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Atmospheric rivers (ARs), intrusions of warm and moist air, can effectively drive weather extremes over the Arctic and trigger subsequent impact on sea ice and climate. What controls the observed multi-decadal Arctic AR trends remains unclear. Here, using multiple sources of observations and model experiments, we find that, contrary to the uniform positive trend in climate simulations, the observed Arctic AR frequency increases by twice as much over the Atlantic sector compared to the Pacific sector in 1981-2021. This discrepancy can be reconciled by the observed positive-to-negative phase shift of Interdecadal Pacific Oscillation (IPO) and the negative-to-positive phase shift of Atlantic Multidecadal Oscillation (AMO), which increase and reduce Arctic ARs over the Atlantic and Pacific sectors, respectively. Removing the influence of the IPO and AMO can reduce the projection uncertainties in near-future Arctic AR trends by about 24%, which is important for constraining projection of Arctic warming and the timing of an ice-free Arctic.

We present a comprehensive analysis of Arctic surface energy budget (SEB) components during atmospheric river (AR) events identified by integrated water vapor transport exceeding the monthly 85th percentile climatological threshold in 3-hourly ERA5 reanalysis data from January 1980 to December 2015. Analysis of average anomalies in SEB components, net SEB, and the overall AR contribution to the total seasonal SEB reveals clear seasonality and distinct land – sea – sea ice contrast patterns. Over the sea ice-covered central Arctic Ocean, ARs significantly impact net SEB, inducing substantial surface warming in fall, winter, and spring, primarily driven by large anomalies in surface downward longwave radiation. We find that ARs make a substantial relative contribution to the mean SEB in spring (32 %), exceeding their corresponding occurrence frequency (11 %). However, in other seasons, ARs contribute relatively less to the mean SEB than their frequency, indicating a diminished role compared to their occurrence frequency. Over sub-polar oceans, ARs have the most substantial positive impact on net SEB in cold seasons, mainly attributed to significant positive turbulent heat flux anomalies, with a maximum contribution to the mean SEB in spring averaging 65 %. In summer, ARs induce negative impacts on net SEB, primarily due to reduced shortwave radiation from increased cloud cover during AR events. Over continents, ARs generate smaller absolute impacts on net SEB but contribute significantly to the mean SEB in cold seasons, far surpassing their corresponding frequency, highlighting their crucial role in determining the net SEB over continents during cold seasons. Greenland, especially western Greenland, exhibits significant downward longwave radiation anomalies associated with ARs, which drive large net SEB anomalies and contribute >54 % to mean SEB, and induce amplified surface warming year-round. This holds significance for melt events, particularly during summer. This study quantifies the role of ARs on surface energy budget, contributing to our understanding of the Arctic warming and sea ice decline in ongoing Arctic amplification. [ABSTRACT FROM AUTHOR]

Improving the soil structure and fertility of saline–alkali land is a major issue in establishing a sustainable agro-ecosystem. To explore the potential of different straw returning in improving saline–alkaline land, we utilized native saline–alkaline soil (SCK), wheat straw-returned saline–alkaline soil (SXM) and rapeseed straw-returned saline–alkaline soil (SYC) as our research objects. Soil physicochemical properties, fungal community structure and diversity of saline–alkaline soils were investigated in different treatments at 0–10 cm, 10–20 cm and 20–30 cm soil depths. The results showed that SXM and SYC reduced soil pH and total salinity but increased soil organic matter, alkali-hydrolyzable nitrogen, available phosphorus, total potassium, etc., and the enhancement effect of SYC was more significant. The total salinity of the 0–10 cm SCK soil layer was much higher than that of the 10–30 cm soil layers. Fungal diversity and abundance were similar in different soil layers in the same treatment. SXM and SYC soil had higher fungal diversity and abundance than SCK. At the genus level, Plectosphaerella, Mortierella and Ascomycota were the dominant groups of fungal communities in SXM and SYC. The fungal diversity and abundance in SXM and SYC soils were higher than in SCK soils. Correlation network analysis of fungal communities with environmental factors showed that organic matter, alkali-hydrolyzable nitrogen and available phosphorus were the main environmental factors for the structural composition of fungal communities of Mortierella, Typhula, Wickerhamomyces, Trichosporon and Candida. In summary, straw returning to the field played an effective role in improving saline–alkaline land, improving soil fertility, affecting the structure and diversity of the fungal community and changing the interactions between microorganisms. [ABSTRACT FROM AUTHOR]

An extreme warming event near the North Pole, with temperature rising above 0 ℃, was observed in late December 2015. This specific event has been attributed to cyclones and their associated moisture intrusions. However, little is known about the characteristics and drivers of similar events in the historical record. Here, using data from ERA5, we study these winter extreme warming events with temperature above 0 ℃ over the high Arctic (poleward of 80° N) occurred during 1980–2021. In ERA5, such extreme events can only be found over the Atlantic sector. They occur rarely, with a seasonal occurrence frequency less than one over most of the regions. Furthermore, even when occurring, they tend to be short-lived, with the majority of the events lasting for less than a day. By examining their surface energy budget, we found that these events transition with increasing latitude from a regime dominated by turbulent heat flux into the one dominated by downward longwave radiation. Blockings over the northern Eurasia are identified as a key ingredient in driving these events, as they can effectively deflect the eastward propagating cyclones poleward, leading to intense moisture and heat intrusions into the high Arctic. Using an atmospheric river (AR) detection algorithm, the roles of ARs in driving these events are explicitly quantified. The importance of ARs in inducing these events increases with latitude. Poleward of about 83° N, ARs are the direct driver for 100 % of these events, corroborating the indispensable roles ARs played in driving these events. Over the past four decades, both the frequency, duration, and magnitude of these events have been increasing significantly. As the Arctic continues to warm, these events are likely to increase in both frequency, duration and magnitude, with great implications for the local sea ice, hydrological cycle and ecosystem. [ABSTRACT FROM AUTHOR]

Water-induced crystallization of polycarbonate (PC) was investigated in water-saturated supercritical C[O.sub.2] (scC[O.sub.2]) in the range of 80-160°C and 12-20 MPa, with the help of differential scanning calorimetry and wide-angle X-ray diffraction. Compared with pure scC[O.sub.2], the enhanced plasticizing effect of water-saturated scC[O.sub.2] reduced the energy-barrier for the motion of polymer chains, hence increased the crystallization rate of PC, and reduced the pressure threshold for crystallization from 14 to 12 MPa. On the other hand, the presence of water did not affect the thermodynamics of PC crystallization in scC[O.sub.2]. A 3D-diagram was established to show the relationship between crystallization and solubility parameter of mixed supercritical fluid at different temperatures and pressures. The results show clearly that the PC has a wider range of crystallization temperature and pressure in water-saturated scC[O.sub.2] than in pure scC[O.sub.2], mostly because the addition of water increased significantly the solubility parameter of mixed supercritical fluid, and decreased the difference in solubility parameter between PC and water-saturated scC[O.sub.2]. POLYM. ENG. SCI., 47:1338-1343, 2007. © 2007 Society of Plastics Engineers, INTRODUCTION Bisphenol-A polycarbonate (PC) is a semicrystalline polymer characterized by a very low crystallization rate, because of its chain rigidity and the difficulty in transforming into a crystalline structure. At [...]

In this paper, a general lumped circuit modeling method is proposed to describe the conducted electromagnetic interference (EMI) coupling mechanism for the switching power converters. The EMI characteristics of the converters can be analytically deduced from a circuit theoretical viewpoint. The shunt and series impedance insertion method is introduced to identify the differential-mode (DM) and common-mode (CM) noise impedances and voltage sources. The procedure of parameters estimation for the noise models comprises several simple measurements and is convenient to be implemented. Experimental illustrations are also included to verify the validity of the proposed method. Comparison between the measured and predicted results shows that the EMI modeling method can provide adequate prediction of the EMI feature for power-switching converters. Index Terms--Conducted electromagnetic interference (EMI), lumped circuit models, noise sources and impedances, power-switching converters.

An improved and simplified electromagnetic interference (EMI) modeling method based on multiple slope approximation of device-switching transitions for EMI analysis of power converters is presented. The traditional noise source modeling method, which uses single slope for rise and fall transition, is studied, and the criteria for reasonable modeling in the frequency range is analyzed. The turn-on and turn-off dynamics are investigated by dividing the nonlinear transitions into several stages based on an insulated gate bipolar transistor (IGBT) behavior circuit model. Real device-switching voltage and current waveforms are approximated by piece-wise linear lines and modeled by multiple dv/dt and di/dt slopes. The predicted EMI spectra suggest that high-frequency EMI noise is modeled with an acceptable accuracy. The proposed method was verified experimentally for a dc-dc buck converter. Index Terms--Electromagnetic interference (EMI), insulated gate bipolar transistors (IGBTs), modeling, power converters, spectral analysis.

On the basis of the new idea of electric power integration, a novel stand-alone dual stator-winding induction generator (DWIG) system is built. In this generator, there are two sets of windings to be embedded in the stator slots. One, referred to as the 12-phase power winding, supplies power to the dc load via a 12-phase bridge rectifier, and the other, called the 3-phase excitation winding, is connected to a pulsewidth modulation (PWM) voltage source static excitation regulator (SER). A solid iron squirrel cage rotor is suitable for high speed generation. Experiments and simulations show the ac capacitors can reduce the inductance of rectifier loads and help to reduce the capacitance of the SER. A simple control methodology based on stator voltage orientation (SVO) is presented to regulate the output voltage of the 12-phase bridge rectifier in this paper. Moreover, the electric energy quality and the relative influence factors are studied by detailed experiments and analyses. The proposed system is especially suitable for self contained electrical systems, such as those found on electric vehicles, ships, and aircraft, where high performance and compact size are essential. Index Terms--AC capacitors, dual stator-winding induction generator, electric energy quality, electric power integration, high speed generation, 12-phase bridge rectifier, self-contained, stator voltage orientation.