Synoptic-scale potential vorticity intrusion over northeastern China during winter and its influence on surface air temperature

A regional potential vorticity (PV) intrusion (PVI) (RPVI) index, defined as the sum of the numbers of grids containing PVI within a certain area for each day, is used to reflect the day-to-day PVI variability over northeastern China during winter from 1979 to 2016. The synoptic-scale PVI variations and resultant surface air temperature (SAT) anomalies are identified by comparing the high and low RPVI index cases. In high (low) RPVI cases, significantly strong positive (negative) PV anomalies are found in the stratospheric midlatitudes, which intrude downward mostly within 90°–110°E into the upper troposphere to reach around 300 hPa and extend eastward to the east of 120°E, forcing an anomalous cyclonic (anticyclonic) circulation in the middle and lower troposphere over East Asia, with the anomalous northerlies (southerlies) of the forced lower-tropospheric cyclone (anticyclone) leading to significant negative (positive) SAT anomalies of less (greater) than −0.9°C (0.9°C), especially over northeastern China. In the stratosphere, the positive (negative) midlatitude PV anomalies over northern China are actually associated with a weakening (strengthening) of the polar vortex over the Eurasian continent for the high (low) RPVI cases, resulting mostly from positive (negative) barotropic vorticity anomalies associated with static stability due to the meridional shear of anomalous zonal winds on the southern side of the anomalous Eurasian anticyclone (cyclone)

Circulation anomalies in the mid–high latitudes responsible for the extremely hot summer of 2018 over northeast Asia

This study investigated the contributions of mid–high-latitude circulation anomalies to the extremely hot summer (July and August; JA) of 2018 over Northeast Asia (NEA). The JA-mean surface air temperature in 2018 was 1.2°C higher than that of the 1979–2018 climatology, with the amplitude of such an anomaly almost doubling the interannual standard deviation, making 2018 the hottest year during the analysis period 1979–2018. The abnormal warming over NEA was caused by a local positive geopotential height anomaly reaching strongest intensity in JA 2018. Further investigation suggested that the upper-tropospheric circulation anomalies over northern Europe and the Caspian Sea were crucial to forming this NEA circulation anomaly through initiating downstream wave trains. Particularly, the geopotential heights over these two regions were concurrently at their highest in JA 2018, and therefore jointly contributed to the profound circulation anomaly over NEA and the hottest summer on record. Due to these two teleconnection patterns, the temperature anomalies in NEA are closely related to those in both northern Europe and the Caspian Sea, where the similarly extreme warming also happened in 2018

Extreme heatwave over Eastern China in summer 2022: the role of three oceans and local soil moisture feedback

Eastern China experienced persistent regional extreme heatwaves in the summer of 2022, with disparate spatial features and formation mechanisms in different months. We quantitatively assessed the relative contributions of three oceans, i.e. tropical Indian Ocean and Pacific and North Atlantic, and the local soil moisture–temperature feedback using linear regression. The results showed that the monthly mean atmospheric circulation anomalies failed to explain the extreme heatwave in June 2022. The combined contribution of the tropical Indo-Pacific and North Atlantic sea surface temperature anomalies (SSTAs), together with the local soil moisture–temperature feedback, explaining approximately 10% of the temperature anomalies. In July, the tropical Indo-Pacific SSTAs promoted anomalous atmospheric circulation and extreme heat via meridional circulation originating in the Maritime Continent, accounting for approximately 10% of the temperature anomalies, with North Atlantic SSTAs contributing the same percentage by a mid-latitude steady Rossby wave. Local soil moisture–temperature feedback accounted for 42% of the anomalies. The tropical Indo-Pacific SSTAs produced a strong western North Pacific anticyclone in August, but their direct contribution to the temperature anomalies was negligible. The North Atlantic SSTAs contributed 9% of the total via the mid-latitude steady Rossby wave. Local soil moisture–temperature feedback contributed 66%, suggesting that the July heatwave and drought exerted a significant impact on the subsequent August extreme heatwave. Global warming has greatly facilitated extreme heatwaves, accounting for about 30%–40% of these events in summer 2022. These results also suggest that the climatic effects of tropical Indo-Pacific and North Atlantic SSTAs on Eastern China are evident in the month-to-month variation in summer. Our results thus contribute to the understanding and prediction of extreme heatwaves in Eastern China

Particle Size Distribution Effects on the Strength Characteristic of Cemented Paste Backfill

It is of great significance, for economic, environmental and security reasons, to investigate the strength characteristic of underground cemented paste backfill (CPB). Consequently, an ultrasonic test, uniaxial and triaxial compression experiment, and acoustic emission (AE) monitoring were carried out on CPB, for which the particles satisfied Talbot gradation. The homogeneity of CPB specimens was evaluated by ultrasonic pulse velocity (UPV). The stress–strain behavior and AE characteristic of CPB specimens under different Talbot indices and confining pressures were investigated. The effects of the particle size distribution and the confining pressure on the peak strength of CPB were analyzed. The strength parameter model of CPB under the coupled influence of the particle size distribution and the confining pressure was constructed based on the Mohr–Coulomb strength criterion. The results show that the peak strength of CPB is positively linear with confining pressure, however, the relationship between its strength parameters and the Talbot index can be characterized by a quadratic polynomial function. This suggests that there is an optimal gradation of particles reflected in the maximum strength of CPB

The Intra-Seasonal Oscillation of Precipitation δ<SUP>18</SUP>O Over the Asian Equatorial and Monsoon Regions

International audienceWater isotopes-climate correlations are used to reconstruct paleoclimate from various natural archives. Intra-seasonal oscillation is one of the major atmospheric patterns that modulate the ratio of precipitation isotope in low latitudes, yet their spatial and temporal distribution patterns are unclear. Here we presented a detailed analysis of how the intra-seasonal oscillations (MJO, Madden-Julian Oscillation, and BSISO, Boreal Summer Intra-seasonal Oscillation) modulate precipitation δ18O and vapor δ18O over the Asian monsoon region and the equatorial region. This analysis found consistent intra-seasonal variations between the ISO and rain δ18O. We interpret it as the ISO regulating the active and inactive convective systems on the regional scale, leading to the intra-seasonal oscillations in precipitation δ18O, with amplitudes from 4‰ up to 15‰. The MJO (BSISO) leads to eastward (northeastward) propagation of δ18O intra-seasonal oscillations in the Asian equatorial (monsoon) region, coinciding with the spatial patterns of OLR oscillations, reflecting the response of precipitation/vapor δ18O to the oscillation of large-scale convective activity or accumulated depletion of regional precipitation. We proved that the amplitudes of intra-seasonal variation of precipitation δ18O are comparable to seasonal variations, and both of them are the main patterns for precipitation δ18O in study regions. Our results are conducive to the accurate interpretation of δ18O in climate proxies such as precipitation, ice cores, tree cellulose, cave stalagmites, et al. on the intra-seasonal scale in this region

Self-assembling epitaxial growth of a single crystalline CoFe2O4 nanopillar array via dual-target pulsed laser deposition

Magnetic nanopillars are promising for a variety of technological applications, though the template-free fabrication of magnetic nanopillar arrays with good crystallinity and uniform distribution remains a substantial challenge. Herein, we report successful fabrication of a regular array of CoFe2O4 (CFO) nanopillars using an elaborately designed dual-target pulsed laser deposition (PLD) process, which exhibit a truncated pyramid surface with consistent size and orientation as well as uniform distribution. Detailed X-ray diffraction, scanning transmission electron microscopy and X-ray photoelectron spectroscopy demonstrate the high quality nature of the CFO nanopillars, while vibrating sample magnetometer and magnetic force microscopy studies confirm their room temperature magnetism. This dual-target PLD process takes advantage of BiFeO3 decomposition, and the subsequent formation of CFO nanopillars requires no template, giving us a powerful technique to prepare oxide nanopillars with desired composition and functional properties