Charge analysis on lightning discharges to the ground in Chinese inland plateau (close to Tibet)

International audienceSince the summer of 1996, scientists from China and Japan have conducted a joint observation of natural cloud-to-ground lightning discharges in the Zhongchuan area that is located close to Qinghai-Xizang (Tibet) Plateau, China. It has been found that the long-duration of intracloud discharge processes, just before the first return stroke, lasted more than 120 ms for 85% of cloud-to-ground flashes in this area, with a mean duration of 189.7 ms and a maximum of 300 ms. We present the results of charge sources neutralized by four ground flashes and two intracloud discharge processes, just before the first return stroke, by using the data from a 5-site slow antenna network synchronized by GPS with 1 µs time resolution. The result shows that the altitudes of the neutralized negative charge for three negative ground flashes were between 2.7 to 5.4 km above the ground, while that of neutralized positive charges for one positive ground flash and one continuing current process were at about 2.0 km above the ground. The comparison with radar echo showed that the negative discharges initiated in the region greater than 20 dBZ or near the edge of the region with intense echoes greater than 40 dBZ, while positive discharge initiated in the weak echo region.Key words: Meterology and atmospheric dynamics (atmospheric electricity; convective processes; lightning) <p style="line-height: 20px;"

Stromatoporoids from a Middle Devonian reef in South China and their palaeoecological implication

Supplementary file (518.3 kB) is available online at: https://www.app.pan.pl/archive/published/SOM/app67-Huang_etal_SOM.pdf .Copyright © 2022 J. Huang et al. Stromatoporoids are the major constructors of a Givetian (Middle Devonian) fossil reef in shallow marine facies, in the Jiwozhai Member of the Dushan Formation, at Dahekou, near Dushan, Guizhou Province, South China. Stromatoporoids, together with other reef building and dwelling components (rugose corals, tabulates, chaetetids and others), form a high diversity community, making the Jiwozhai reef a palaeobiodiversity hotspot. In this study 11 species belonging to nine genera and four orders are identified, including Gerronostromaria grossum (Clathrodictyida), Pseudotrupetostroma porosum, and Salairella buecheliensis (Stromatoporida), Clathrocoilona spissa, Stictostroma saginatum, and Synthetostroma actinostromoides (Stromatoporellida) and ?Habrostroma laminosum, Parallelopora sp., Stachyodes costulata, Stachyodes fasciculata and Stachyodes sp. (Syringostromatida). Among them, Clathrocoilona spissa and Gerronostromaria grossum are the most abundant stromatoporoid taxa. Stromatoporoid growth form, size, substrate and growth interruption are considered to be key autecological parameters to evaluate their growth behaviour and contribution in reef formation. Skeletons of laminar Clathrocoilona spissa are commonly smaller (up to 40 mm in basal dimension and less than 2 mm in thickness) than other stromatoporoid taxa and frequently encrusted on other organisms. In contrast, Gerronostromaria grossum dominates the assemblage, with its larger laminar growth form (up to 500 mm in basal dimension and 40 mm in thickness) expanding both on bioclastic and clay-rich micritic substrate and shows repeated growth interruptions, altogether evidence that this taxon was resilient to environmental pressure and may have pioneered the reef development. The variation of growth preference among stromatoporoid taxa therefore indicates a different growth strategy of each stromatoporoid in this reef environment.Chinese Academy of Sciences (XDB26000000); National Natural Science Foundation of China (grant No. 41772004)

Estimation of aerosol complex refractive indices for both fine and coarse modes simultaneously based on AERONET remote sensing products

Climate change assessment, especially model evaluation, requires a better understanding of complex refractive indices (CRIs) of atmospheric aerosols – separately for both fine and coarse modes. However, the widely used aerosol CRI obtained by the global Aerosol Robotic Network (AERONET) corresponds to total-column aerosol particles without separation for fine and coarse modes. This paper establishes a method to separate CRIs of fine and coarse particles based on AERONET volume particle size distribution (VPSD), aerosol optical depth (AOD) and absorbing AOD (AAOD). The method consists of two steps. First a multimodal log-normal distribution that best approximates the AERONET VPSD is found. Then the fine and coarse mode CRIs are found by iterative fitting of AERONET AODs to Mie calculations. The numerical experiment shows good performance for typical water-soluble, biomass burning and dust aerosol types, and the estimated uncertainties on the retrieved sub-mode CRIs are about 0.11 (real part) and 78 % (imaginary part). The 1-year measurements at the AERONET Beijing site are processed, and we obtain CRIs of 1.48–0.010i (imaginary part at 440 nm is 0.012) for fine mode particles and 1.49–0.004i (imaginary part at 440 nm is 0.007) for coarse mode particles, for the period of 2014–2015. Our results also suggest that both fine and coarse aerosol mode CRIs have distinct seasonal characteristics; in particular, CRIs of fine particles in winter season are significantly higher than summer due to possible anthropogenic influences

1D slipped stacking microribbon-like crystals based on 6,13-dicyanopentacene for ambipolar charge transport

Featuring small charge transport scattering, mesoscale size, and easy fabrication, one-dimensional self-assembled micro/nanomaterials (1D-MNMs) based on organic π-conjugated systems can be facilely incorporated into integrated microcircuits. Although tremendous progress has been made in 1D-MNMs based on p- or n-channel organic semiconductors, examples of lD-MNMs based on ambipolar organic semiconductors are scarce. Herein, we achieved a novel 1D-MNM based on 6,13-dicyanopentacene (DCP) with a 1D slipped stacking motif using the physical vapor transport method. The DCP-based 1D-MNM showed outstanding, well-balanced ambipolar charge transport with electron and hole mobilities of up to 0.34 and 0.38 cm2 V−1 s−1, respectively, which are among the best ambipolar transport characteristics of 1D-MNMs. Furthermore, a complementary inverter based on the ambipolar 1D-MNM of DCP was also constructed with a gain of up to 7, indicating potential application in organic logic circuits

Extensive marine anoxia associated with the Late Devonian Hangenberg Crisis

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record The global Hangenberg Crisis near the Devonian-Carboniferous boundary (DCB) represents one of the major Phanerozoic mass extinction events, which shaped the roots of modern vertebrate biodiversity. Marine anoxia has been cited as the proximate kill mechanism for this event. However, the detailed timing, duration, and extent of global marine redox chemistry changes across this critical interval remain controversial because most of the studies to date only constrain changes in local or regional redox chemistry. Thus, opinions on the significance of anoxia as a kill mechanism are variable—from anoxia being a primary driver to being relatively unimportant. In this study, we explore the evolution of global marine redox chemistry using U isotopes of marine limestones. The δ238U trends at Long'an section in South China document systematic oscillations with three negative shifts punctuated by two positive events in between. The magnitude of the δ238U oscillations implies that the sediments do not record contemporaneous seawater with a constant offset at all times. The lack of covariation between δ238U data and diagenetic indicators (e.g., Mn and Sr contents, Mn/Sr ratio, δ18O) suggests that the δ238U trends are not produced by the same post-depositional diagenetic processes. Instead, trace-metal enrichments suggest that more reducing conditions prevailed during the deposition of the two positive events. We present plausible model scenarios that fit the observed δ238U trends in the context of redox-sensitive trace metal data suggesting marine anoxia expanded in the latest Devonian oceans to cover >5% of the continental shelf seafloor area. The rapid expansion of marine anoxia coincident with the onset of the Hangenberg Crisis supports marine anoxia as an important kill mechanism. Biogeochemical modeling of the coupled C-P-U cycles suggests that intensified continental weathering, for example, assisted by the spread of seed plants with deeper root systems at this time, could have triggered expansion of marine anoxia and other global changes (e.g., positive excursion in δ13Ccarb and decrease in sea surface temperature) in the latest Devonian. The anoxic event is inferred to have been transient as climatic cooling would have reduced weathering fluxes.Natural Environment Research Council (NERC

Synergistic effect of quinary molten salts and Ruthenium catalyst for high-power-density Lithium-carbon dioxide cell

With a recent increase in interest in metal-gas batteries, the lithium-carbon dioxide cell has attracted considerable attention because of its extraordinary carbon dioxide-capture ability during the discharge process and its potential application as a power source for Mars exploration. However, owing to the stable lithium carbonate discharge product, the cell enables operation only at low current densities, which significantly limits the application of lithium-carbon dioxide batteries and effective carbon dioxide-capture cells. Here, we investigate a high-performance lithium-carbon dioxide cell using a quinary molten salt electrolyte and ruthenium nanoparticles on the carbon cathode. The nitrate-based molten salt electrolyte allows us to observe the enhanced carbon dioxide-capture rate and the reduced discharge-charge over-potential gap with that of conventional lithium-carbon dioxide cells. Furthermore, owing to the ruthernium catalyst, the cell sustains its performance over more than 300 cycles at a current density of 10.0Ag(-1) and exhibits a peak power density of 33.4mWcm(-2). Lithium-carbon dioxide cells are challenging due to the sluggish electron transfer in the Lithium carbonate in aprotic electrolyte. Here, the authors report synergistic effect of molten salt electrolyte and Ruthenium catalyst to enhance the electrochemical performance of Lithium-carbon dioxide batterie