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The influence and mechanism of volcanic eruptions on decadal megadroughts over eastern China during the last millennium were investigated using a control (CTRL) and five volcanic eruption sensitivity experiments (VOLC) from the Community Earth System Model (CESM) Last Millennium Ensemble (LME) archive. The decadal megadroughts associated with the failures of the East Asian summer monsoon (EASM) are associated with a meridional tripole of sea surface temperature anomalies (SSTAs) in the western Pacific from the equator to high latitudes, suggestive of a decadal-scale internal mode of variability that emerges from empirical orthogonal function (EOF) analysis. Composite analyses further showed that, on interannual time scales, within a decade after an eruption the megadrought was first enhanced but then weakened, due to the change from an El Niño state to a La Niña state. The impacts of volcanic eruptions on the magnitudes of megadroughts are superposed on internal variability. Therefore, the evolution of decadal megadroughts coinciding with strong volcanic eruptions demonstrate that the impacts of internal variability and external forcing can combine to influence hydroclimate.

Climate signals associated with 11-year sunspot cycle have been extensively studied in various regions of the northern hemisphere, but the precise mechanisms remain elusive. Asian winter monsoon (AWM) is the most powerful circulation system on the Earth, yet its relationship with the 11-year solar cycle has not been explored. Here the response of AWM to the 11-year solar forcing is explored by analysis of numerical experiment results obtained from the Community Earth System Model-Last Millennium Ensemble (CESM-LME) modeling project. We show that a strong 11-year solar cycle can excite a resonant response of the intrinsic leading mode of the AWM variability, resulting in a significant signal of decadal variation. The leading mode, characterized by a warm Arctic and cold Siberia, responds to the maximum solar irradiance with a peculiar 3 to 4-year delay. We propose a new mechanism to explain this delayed response, in which the 11-year solar cycle affects the AWM via modulating Arctic sea ice variation during the preceding summer. At the peak of the accumulative solar irradiance (i.e., 4 years after the maximum solar irradiance), the Arctic sea ice concentration reaches a minimum over the Barents–Kara Sea region accompanied by an Arctic sea surface warming, which then persists into the following winter, causing Arctic high-pressure extend to the Ural mountain region, which enhances Siberian High and causes a bitter winter over the northern Asia.

Silanes and organophosphorus compounds have been widely used in the field of corrosion inhibition. Herein, two corrosion inhibitors containing multiple phosphate groups and different silane groups, namely, 1,3-bis{3-[N-(1-phosphonatediethyl)-isopropyl] aminopropyl}-1,1,3,3-tetramethyldisiloxane (BPIAT) and N,N-di-methylenephosphonate-aminopropyl dimethyl silanol (DMADS), were designed and their corrosion inhibition properties on the iron surface in 0.5 M H2SO4 solution were characterized by polarization curves and electrochemical impedance spectroscopy (EIS) at 25 °C. In order to further analyze the corrosion mechanism thoroughly, three organophosphorus compounds without silane groups, namely, Hexamethylene-diamine tetra(methylene phosphonic acid) (HDTMPA), (ethylenedinitrilo)-tetra methylene phosphonic acid (EDTMP), and diethyl 1-decylphosphonate (DDP), were also investigated. The electrochemical experimental results reveal that five corrosion inhibitors are mixed type inhibitors and the adsorption process obeys Langmuir isotherm, and the corrosion inhibition efficiency of BPIAT and DPSD is significantly higher than that of HDTMPA, EDTMP and DDP. A new corrosion inhibition mechanism was proposed by comparing the corrosion inhibition performance of five corrosion inhibitors. The corrosion inhibitors are absorbed on the iron surface by Fe-O-P covalent bonds and Van Der Waals’ force. Simultaneously, the Si-O-Si structure is conducive to the improvement of the corrosion inhibition efficiency.

Changes in land cover and dust emission may significantly influence the Northern Hemisphere land monsoon precipitation (NHLMP), but observations are too short to fully evaluate their impacts. The G ...

The impact of northern high-latitude volcanic (NHV) eruptions on El Niño–Southern Oscillation (ENSO) is investigated based on ensemble simulations with the Community Earth System Model. The seasonality of the atmospheric circulation influences the NHV aerosol dispersion, causing stronger (weaker) Northern Hemisphere cooling after the January and April (July and October) eruptions. ENSO’s response is found to be more dependent on NHV eruption seasons than that on tropical eruption seasons. The January eruption causes an El Niño in an eruption year [year (0) hereafter] while an El Niño occurs in year (1) after the October eruption. No significant El Niño occurs after the April (July) eruption. A diagnostic analysis reveals that these El Niños’ developments are attributed to the positive zonal, meridional advective, and thermocline feedbacks, triggered by the western Pacific westerly anomalies. The anomalous North Pacific cyclone (NPC) and Asian monsoon are key systems to excite anomalous westerlies, which are caused by the NHV-induced midlatitude cooling and Eurasian continent–North Pacific thermal contrast. After the January eruption, the anomalous NPC develops in early summer and connects with a weakened Asian summer monsoon, which excites anomalous westerlies over the Indo-western Pacific, activating the Bjerknes feedback. For the October eruption, the anomalous NPC and enhanced East Asian winter monsoon bring cold air to the Maritime Continent and warm the subtropical central North Pacific through surface heat flux exchange, exciting the westerly anomalies. These results suggest that the strong dependence on the seasonal timing of NHV should be a critical element of data–model comparisons.

Statistical evidence suggests that solar activity may affect the atmospheric circulation over East Asia (EA), but the way in which the 11-yr solar radiation cycle affects the East Asian summer monsoon (EASM) remains unexplained. Based on one control experiment and four solar-only forcing experiments performed during the Community Earth System Model–Last Millennium Ensemble (CESM-LME) model project, we explore the potential impacts of the 11-yr solar cycle on EASM variability and the physical processes through which solar forcing influences EASM decadal variability. The model results show that the warm season [May–September (MJJAS)] mean precipitation over EA exhibits significant decadal variation with a “northern wet–southern dry” pattern during peak years in the strong 11-yr solar cycle epoch (AD 900–1285), which is in contrast to the absence of decadal signals during the weak 11-yr solar cycle epoch (AD 1400–1535). For the four-member ensemble averaged solar-only forcing experiment, the summer mean precipitation over northern EA is significantly correlated with the solar forcing (r = 0.414, n = 68, p < 0.05) on a decadal time scale during the strong cycle epoch, whereas there is no statistical link between the EASM and solar activity during the weak cycle epoch (r = 0.002, n = 24). A strong, 11-yr solar cycle is also shown to excite an anomalous sea surface temperature (SST) pattern that resembles a cool Pacific decadal oscillation (PDO) phase, which has a significant 11-yr periodicity. The associated anomalous North Pacific anticyclone dominates the entire extratropical North Pacific and enhances the southerly monsoon over EA, which results in abundant rainfall over northern EA. We argue that the 11-yr solar cycle affects the EASM decadal variation through excitation of a coupled decadal mode in the Asia–North Pacific region.

Significance The variability of the Asian summer monsoon (ASM) is important for the functioning of ecological and societal systems at regional to continental scales, but the long-term evolution and interannual variability of this system is not well understood. Here, we present a stable isotope–based reconstruction of ASM variability covering 4680 BCE to 2011 CE. Superimposed on a gradual drying trend, a rapid drop in mean annual precipitation (>40%) toward persistently drier conditions occurred in ∼1675 BCE. This megadrought caused regional forest deterioration and enhanced aeolian activity affecting Chinese ecosystems. We argue that this abrupt aridification starting ∼2000 BCE triggered waves of human migration and societal transformation in northern China, which contributed to the alteration of spatial pattern of ancient civilizations., Asian summer monsoon (ASM) variability and its long-term ecological and societal impacts extending back to Neolithic times are poorly understood due to a lack of high-resolution climate proxy data. Here, we present a precisely dated and well-calibrated tree-ring stable isotope chronology from the Tibetan Plateau with 1- to 5-y resolution that reflects high- to low-frequency ASM variability from 4680 BCE to 2011 CE. Superimposed on a persistent drying trend since the mid-Holocene, a rapid decrease in moisture availability between ∼2000 and ∼1500 BCE caused a dry hydroclimatic regime from ∼1675 to ∼1185 BCE, with mean precipitation estimated at 42 ± 4% and 5 ± 2% lower than during the mid-Holocene and the instrumental period, respectively. This second-millennium–BCE megadrought marks the mid-to late Holocene transition, during which regional forests declined and enhanced aeolian activity affected northern Chinese ecosystems. We argue that this abrupt aridification starting ∼2000 BCE contributed to the shift of Neolithic cultures in northern China and likely triggered human migration and societal transformation.

The upper-level jet stream, a narrow band of maximum wind speed in the mid-latitude westerlies, exerts a considerable influence on the global climate by modulating the transport and distribution of momentum, heat and moisture. In this study by using four high-resolution models in the Paleoclimate Modelling Intercomparison Project phase 3, the changes of position and intensity of the northern hemisphere westerly jet at 200 hPa in summer during the mid-Holocene (MH), as well as the related mechanisms, are investigated. The four models show similar performance on the westerly jet. At the hemispheric scale, the simulated westerly jet has a poleward shift during the MH compared to the preindustrial period. The warming in arctic and cooling in the tropics during the MH are caused by the orbital changes of the earth and the precipitation changes, and it could lead to the weakened meridional temperature gradient and pressure gradient, which might account for the poleward shift of the westerly jet from the thermodynamic perspective. From the dynamic perspective, two maximum centers of eddy kinetic energy are simulated over the North Pacific and North Atlantic with the north deviation, which could cause the northward movement of the westerly jet. The weakening of the jet stream is associated with the change of the Hadley cell and the meridional temperature gradient. The largest weakening is over the Pacific Ocean where both the dynamic and the thermodynamic processes have weakening effects. The smallest weakening is over the Atlantic Ocean, and it is induced by the offset effects of dynamic processes and thermodynamic processes. The weakening over the Eurasia is mainly caused by the dynamic processes.

Characterization of the tensile mechanical behaviors of rocks under dynamic loads is of great significance for the practical engineering. However, thus far, its micromechanics have rarely been studied. This paper micromechanically investigated the compression-induced tensile mechanical behaviors of the crystalline rock using the grain-based model (GBM) by universal distinct element code (UDEC). Results showed that the crystalline rock has the rate- and heterogeneity-dependency of tensile behaviors. Essentially, dynamic Brazilian tensile strength increased in a linear manner as the loading rate increased. With the size distribution and morphology of grain-scale heterogeneity weakened, it increased, and this trend was obviously enhanced as the loading rate increased. Additionally, the rate-dependent characteristic became strong with the grain heterogeneity weakened. The grain heterogeneity prominently affected the stress distribution inside the synthetic crystalline rock, especially in the mixed compression and tension zone. Due to heterogeneity, there were tensile stress concentrations (TSCs) in the sample which could favor microcracking and strength weakening of the sample. As the grain heterogeneity weakened or the loading rate increased, the magnitude of the TSC had a decreasing trend and there was a transition from the sharp TSC to the smooth tensile stress distribution zone. The progressive failure of the crystalline rock was notably influenced by the loading rate, which mainly represented the formation of the crushing zone adjacent to two loading points. Our results are meaningful for the practical engineering such as underground protection works from stress waves.

The shear strength characteristics of rock masses containing non-persistent discontinuities are strongly affected by discontinuities and rock bridges. The linear Jennings criterion cannot reflect the nonlinear mechanical behavior during progressive failure of rock masses with non-persistent discontinuities. In this study, a new nonlinear shear strength criterion was developed. First of all, a series of shear test data about artificial rock mass samples were collected on the basis of the published literatures, and five types of samples were differentiated according to the positions of discontinuities. After that, a new nonlinear shear strength criterion was proposed by introducing two correction coefficients A and B into the basic form of the Jennings criterion, which could correct the weight of the cohesion and the internal friction coefficient of rock bridges respectively. Then, the new criterion was determined by fitting the basic form of the Jennings criterion with the laboratory data. It was found that the parameters A and B had a nonlinear exponential and negative exponential relation with the connectivity rate respectively. It indicated that both the cohesion and the internal friction coefficient estimated by the new criterion were superior to those estimated by the Jennings criterion. Compared with the linear Jennings criterion, the new nonlinear shear strength criterion had a better applicability.

This paper microscopically investigated progressive failure characteristics of brittle rock under high-strain-rate compression using the bonded particle model (BPM). We considered the intact sample and the flawed sample loaded by split Hopkinson pressure bar respectively. Results showed that the progressive failure characteristics of the brittle rock highly depended on the strain rate. The intact sample first experienced in microcracking, then crack coalescing, and finally splitting into fragments. The total number of the micro cracks, the proportion of the shear cracks, the number of fragments and the strain at the peak stress all increased with the increasing strain rate. Also, a transition existed for the failure of the brittle rock from brittleness to ductility as the strain rate increased. For the flawed sample, the microcracking initiation position and the types of the formed macro cracks were influenced by the flaw angle in the initial stage. However, propagation of these early-formed macro cracks were prohibited in the later stages. New micro cracks were produced and then coalesced into diagonal macro cracks which could all form &lsquo, X&rsquo, shape failure configuration regardless of the incline angle of the flaw. We explored micromechanics on progressive failure characteristics of the brittle rock under dynamic loads.

The Ming Dynasty Mega-drought (MDMD) (1637-1643) occurred at the end of Ming Dynasty and is the severest drought event in China in the last millennium. This unprecedented drought contributed signif...

Industrial application of superhydrophobic surfaces is often hindered by complicated process and sophisticated machines. A facile wet etching method (sandblast, HCl and sandblast/HCl) with vapor deposition of PFDS (1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane) was applied to fabricate superhydrophobic surface of heat-resistant steel used for vane. The coating component, surface morphology and surface roughness parameters of sample were observed by attenuated total reflectance Fourier transform infrared spectroscopy, scanning electron microscopy and atomic force microscopy. Static water contact angle (WCA) of samples with and without PFDS coating was measured by contact angle goniometer. The results showed that WCA values of polished, sandblast, HCl and sandblast/HCl-etched samples are 98°, 97°, 100° and 101°, respectively, and increase to 112°, 148°, 151° and 154° after vapor deposition of PFDS. The sandblast/HCl-etched sample with PFDS coating shows higher superhydrophobicity because of very large surface roughness and lotus protrusion-like structure. The superhydrophobicity of this fabricated surface has no obvious change after 38 cycles of the film adhesion test, indicating excellent durability.

Using an ensemble of nine El Nino/Southern Oscillation (ENSO) reconstructed proxies and volcano eruption proxies for the past 1500 years, this study shows that a significant La Nina state emerges in the second year (year (2) hereafter) after large tropical volcanic eruptions. The reasons for the development of La Nina are investigated using the Community Earth System Model (CESM). In the volcanic eruption experiment (Vol), a robust La Nina signal occurs in year (2), resembling the proxy records. The eastward positioning of the western North Pacific anomalous anticyclone (WNPAC) in Vol plays a critical role in the advanced decay of year (2) warming and the strong intensification of cooling in the equatorial eastern Pacific. The enhanced easterlies located on the southern edge of the WNPAC can stimulate consecutive oceanic upwelling Kelvin waves, shallowing the thermocline in the eastern Pacific, thereby resulting in a greater cooling rate by the enhanced thermocline feedback and cold zonal advection. Over the equatorial eastern Pacific, the reduced shortwave radiation contributes to the advanced decay of warming, while the upward latent heat flux augments the strong intensification of the cooling. Essentially, the eastward positioning of the WNPAC is a result of the volcanic forcing. The volcanic effect cools the maritime continent more than its adjacent oceans, thus pushing convective anomalies eastward during year (1). This induces vertical thermal advection and upward surface latent heat flux, thereby suppressing the development of warm Sea Surface Temperature over the central-western Pacific and causing the eastward positioning of the WNPAC in Vol.

The influences of natural forcings (i.e. solar radiation and volcanic aerosol) and anthropogenic forcings (i.e. greenhouse gases) on the tropical Pacific zonal sea-surface temperature (SST) gradient are investigated through numerical sensitivity experiments, forced by natural forcing, anthropogenic forcing, or full forcing (both natural and anthropogenic forcing) using the Community Earth System Model (CESM) over the past two millennia. Under full forcing, during the present warming period (PWP; 1901–1999), the Pacific SST shows a larger warming over the tropical Pacific region than the subtropical Pacific region. This pattern is composed of an El Nino-like SST gradient (due to the greenhouse gas forcing) and a La Nina-like SST gradient (due to natural forcing). Two sensitivity experiments, the PWP under greenhouse gas forcing and the medieval warming period (MWP; 751–1250) under natural forcing, were used to examine the mechanisms. The results showed that under the greenhouse gas forcing, the larger warming over the eastern tropical Pacific is induced by an increased surface net heat flux, which is mainly caused by short-wave radiation and long-wave radiation. Under natural forcing, a larger warming is induced over the western tropical Pacific by changes in the ocean vertical heat transportation, caused by surface wind anomalies.

Based on the high-resolution observed daily precipitation data, three characteristic regions over eastern China are first defined through the rotated empirical orthogonal function. Then, the relationship between summer (June-July-August) extreme precipitation across the three characteristic regions of eastern China and the South Asian High (SAH) is examined to determine how the northwest-southeast movement and area (magnitude) of SAH influence the summer extreme precipitation across eastern China. When the South Asian High is located anomalously northwest, there is more extreme precipitation over the northern part of eastern China but less extreme precipitation over the Jiang-Huai River Basin. When the SAH intensifies, there is more extreme precipitation over the Jiang-Huai River Basin. The mechanisms are that under the conditions of anomalously northwestward displacements, the positive geopotential anomalies over central Asia induce a deep barotropic Korean High through a Rossby wave train, resulting in more water vapor transportation to eastern China with more convergence over the northern part of eastern China located at the northwestern edge of the Korean High but with a divergence over the Jiang-Huai River Basin. When the SAH intensifies, accompanied by an enhanced and westward extended western Pacific subtropical High, the convergence over the Jiang-Huai River Basin increases with enhanced water vapor transportation due to the confluence of warm and cold advections. These mechanisms are achieved through shifts toward the high tail (low tail) of the daily precipitation cumulative distributions of these two regions and finally increases (decreases) in the occurrence of extreme precipitation.

The spatial patterns of global temperature and precipitation changes, as well as corresponding large-scale circulation patterns during the latter part of the 9th and 5th millennia BP (4800–4500 versus 4500–4000 BP and 9200–8800 versus 8800–8000 BP) are compared through a group of transient simulations using the Community Climate System Model version 3 (CCSM3). Both periods are characterized by significant sea surface temperature (SST) decreases over the North Atlantic, south of Iceland. Temperatures were also colder across the Northern Hemisphere but warmer in the Southern Hemisphere. Significant precipitation decreases are seen over most of the Northern Hemisphere, especially over Eurasia and the Asian monsoon regions, indicating a weaker summer monsoon. Large precipitation anomalies over northern South America and adjacent ocean regions are related to a southward displacement of the Intertropical Convergence Zone (ITCZ) in that region. Climate changes in the late 9th millennium BP (the “8.2 ka event”) are widely considered to have been caused by a large freshwater discharge into the northern Atlantic, which is confirmed in a meltwater forcing sensitivity experiment, but this was not the cause of changes occurring between the early and latter halves of the 5th millennium BP. Model simulations suggest that a combination of factors, led by long-term changes in insolation, drove a steady decline in SSTs across the North Atlantic and a reduction in the North Atlantic Meridional Overturning Circulation (AMOC), over the past 4500 years, with associated teleconnections across the globe, leading to drought in some areas. Multi-century-scale fluctuations in SSTs and AMOC strength were superimposed on this decline. This helps explain the onset of neoglaciation around 5000–4500 BP, followed by a series of neoglacial advances and retreats during recent millennia. The “4.2 ka BP Event” appears to have been one of several late Holocene multi-century fluctuations that were embedded in the long-term, low-frequency change in climate that occurred after ∼4.8 ka. Whether these multi-century fluctuations were a response to internal centennial-scale ocean–atmosphere variability or external forcing (such as explosive volcanic eruptions and associated feedbacks) or a combination of such conditions is not known and requires further study.

The variability and mechanisms of multi-decadal megadroughts over eastern China during the last millennium were investigated using a control, full-forcing, and four sensitivity experiments from the Community Earth System Model (CESM) Last Millennium Ensemble (LME) archive. The model simulated megadroughts have comparable magnitudes and durations with those derived from reconstructed proxy data, although the megadroughts are not temporally synchronous. In all experiments, the megadroughts exhibit similar spatial structures, corresponding to a weakening of the East Asia summer monsoon (EASM) and a strengthening of the East Asia winter monsoon (EAWM). The results show that internal climate variability within the coupled climate system plays an essential role in triggering megadroughts, while different external forcings may contribute to persistence and modify the anomaly patterns of megadroughts. A pattern of meridional tripolar (warm-cold-warm) sea surface temperature (SST) anomalies in the western Pacific stretching from the equator to high latitude is responsible for the EASM weakening and EAWM strengthening. The weakening of the EASM and strengthening of the EAWM are essentially caused by negative SST anomalies over the northwestern Pacific and positive SST anomalies over the equatorial western Pacific, which are associated with a La Ni&ntilde, a-like SST gradient across the tropical Pacific. The external forcings prolong the megadroughts through maintenance of the meridional tripolar SST anomalies and enlarge the megadrought spatial extent by magnifying the meridional tripolar SST anomalies.

Aims To improve the comprehensive performances of a one-part room temperature vulcanized silicone rubber(RTV-1 SiR), Nano-SiO2 particles are employed as the reinforcing agent. Materials and Methods The SiO2/RTV-1 SiR composite is prepared using PDMS, ND42, D-60 and HMDS-modified SiO2 particles by mixing method. And then, the mechanical and electrical properties, including shear strength, tensile strength, hardness Shore A and volume resistivity, are investigated using experimental method. Results The addition of nano-SiO2 particles can improve the properties of the SiO2/RTV-1 SiR composite in different degrees. And, the incorporation of 25∼30 phr nano-SiO2 particles is found to be reasonable for silicone rubber composite with the best comprehensive performances. Conclusions The significant improvement of mechanical properties and electrical insulation of SiO2 may be contributed to the addition of modified nano-SiO2 particles. Additionally, the excellent comprehensive performances of SiO2/RTV-1 SiR composite guarantee a potential applications as electrical-insulating adhesives.

A kind of fluorine-containing acrylic copolymer was synthesized via a two steps of fluorine modification route. A hydrophobic fluorine-containing acrylic polyurethane coating was prepared with the synthesized fluorine-containing acrylic copolymer and trimer of hexamethylene diisocyanate curing agent. The fluorine-containing acrylic polyurethane coating was employed as the topcoat, while a kind of epoxy coating was used as the primer. The failure behavior of the acrylic polyurethane and epoxy composite coatings in 3.5 wt.% NaCl aqueous solution and 5 wt.% salt spray environments were studied. Chemical structure of the copolymer was confirmed by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance ( 19 F NMR). Glass-transition temperature (Tg) of the copolymer was determined with differential scanning calorimetry (DSC). The surface and cross-section morphologies of the coatings before and after failure test were explored via digital microscopy and field emission scanning electron microscopy (FESEM). The electrochemical impedance spectroscopy (EIS) was employed to analyze the coating corrosion resistance during the failure process. X-ray photoelectron spectroscopy (XPS) was used to provide insights into the chemical compositions of the coating surface. The results showed that the fluorine-containing copolymer and the corresponding coating were prepared as expected. The fluorine-containing acrylic polyurethane and epoxy composite coatings failed much faster in the salt spray environment than that in the NaCl aqueous solution. The different environment resulted in different surface chemical compositions.

In this study, the role of AD 1258 Samalas mega volcanic eruption in the summer hydroclimate change over Europe and the corresponding mechanisms are investigated through multi-member ensemble climate simulation experiments based on the Community Earth System Model (CESM). The results show that the CESM simulations are consistent with the reconstructed Palmer Drought Severity Index (PDSI) and the historical records of European climate. Europe experiences significant summer cooling in the first three years after the Samalas mega volcanic eruption, peaking at &minus, 3.61 &deg, C, &minus, 4.02 &deg, C, and &minus, 3.21 &deg, C in year 1 over the whole Europe, Southern Europe, and Northern Europe, respectively. The summer surface air temperature (SAT, &deg, C) changes over the European continent are mainly due to the direct weakening of shortwave solar radiation induced by volcanic aerosol. The summer precipitation over the European continent shows an obvious dipole distribution characteristic of north-south reverse phase. The precipitation increases up to 0.42 mm/d in year 1 over Southern Europe, while it decreases by &minus, 0.28 mm/d in year 1 over Northern Europe, respectively. Both simulations and reconstructions show that the centers with the strongest increase in precipitation have always been located in the Balkans and Apennine peninsulas along the Mediterranean coast over Southern Europe, and the centers with the strongest precipitation reduction are mainly located in the British Isles and Scandinavia over northwestern Europe. The negative response of North Atlantic Oscillation (NAO) with significant positive sea level pressure (SLP) anomaly in the north and negative SLP anomaly in the south is excited in summer. The low tropospheric wind anomaly caused by the negative phase of NAO in summer affects the water vapor transport to Europe, resulting in the distribution pattern of summer precipitation in Europe, which is drying in the north and wetting in the south. The knowledge gained from this study is crucial to better understand and predict the potential impacts of single mega volcanic eruption on the future summer hydroclimate change in Europe.

A rock mass often contains joints filled with a viscoelastic medium of which seismic response is significant to geophysical exploration and seismic engineering design. Using the propagator matrix method, an analytical model was established to characterize the seismic response of viscoelastic filled joints. Stress wave propagation through a single joint highly depended on the water content and thickness of the filling as well as the frequency and incident angle of the incident wave. The increase in the water content enhanced the viscosity (depicted by quality factor) of the filled joint, which could promote equivalent joint stiffness and energy dissipation with double effects on stress wave propagation. There existed multiple reflections when the stress wave propagated through a set of filled joints. The dimensionless joint spacing was the main controlling factor in the seismic response of the multiple filled joints. As it increased, the transmission coefficient first increased, then it decreased instead, and at last it basically kept invariant. The effect of multiple reflections was weakened by increasing the water content, which further influenced the variation of the transmission coefficient. The water content of the joint filling should be paid more attention in practical applications.

In this study, the influences on persistent droughts over Eastern China from tropical volcanic eruptions with three categories of magnitudes, i.e., 25 Tg, 50 Tg, and 100 Tg, were investigated through three groups of volcanic sensitivity experiments based on the Community Earth System Model (CESM). The results showed that, the 25 Tg tropical volcanic eruptions are too weak to significantly influence the regional precipitation changes over Eastern China, while the 50 Tg tropical volcanic eruptions can strongly intensify droughts and prolong the drought conditions for about five years. Both the extension and intensification of the drought conditions induced by 100 Tg tropical volcanic eruption are the largest among the three sensitivity experiments. These drought conditions are mainly caused by the weakened East Asia Summer Monsoon (EASM), and their extension and intensification depend on the strength of the volcanic eruptions. The intensities of weakened EASMs after volcanic eruptions are associated with the distinct ocean&ndash, land thermal contrast after eruptions. The ocean&ndash, land thermal contrast is the largest after the 100 Tg tropical volcanic eruptions, while it is much weaker after the 25 Tg volcanic eruptions. The durations of drought extensions are determined by the recovery rates of the West Pacific Subtropical High (WPSH), which are associated with the magnitudes of the volcanic eruptions.

Superhydrophobic surfaces have attracted much interest in the research on surface roughness and application of abrasion resistance, corrosion resistance and anti-icing performance. In this work, a superhydrophobic surface has been fabricated by vapor deposition of PFDS (1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane) on surface of sandblasted/HCl-etched heat-resistant steel. The HCl-etched surface had petal effect showing good superhydrophobicity with apparent contact angle of 153° and high-water adhesion. The sandblasted/HCl-etched surface had lotus effect exhibiting excellent superhydrophobic properties with apparent contact angle of 159° and low-water adhesion. The coating on the heat-resistant steel also had outstanding abrasion resistance withstanding 300 cm abrasion distance on sandpaper. The coating remained superhydrophobicity after immersing in the H2SO4 solution with various PH values. Simultaneously, the fatigue life of heat-resistant steel was improved significantly by sandblasted/HCl-etched and coated with PFDS.

The historical and future relationships between two major patterns of large-scale climate variability, the North Atlantic Oscillation (NAO) and the Pacific/North America pattern (PNA), and the regional winter temperature and precipitation over the eastern United States were systemically evaluated by using 17 general circulation models (GCMs) from the Coupled Model Intercomparison Project phase 5. Empirical orthogonal function analysis was used to define the NAO and PNA. The observed spatial patterns of NAO and PNA can be reproduced by all the GCMs with slight differences in locations of the centers of action and their average magnitudes. For the correlations with regional winter temperature and precipitation over the eastern US, GCMs perform best in capturing the relationships between the NAO and winter temperature, and between the PNA and winter temperature and precipitation. The differences between the observed and simulated relationships are mainly due to displacements of the simulated NAO and PNA centers of action and differences in their magnitudes. In simulations of the future, both NAO and PNA magnitudes increase, with uncertainties related to the model response and emission scenarios. When assessing the influences of future NAO/PNA changes on regional winter temperature, it is found that the main factors are related to changes in the magnitude of the NAO Azores center and total NAO magnitude, and the longitude of the PNA center over northwestern North America, total PNA magnitude, and the magnitude of the PNA center over the southeastern US.

Asian summer monsoon (ASM) precipitation is the primary water resource for agriculture in many Asian countries that have experienced rapid economic growth in recent decades, thus implying the necessity for further investigations on both the internal variability of the ASM and the influence of external factors on the ASM. Using long-term high-resolution (0.5° × 0.5°) observed precipitation data, contrary to previous studies on inter-annual timescale, we showed that over the last 110 years, volcanic eruptions have influenced ASM variations on an inter-decadal timescale via teleconnections with the Atlantic Multi-decadal Oscillation (AMO). This relationship was also confirmed by Coupled Model Intercomparison Program Phase 5 (CMIP5) model simulations. During the active volcanic eruption periods (1901–1935 and 1963–1993), significantly lower ASM precipitation was observed compared with that during the inactive volcanic eruption period (1936–1962). We found that during active volcanic eruption periods, which correspond to a negative AMO state, there is an anomalously weakened Walker circulation over the tropical Pacific that transports less moisture to the ASM region and subsequently reduces ASM precipitation. This new finding may help improve decadal predictions of future changes in the ASM.

We review some recent work regarding climatic changes in selected mountain regions, with particular attention to the tropics and the American Cordillera. Key aspects of climatic variability and trends in these regions are the amplification of surface warming trends with height, and the strong modulation of temperature trends by tropical sea surface temperature, largely controlled by changes in El Nino–Southern Oscillation on multiple time scales. Corollary aspects of these climate trends include the increase in a critical plant growth temperature threshold, a rise in the freezing level surface, and the possibility of enhanced subtropical drying. Anthropogenic global warming projections indicate a strong likelihood for enhancement of these observed changes.