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How much the observed long-term variability of tropical cyclone (TC) activity is due to anthropogenic global warming (GW) or internal climate variability remains unclear, limiting the confidence in projected future change in TC activity. Here, the relative contributions of GW and the Interdecadal Pacific Oscillation (IPO) to the long-term variability of TC track density (TCTD) over the North Pacific (NP) are quantified on the basis of statistical analyses and climate model simulations. Results show that historical GW mainly reduced (increased) TCTD over the western (eastern) NP, while the positive (negative) IPO corresponds to a NP basin-wide increase (decrease) in TCTD except in some coastal regions. The IPO has a much greater impact on TCTD over the western NP than GW, while the IPO and GW impacts are about equal over the eastern NP during 1960-2019. These findings have important implications for projecting future TC activity over the NP.

The interdecadal variability of tropical cyclone precipitation (TCP) over the western North Pacific (WNP) has not been thoroughly explored in previous studies. Here, we show that the TCP variations are modulated by both the Atlantic Multidecadal Oscillation (AMO) and Interdecadal Pacific Oscillation (IPO) as evidenced by reanalysis data and model experiments. A clustering analysis of tropical cyclone tracks shows that the AMO dominates a dipole pattern of TCP anomalies in the South China Sea and along the coastal eastern China. Meanwhile, the IPO dominates TCP over the southeastern WNP. Further analyses show that the AMO, particularly its extratropical component, affects TCP over the WNP by triggering an eastward‐propagating Rossby‐wave train, resulting in a pair of anomalous gyres over the WNP. Contrastly, the IPO modulates TCP by stimulating tropical circulation anomalies via the tropical pathway. These findings shed light on improving near‐term TCP forecast and its regional influence on East Asia. Plain Language Summary: Tropical cyclone precipitation (TCP) is a topic of great concern owing to its destructive nature. Here, we find that TCP over the western North Pacific (WNP) exhibits significantly interdecadal variability and regional characteristics, a departure from the previous studies focusing on the entire WNP. The Atlantic Multidecadal Oscillation (AMO) mainly causes a dipole response of decadal changes in TCP over the South China Sea and coastal eastern China. Moreover, the AMO primarily affects TCP over the sub‐regional WNP through the extra‐tropical pathway by exciting a Rossby wave train. On the other hand, the Interdecadal Pacific Oscillation (IPO) predominantly affects TCP over the southeastern part of the WNP through the tropical pathway, inducing significant circulation anomalies over the tropical WNP. These findings offer valuable insights for future research and forecasting of TCP. Key Points: The Atlantic Multidecadal Oscillation (AMO) contributes to the dipole pattern of interdecadal tropical cyclone precipitation (TCP) anomalies over the South China Sea and coastal eastern ChinaThe AMO affects TCP by triggering a westerly jet‐guided Rossby‐wave train via the extra‐tropical pathwayThe Interdecadal Pacific Oscillation dominates the TCP anomalies over the southeastern part of western North Pacific by modulating tropical circulation anomalies [ABSTRACT FROM AUTHOR]

Tropical cyclones (TCs) are among the most devastating natural hazards for coastal regions, and their response to human activities has broad socio-economic relevance. So far, how TC responds to climate change mitigation remains unknown, complicating the design of adaptation policies. Using net-zero and negative carbon emission experiments, we reveal a robust hemisphere-asymmetric hysteretic TC response to CO2 reduction. During the decarbonization phase, the Northern Hemisphere TC frequency continues to decrease for several more decades, while the Southern Hemisphere oceans abruptly shifts to a stormier state, with the timescales depending on mitigation details. Such systematic changes are largely attributed to the planetary-scale reorganization of vertical wind shear and midlevel upward motion associated with the hysteretic southward migration of the Intertropical Convergence Zone, underpinned by the Atlantic Meridional Overturning Circulation and El Niño-like mean state changes. The hemispheric contrast in TC response suggests promising benefits for most of the world's population from human action to mitigate greenhouse gas warming, but it may also exacerbate regional socioeconomic disparities, for example by putting more pressure on small open-ocean island states in the Southern Hemisphere to adapt to TC risks. [ABSTRACT FROM AUTHOR]

Current coupled climate models contain large biases in simulating tropical cyclogenesis, reducing the confidence in tropical cyclone (TC) projection. In this study, we investigated the influence of sea surface temperature (SST) biases on TC genesis in the Coupled Model Intercomparison Project phase 6 simulations from 1979 to 2014. Positive TC genesis biases were found over the tropical central North Pacific (CNP) in most of climate models, including the high-resolution models. Compared to coupled models, TC genesis density (TCGD) simulations over CNP in uncoupled models forced by observational SST improved obviously. A warm SST bias over the tropical CNP in the coupled models is the main cause of TC genesis biases. The SST bias–induced diabatic heating leads to an anomalous Gill-type atmospheric circulation response, which contributes to a series of favorable environmental conditions for TC formation over the CNP. Numerical experiments were also performed with HiRAM to demonstrate the influence of SST biases on the TCGD simulation, further confirming our conclusion. The current results highlight the importance of improving TC simulation in state-of-the-art climate models by reducing SST simulation bias. [ABSTRACT FROM AUTHOR]

A prominent feature of the western North Pacific tropical cyclone genesis frequency (TCGF) anomaly in response to El Niño‐Southern Oscillation (ENSO) is a distinct west‐east dipole structure in the present‐day (PD) climate. Here, large ensemble high‐resolution simulations show that the current dipole may transform into a monopole under global warming (GW). In the PD climate, the ENSO‐induced dipole effect on TCGF is mainly observed in late autumn. However, GW accelerates this effect into the summer by amplifying atmospheric circulation anomalies. Consequently, this leads to a significant increase in the coastal TCGF during the development phase of El Niño under GW. Meanwhile, it weakens the anomalous anticyclonic circulation during late autumn, leading to an increase in coastal TCGF during the mature phase of El Niño, and vice versa. Therefore, the combined effect suggests a potential trend toward spatial homogenization during ENSO phases under GW. Plain Language Summary: El Niño‐Southern Oscillation (ENSO) typically has a dipole impact on tropical cyclone genesis frequency (TCGF) over the western North Pacific (WNP) in the current climate. During the warm phase of ENSO, there is a significant increase in TCGF over the southeastern part of the WNP (open‐sea region), but a decrease over its northwestern part (coastal region). The opposite pattern occurs during the cold phase of ENSO. However, under global warming (GW), this dipole pattern could transform into a basin‐uniform change in TCGF. In the present climate, ENSO primarily affects TCGF only over the open‐sea region during the summer (June to August) but causes a dipole pattern of TCGF anomalies in the autumn (September–November). The summer TCGF over the coastal region is less influenced by ENSO. Hence, the dipole pattern of TCGF anomalies from summer to autumn is mainly contributed by the anomaly in autumn TCGF over the coastal region. However, GW could extend the ENSO impact on coastal TCGF to summer. Therefore, the TCGF anomaly in summer offsets the opposite TCGF anomaly in autumn over the coastal region during the ENSO phase, resulting in a more consistent change in TCGF anomalies across the region under GW. Key Points: The dipole pattern of tropical cyclone genesis frequency (TCGF) during June–November in response to El Niño‐Southern Oscillation (ENSO) over the western North Pacific may transform into a monopole under global warming (GW)The present‐day dipole of TCGF anomaly is mainly observed in late‐autumn, while GW accelerates this impact to summerGW amplifies cyclonic (anticyclonic) circulation during warm (cold) ENSO phases, causing a basin‐uniform TCGF change [ABSTRACT FROM AUTHOR]

Sand and dust storm (SDS) weather has caused several severe hazards in many regions worldwide, e.g., environmental pollution, traffic disruptions, and human casualties. Widespread surveillance cameras show great potential for high spatiotemporal resolution SDS observation. This study explores the possibility of employing the surveillance camera as an alternative SDS monitor. Based on SDS image feature analysis, a Multi-Stream Attention-aware Convolutional Neural Network (MA-CNN), which learns SDS image features at different scales through a multi-stream structure and employs an attention mechanism to enhance the detection performance, is constructed for an accurate SDS observation task. Moreover, a dataset with 13,216 images was built to train and test the MA-CNN. Eighteen algorithms, including nine well-known deep learning models and their variants built on an attention mechanism, were used for comparison. The experimental results showed that the MA-CNN achieved an accuracy performance of 0.857 on the training dataset, while this value changed to 0.945, 0.919, and 0.953 in three different real-world scenarios, which is the optimal performance among the compared algorithms. Therefore, surveillance camera-based monitors can effectively observe the occurrence of SDS disasters and provide valuable supplements to existing SDS observation networks. [ABSTRACT FROM AUTHOR]

The June‐July Yangtze flooding in 1998 and 2020 drew incredible attention owing to the extreme precipitation events and devastating societal/economic damages. However, the quantitative estimation of the moisture transport mechanism is intensely discussed but still unresolved. Here we investigated two events from a unique perspective of Eulerian atmospheric water tracers that tries to explain the two events from model physics. The results showed that the moisture supplies from the Northwest Pacific decreased despite of different inducements, whereas the southwest summer monsoon (SWSM)‐related moisture supplies exhibited conspicuous enhancements in both events, suggesting that the SWSM‐related moisture supplies controlled the occurrence of Yangtze flooding. The physical processes of the two events were further compared. The 2020 flooding was more severe than the 1998 event, which was related to the stronger advective convergences and in‐stratus condensations of the SWSM‐related moisture. Plain Language Summary: In 1998 and 2020, the Yangtze River valley experienced extreme rainfalls during June–July. The associated atmospheric river was detected to be significantly enhanced by the moisture from the southwest summer monsoon‐related source regions (such as the Bay of Bengal, Arabian Sea, Tropical Indian Ocean, Indo‐China Peninsula, and India) in both events. On the contrary, the moisture supplies from the Northwest Pacific declined. These results suggested that the southwest summer monsoon‐related moisture supplies played vital roles in the formations of extreme rainfalls over the Yangtze River valley. Additionally, our study investigated the differences in the physical mechanisms of the two extreme rainfall events. The stronger advective transport and cloud processes forced more southwest summer monsoon‐related moisture to be converted into precipitation around the Yangtze River, ultimately leading to more severe flooding in 2020 than in 1998. Key Points: The southwest summer monsoon (SWSM)‐related moisture supplies regulate the emergence of the Yangtze flooding during June–JulyAlong with the flooding appearances, the moisture supplies from the Northwest Pacific to the Yangtze River valley decreaseStronger advective transport and in‐stratus condensations of the SWSM‐related moisture avail the larger flooding in 2020 than in 1998 [ABSTRACT FROM AUTHOR]

How future multiple tropical cyclone events (MTCEs) could change is crucial for effective risk management and ensuring human safety, however, it remains unclear. This study projects changes in MTCEs by 2050 in the major basins of the Northern Hemisphere using high‐resolution climate models. Results show a significant increase in the frequency and duration of MTCEs over the North Atlantic (NA), a notable decrease over the western North Pacific (WNP), and little change over the eastern North Pacific (ENP). The increase in MTCEs over the NA is concentrated in August–September, while the decrease over the WNP occurs in most months. In contrast, the ENP exhibits large yet insignificant seasonal variation, suggesting considerable uncertainty in this basin. Further analysis shows that mid‐level vertical motion dominates the MTCE changes over the WNP, while vertical wind shear contributes the most to the NA, which may be linked to future changes in tropical convection. Plain Language Summary: Multiple tropical cyclone (TC) events (MTCEs), that is two or more TCs simultaneously occurring in the same basin, pose great risks to human society. This study projects future changes in the MTCEs by 2050, showing a significant increase over the North Atlantic (NA) while a robust reduction over the western North Pacific (WNP). The future MTCEs over the eastern North Pacific (ENP) show little change relative to the present climate. The increase of MTCEs over the NA is concentrated in August–September, while the decrease over the WNP occurs nearly from April to November. In contrast, there is large yet insignificant seasonal variation over the ENP, which could lead to little change in annual MTCEs. Furthermore, these changes are primarily attributed to the changes in local large‐scale dynamic conditions associated with tropical convection in future decades. Key Points: The projection of future multiple tropical cyclone events (MTCEs) shows a decline in the western North Pacific (WNP) but a significant increase in the North Atlantic (NA)The mid‐level vertical motion dominates the MTCE changes over the WNP, while vertical wind shear is important for the NAFuture monthly MTCEs show large yet insignificant seasonal variation over the eastern North Pacific, causing little trend in annual MTCEs [ABSTRACT FROM AUTHOR]

El Niño-Southern Oscillation (ENSO) teleconnections exhibit a strong dependency on seasonally and intraseasonally varying mean states, leading to impactful short-term variations in regional climate. The North Atlantic Oscillation (NAO)-ENSO relation is a typical example, in that its phase relationship reverses systematically between the early and late winter. Here based on observations and an ensemble of atmosphere-only climate model simulations, we reveal that this NAO phase reversal occurs synchronously in early January, showing strong abruptness. We demonstrate that this abrupt NAO phase reversal is caused by the change in ENSO-induced Rossby wave-propagating direction from northeastward to southeastward over the northeastern North American region, which is largely governed by a climatological alteration of the local jet meridional shear. We also provide evidence that the North Atlantic intrinsic eddy–low-frequency flow feedback further amplifies the NAO responses. This ENSO-related abrupt NAO change offers an avenue for intraseasonal climate forecasting in the Euro-Atlantic region. [ABSTRACT FROM AUTHOR]

Global tropical cyclone (TC) genesis frequency (TCGF) has been documented to decrease or increase linearly in a changing climate. However, our numerical experiments show that the global TCGF exhibits a parabolic relation with spatio‐uniform climate changes in sea surface temperature (SST) from −15 K to 5 K relative to the present climate, with the peak in the 5 K‐cooler climate. The parabolic relation is found in all TC basins except the eastern North Pacific where TCGF keeps increasing with the changing climate. TCGF can be expressed as the product of the frequency of TC seeds and the TC survival rate (SR). Further analysis shows that this parabolic structure in the global TCGF depends on TC seeds rather than the TC SR. The TC SR exhibits an increasing trend with the SST increase, while TC seeds show a consistent change with TCGF, which might be linked to the changes in low‐level relative humidity. Plain Language Summary: It is a hot‐debated question as to how tropical cyclone (TC) genesis frequency (TCGF) would change under global warming. To address this problem, we examine the TCGF change in response to a simplified spatio‐uniform change of sea surface temperature (SST) from −15 K to 5 K relative to the present climate. The global TCGF begins to increase with the global SST increase from −15 K, reaches peak in the 5 K‐cooler climate, and subsequently decreases with further SST warming, forming a parabolic relation between the TCGF and the SST changes. Further, we find the parabolic relationship in all TC basins except the eastern North Pacific where the TCGF keeps increasing with SST changes. TCGF can be expressed as the product of the frequency of TC seeds and the TC survival rate (SR). Further analysis shows the TC SR cannot explain the global TCGF change, while the changes in frequency of TC seeds associated with the low‐level relative humidity contribute to the parabolic change of TCGF. Key Points: The global tropical cyclone (TC) genesis frequency (TCGF) in response to uniform sea surface temperature (SST) changes shows a parabolic relation with a peak under 5 K‐cooler climate than current climateThe parabolic relation was found in all TC basins except the eastern North Pacific where the TCGF keeps increasing with SST changesSuch a parabolic relation was attributed to the change in TC seed frequency [ABSTRACT FROM AUTHOR]

Near‐term prediction of tropical cyclone (TC) activity is of great importance to formulate the long‐term plans for mitigating the potential TC‐induced damages. Here, we introduce a multi‐timescale regression model of TC genesis frequency (TCGF), which includes contributions by three interannual modes (El Niño‐Southern Oscillation, sea surface temperature anomalies over the eastern Indian Ocean and tropical North Atlantic), two interdecadal modes (the Atlantic Multidecadal Oscillation and the Interdecadal Pacific Oscillation), and a global warming mode. The model is shown to be able to capture well the present‐day multi‐timescale changes in TCGF in the major TC basins in the Northern Hemisphere. By combining the model and 100‐member simulations by the Max Planck Institute Earth System Model, we predict a robust increase in TCGF over the eastern North Pacific, an insignificant increase over the western North Pacific, and little change over the North Atlantic during 2020–2030 relative to 2009–2019. Plain Language Summary: How tropical cyclone (TC) activity will change in the next decade or so is especially important for government policymakers. However, the field on TC activity is very much in its infancy. Here we predict the near‐term changes in TC genesis frequency (TCGF) in the three main TC basins in the Northern Hemisphere, namely the western North Pacific, the eastern North Pacific, and the North Atlantic, by combining a new multi‐timescale regression model and the state‐of‐the‐art climate model projections. This regression model is constructed based on six key climate factors on different time scales, and can well reproduce the present‐day TCGF change during 1960–2019. The model predicts a significant increase in TCGF over the eastern North Pacific while insignificant change over the other two basins in the next 10 years. Key Points: We have developed a multi‐timescale regression model to represent changes in tropical cyclone (TC) genesis frequency (TCGF)The model can capture well the present‐day multi‐timescale changes in TCGF in the major TC basins in the Northern HemisphereThe model is used to conduct near‐term prediction of TCGF in the Northern Hemisphere by combining climate model projections [ABSTRACT FROM AUTHOR]

Observational and climate model analysis showed that the anomalous sea surface temperature in the north tropical Atlantic (NTA) in boreal spring can trigger El Niño–Southern Oscillation (ENSO) in the subsequent winter. Similarly, the climate models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5) are known to reasonably simulate the NTA effect. Nevertheless, the strengths of the NTA effect on ENSO among the climate models are also diverse. In this light, we revisited the possible causes that contributed to the different NTA effects on ENSO in the CMIP5 climate models. We found that the strength of the NTA triggering ENSO in the climate model tended to be proportional to the intensity of the climatological subtropical North Pacific high system in boreal spring. The stronger climatological subtropical North Pacific high accompanied enhanced trade wind, precipitation reduction, and cold sea surface temperature over the subtropics. Under these conditions, the moist static energy feedback process, also known as the moist enthalpy advection mechanism, effectively operated around the Pacific intertropical convergence zone. That is, the NTA-induced signals in the subtropical North Pacific readily intruded into the deep tropical Pacific with the aid of the feedback processes, leading to an ENSO event. Consistent with the CMIP5 analysis results, the observed NTA effect on ENSO became stronger during the decades when the climatological North Pacific subtropical high intensified, underpinning the importance of climatology in the subtropical North Pacific in the NTA–ENSO connection. [ABSTRACT FROM AUTHOR]

Confidence and uncertainty issues of simulations were seldom evaluated in previous studies although the climate models are widely used. This study evaluates the performance of the CMIP6-HighResMIP simulations in presenting long-term variability of tropical cyclone (TC) genesis frequency (TCGF) and track density (TCTD) and quantifies the relative contributions of internal and external forcing to TC activities during the 1950–2014. There is overall poor model performance in simulating long-term changes in TC activities over the Northern Hemisphere, including interdecadal variabilities and long-term linear trends. The simulated long-term changes in TCGF and TCTD over the eastern North Pacific (ENP) in six high-resolution models show opposite characteristics to the observations. Moreover, most models cannot capture the variabilities of TCGF and TCTD over the western part of the western North Pacific (WNP) and northern part of the North Atlantic (NA). However, these models show a high degree of confidence in reproducing the interdecadal variabilities and linear trends of TCGF and TCTD over the eastern part of the WNP and the tropical NA. Quantitative evaluations further show that there are the opposite relative contributions of long-term climate variabilities to TCGF and TCTD changes over the ENP between the observations and the multimodel ensemble mean, followed by large model biases over the western WNP and the northern NA, but relatively consistent contributions over the southern NA and the Caribbean. These results help us cope with contrasting and consistent future TC changes among the model projections. Significance Statement: While climate models have been widely used to project future changes in tropical cyclone (TC) activity, few studies have examined to what extent we can trust these model projections. We used the CMIP6-HighResMIP simulations to quantify the model biases in presenting TC activity, and evaluate the relative contributions of internal and external forcing to TC activities. In general, the HighResMIP has large discrepancies in representing longer-term climate variability of TC activity. However, the models can capture well TC activity over the eastern part of the western North Pacific and tropical Atlantic, which is attributed to good performance of models in reproducing the relationship between long-term climate variabilities beyond interannual scale and TC activity. These results highlight confidence and uncertainty in future TC changes among the model projections. [ABSTRACT FROM AUTHOR]

A mild strategy for fabricating nanoporous silver (np-Ag) pieces was reported via preparation of Agâ€"Ga alloys in relatively low temperature and subsequent electrochemical dealloying in nitric acid (HNO3) aqueous solution. After selectively etching Ga out of the Agâ€"Ga alloy, a typical three-dimensional (3D) bicontinuous nanoporous structure with a pore size of ∼67.21â€"159.33 nm was observed. A series of studies have shown that the addition of sodium dodecyl sulfate (SDS) results in minimum pore size. The coarsen exponent (n) is 1.61, and the activation energy was calculated to be 27.04 kJ molâˆ'1. The ζ ′-AgGa alloy prepared at low temperature can be used as the precursor for the preparation of fine np-Ags, and this method provides a new strategy for the industrial production of dealloyed np-Ag. [ABSTRACT FROM AUTHOR]

The multi‐model ensemble mean sea surface temperature (SST) of CMIP5 models shows an El Niño‐like Pacific warming (PW) trend, contradictory with the observational result which manifests a La Niña‐like PW pattern. Here, we demonstrate that these two SST PWs coexist in the CMIP5 models and they are largely determined by the model's tropical Indo‐Pacific SST gradient. When the Pacific warms faster than the Indian Ocean (IO), the model tends to project an El Niño‐like PW pattern. In contrast, a La Niña‐like warming trend prevails if a more rapid IO warming is simulated. We suggest that the PW pattern in an individual model is nonstationary and may transform from a La Niña‐like to an El Niño‐like when its interbasin SST gradient changes with more robust warming in the Pacific, and vice versa. Our conclusions shed great light on the future SST PW pattern change projected by the coupled models. Plain Language Summary: Previous studies demonstrate that an El Niño‐like SST warming pattern prevails in a majority of CMIP5 models. But a La Niña‐like warming pattern is detected based on historical SST records. This inconsistency between the observations and model simulation triggers an intense debate in the climate community. In this study, we find that both El Niño‐like and La Niña‐like SST warming patterns can be identified in the CMIP5 model simulations. The warming pattern is largely determined by the SST gradient between the Indian and Pacific oceans. Distinct from previous studies, an El Niño‐like pattern in an individual model can shift to a La Niña‐like pattern when the Indian warming is stronger than the Pacific warming trend, and vice versa. Key Points: El Niño‐like and La Niña‐like Pacific sea surface temperature warming patterns coexist and are interchangeable in climate model projectionsThe tropical Pacific warming pattern is primarily determined by a zonal gradient in the Indo‐Pacific sea surface warmingThis Pacific warming pattern diversity sheds light on future sea surface temperature change under greenhouse gases concentrations [ABSTRACT FROM AUTHOR]

Numerous studies have demonstrated that the North Pacific Meridional Mode (NPMM) plays an important role in determining El Niño‐Southern Oscillation (ENSO) events in the following winter season. However, little attention has been given to significant differences among its spatial patterns. Here we show that the NPMM exhibits a large diversity in spatial patterns, leading to distinct impacts on ENSO. Based on objective clustering analysis, two distinct spatial patterns of NPMM are detected. Cluster 1 (C1) NPMM exhibits a strong sea surface temperature dipole over the subtropical eastern Pacific and midlatitude central Pacific whereas Cluster 2 (C2) features a dipole over the subtropical eastern Pacific and equatorial cold tongue region. We find that the C1 NPMM is strongly linked to following ENSO events while the C2 NPMM has no statistically significant relation. This gives new implications for ENSO dynamics and predictions. Key Points: The North Pacific Meridional Mode (NPMM) has strong spatial diversity that can be separated into two groupsThese two types of the spring NPMM have distinct impacts on ENSO events in the following winterWe suggest an optimal pattern of the spring NPMM for ENSO prediction [ABSTRACT FROM AUTHOR]

How future tropical cyclone (TC) activity could change under global warming is enormously important to society, which has been widely assessed using state‐of‐the‐art climate models. However, these models were predominantly based on projection of an El Niño‐like warming pattern. Recent studies suggested that a La Niña‐like warming pattern is also possible. Here we compare the responses of TC track density (TCTD) over the western North Pacific and North Atlantic to the two distinct global warming patterns. We find that the La Niña‐like warming pattern reduces western North Pacific TCTD except in the South China Sea and along China coast and increases NA TCTD, while the El Niño‐like warming pattern generally reduces TCTD in both basins. This is due to different responses of large‐scale dynamic/thermodynamic conditions to the distinct zonal sea surface temperature gradients associated with the two warming patterns. These results help better understand potential future change in TC tracks. Key Points: The La Niña‐like warming reduces (increases) TC track density in the main WNP (NA), while the El Niño‐like warming reduces it in two basinsThe different responses are due to the different tropical zonal SST gradients associated with the two warming patternsChina and North America would experience more landfalling TCs in La Niña‐like warming pattern than in El Niño‐like warming pattern [ABSTRACT FROM AUTHOR]

By conducting idealized experiments in a general circulation model (GCM) and in a toy theoretical model, we test the hypothesis that shallow convection (SC) is responsible for explaining why the boreal summer intraseasonal oscillation (BSISO) prefers propagating northward. Two simulations are performed using ECHAM4, with the control run using a standard detrainment rate of SC and the sensitivity run turning off the detrainment rate of SC. These two simulations display dramatically different BSISO characteristics. The control run simulates the realistic northward propagation (NP) of the BSISO, while the sensitivity run with little SC only simulates stationary signals. In the sensitivity run, the meridional asymmetries of vorticity and humidity fields are simulated under the monsoon vertical wind shear (VWS); thus, the frictional convergence can be excited to the north of the BSISO. However, the lack of SC makes the lower and middle troposphere very dry, which prohibits further development of deeper convection. A theoretical BSISO model is also constructed, and the result shows that SC is a key to convey the asymmetric vorticity effect to induce the BSISO to move northward. Thus, both the GCM and theoretical model results demonstrate the importance of SC in promoting the NP of the BSISO. [ABSTRACT FROM AUTHOR]

Intense tropical cyclones (TCs) formed over the western part of the western North Pacific (WWNP) pose greater coastal risk than those formed over the eastern part (EWNP). Here we show that the proportion of intense TCs relative to all TCs (PITC) locally formed over the WWNP west of 140°E has increased significantly by about 16% to 20%, or equivalently almost doubled, since the late 1970s. However, the PITC over the EWNP has experienced little change. This sharp west-east contrast is primarily driven by the La Niña-like sea surface temperature (SST) pattern in the Pacific, identified as the mega El Niño-Southern Oscillation (ENSO) in previous studies. It is shown that the strong warming in the WWNP has contributed greatly to the increased PITC. In the EWNP, the dynamical conditions associated with the intensified mega-ENSO play a vital opposite role in offsetting and even overweighting the effect of local SST warming. [ABSTRACT FROM AUTHOR]

The aims of this paper were studied bactericidal effect of the ultraviolet lamp on irradiation intensity, irradiation time and installation height. Three independent variables were set, such as irradiation intensity, irradiation time and installation height. By natural sedimentation method, the airborne bacteria were sampled before and after radiation of ultraviolet lamp, then the decay rates of airborne bacteria were calculated. The decontaminated efficiency were more than 40% when irradiation power of UV were 30w (42.5%) and 40w (60%). With the lengthen irradiation time, the better reduced rate of the airborne bacteria. The bactericidal effect of the ultraviolet lamps was in proportion to their irradiation intensity and in inverse proportion to their installation height. According to the actual circumstance of university cafeteria, the arrangement of ultraviolet lamp was that irradiation intensity was 40W, installation height was 2.0m, and irradiation time was 60min. [ABSTRACT FROM AUTHOR]

ABSTRACT Based on the daily outgoing long-wave radiation data of the National Oceanic and Atmospheric Administration from 1979 to 2012, we investigated the intensity changes of the 20- to 70-day boreal summer (June-September, JJAS) intraseasonal oscillation ( BSISO) and winter (December-February, DJF) intraseasonal oscillation, also known as the Madden-Julian Oscillation ( MJO). The results showed that the intensity of the BSISO has a significant intensifying trend during 1982-2009. On the other hand, little trend was found for boreal winter MJO during this period. The wavenumber-frequency analysis was applied to separate ISO into westward propagation and eastward propagation parts. The significant intensified trend was observed over tropical Indian Ocean for the eastward propagation BSISO. The weakened but not significant trend was observed over southern tropical Indian Ocean for the eastward propagation MJO. To gain insight into the different ISO characteristics, the tendencies of sea surface temperature ( SST) and the vertical shear of zonal wind were analysed. The results showed that in both seasons from 1982 to 2009, the global SST trends were similar, and thus they could not be used to explain the BSISO upward trend. However, lower tropospheric easterly shear in boreal summer over tropical Indian Ocean had a decreasing trend, while the easterly vertical shear over maritime continent was enhanced in winter. It is proposed that the reduced easterly vertical shear over tropical Indian Ocean favoured the amplification of the eastward propagating Kelvin wave, which led to the intensified eastward propagating BSISO. The enhanced easterly vertical shear over maritime continent might be unfavourable to the amplification of the eastward propagating Kelvin wave, but its impact was offset by the enhanced upward motion over maritime continent. As a result, there was little trend of the MJO in boreal winter. The above hypothesis was further verified by intermediate model results. [ABSTRACT FROM AUTHOR]

A mild strategy for fabricating nanoporous silver (np-Ag) pieces was reported via preparation of Ag-Ga alloys in relatively low temperature and subsequent electrochemical dealloying in nitric acid (HNO 3 ) aqueous solution. After selectively etching Ga out of the Ag-Ga alloy, a typical three-dimensional (3D) bicontinuous nanoporous structure with a pore size of ∼67.21-159.33 nm was observed. A series of studies have shown that the addition of sodium dodecyl sulfate (SDS) results in minimum pore size. The coarsen exponent ( n ) is 1.61, and the activation energy was calculated to be 27.04 kJ mol -1 . The ζ '-AgGa alloy prepared at low temperature can be used as the precursor for the preparation of fine np-Ags, and this method provides a new strategy for the industrial production of dealloyed np-Ag., (© 2022 IOP Publishing Ltd.)

The recent global warming hiatus (GWH) was characterized by a La Niña-like cooling in the tropical Eastern Pacific accompanied with the Indian Ocean and the tropical Atlantic Ocean warming. Here we show that the recent GWH contributed significantly to the increased occurrence of intense tropical cyclones in the coastal regions along East Asia since 1998. The GWH associated sea surface temperature anomalies triggered a pair of anomalous cyclonic and anticyclonic circulations and equatorial easterly anomalies over the Northwest Pacific, which favored TC genesis and intensification over the western Northwest Pacific but suppressed TC genesis and intensification over the southeastern Northwest Pacific due to increased vertical wind shear and anticyclonic circulation anomalies. Results from atmospheric general circulation model experiments demonstrate that the Pacific La Niña-like cooling dominated the Indian Ocean and the tropical Atlantic Ocean warming in contributing to the observed GWH-related anomalous atmospheric circulation over the Northwest Pacific.