One of the basic characteristics of Earth's modern climate is that the Northern Hemisphere(NH) is climatologically warmer than the Southern Hemisphere(SH). Here, model performances of this basic state are examined...One of the basic characteristics of Earth's modern climate is that the Northern Hemisphere(NH) is climatologically warmer than the Southern Hemisphere(SH). Here, model performances of this basic state are examined using simulation results from 26 CMIP6 models. Results show that the CMIP6 models underestimate the contrast in interhemispheric surface temperatures on average(0.8 K for CMIP6 mean versus 1.4 K for reanalysis data mean), and that there is a large intermodel spread, ranging from -0.7 K to 2.3 K. A box model energy budget analysis shows that the contrast in interhemispheric shortwave absorption at the top of the atmosphere, the contrast in interhemispheric greenhouse trapping, and the crossequatorial northward ocean heat transport, are all underestimated in the multimodel mean. By examining the intermodel spread, we find intermodel biases can be tracked back to biases in midlatitude shortwave cloud forcing in AGCMs. Models with a weaker interhemispheric temperature contrast underestimate the shortwave cloud reflection in the SH but overestimate the shortwave cloud reflection in the NH, which are respectively due to underestimation of the cloud fraction over the SH extratropical ocean and overestimation of the cloud liquid water content over the NH extratropical continents.Models that underestimate the interhemispheric temperature contrast exhibit larger double ITCZ biases, characterized by excessive precipitation in the SH tropics. Although this intermodel spread does not account for the multimodel ensemble mean biases, it highlights that improving cloud simulation in AGCMs is essential for simulating the climate realistically in coupled models.展开更多
In this review,instead of summarizing all the advances and progress achieved in stratospheric research,the main advances and new developments in stratosphere-troposphere coupling and stratospheric chemistry-climate in...In this review,instead of summarizing all the advances and progress achieved in stratospheric research,the main advances and new developments in stratosphere-troposphere coupling and stratospheric chemistry-climate interactions are summarized,and some outstanding issues and grand challenges are discussed.A consensus has been reached that the stratospheric state is an important source of improving the predictability of the troposphere on sub-seasonal to seasonal(S2S)time scales and beyond.However,applying stratospheric signals in operational S2S forecast models remains a challenge because of model deficiencies and the complexities of the underlying mechanisms of stratosphere-troposphere coupling.Stratospheric chemistry,which controls the magnitude and distribution of many important climate-forcing agents,plays a critical role in global climate change.Convincing evidence has been found that stratospheric ozone depletion and recovery have caused significant tropospheric climate changes,and more recent studies have revealed that stratospheric ozone variations can even exert an impact on SSTs and sea ice.The climatic impacts of stratospheric aerosols and water vapor are also important.Although their quantitative contributions to radiative forcing have been reasonably well quantified,there still exist large uncertainties in their long-term impacts on climate.The advances and new levels of understanding presented in this review suggest that whole-atmosphere interactions need to be considered in future for a better and more thorough understanding of stratosphere-troposphere coupling and its role in climate change.展开更多
Perovskite solar cells(PSCs)show great potential for next-generation photovoltaics,due to their excellent optical and electrical properties.However,defects existing inside the perovskite film impair both the performan...Perovskite solar cells(PSCs)show great potential for next-generation photovoltaics,due to their excellent optical and electrical properties.However,defects existing inside the perovskite film impair both the performance and stability of the device.Uncoordinated Pb^(2+),uncoordinated I^(-),and metallic Pb(Pb^(0))are the main defects occur during perovskite film preparation and device operation,due to the volatilization of organic cationic components.Passivating these defects is a desirable tas k,because they are non-radiative recombination centers that cause open-circuit voltage(VOC)loss and degradation of the perovskite layer.Herein,the multifunctional bioactive compound dopamine(DA)is introduced for the first time to control the perovskite film formation and passivate the uncoordinated Pb^(2+)defects via Lewis acid-base interactions.The Pb^(0) and I^(-)defects are effectively suppressed by the DA treatment.At the same time,the DA treatment results in a stronger crystal orientation along the(110)plane and upshifts the valence band of perovskite closer to the highest occupied molecular orbital(HOMO)of the hole transport layer(2,2’,7,7’-tetrakis(N,N’-di-pmethoxyphenylamine)-9,9’-spirobifluorene,spiro-OMeTAD),which is beneficial for charge separation and transport processes.Consequently,the stability of MAPbI_(3)(MA=CH_(3)NH_(3))PSCs prepared with the DA additive(especially the thermal stability)is effectively improved due to the better crystallinity and lower number of defect trap states of the perovskite film.The optimized MAPbI3 PSCs maintain approximately 90% of their original power conversion efficiency(PCE)upon annealing at 85℃ for 120 h.The best performance triple-cation perovskite(Cs_(0.05)(FA_(0.83)MA_(0.17))_(0.95)Pb(I_(0.83)Br_(0.17))_(3))(FA=formamidinium)solar cell with ITO/SnO_(2)/Cs_(0.05)(FA_(0.83)MA_(0.17))_(0.95)Pb(I_(0.83)Br_(0.17))_(3):DA/spiro-OMeTAD/MoO_(3)/Ag(ITO=indium tin oxide)structure shows a PCE of 21.03% with negligible hysteresis,which is dramatically enhanced compared to that of the control device(18.31%).Therefore,this work presents a simple and effective way to improve the efficiency and stability of PSCs by DA treatment.展开更多
Total column ozone(TCO)over the Tibetan Plateau(TP)is lower than that over other regions at the same latitude,particularly in summer.This feature is known as the“TP ozone valley”.This study evaluates long-term chang...Total column ozone(TCO)over the Tibetan Plateau(TP)is lower than that over other regions at the same latitude,particularly in summer.This feature is known as the“TP ozone valley”.This study evaluates long-term changes in TCO and the ozone valley over the TP from 1984 to 2100 using Coupled Model Intercomparison Project Phase 6(CMIP6).The TP ozone valley consists of two low centers,one is located in the upper troposphere and lower stratosphere(UTLS),and the other is in the middle and upper stratosphere.Overall,the CMIP6 models simulate the low ozone center in the UTLS well and capture the spatial characteristics and seasonal cycle of the TP ozone valley,with spatial correlation coefficients between the modeled TCO and the Multi Sensor Reanalysis version 2(MSR2)TCO observations greater than 0.8 for all CMIP6 models.Further analysis reveals that models which use fully coupled and online stratospheric chemistry schemes simulate the anticorrelation between the 150 hPa geopotential height and zonal anomaly of TCO over the TP better than models without interactive chemistry schemes.This suggests that coupled chemical-radiative-dynamical processes play a key role in the simulation of the TP ozone valley.Most CMIP6 models underestimate the low center in the middle and upper stratosphere when compared with the Microwave Limb Sounder(MLS)observations.However,the bias in the middle and upper stratospheric ozone simulations has a marginal effect on the simulation of the TP ozone valley.Most CMIP6 models predict the TP ozone valley in summer will deepen in the future.展开更多
Record ozone loss was observed in the Arctic stratosphere in spring 2020.This study aims to determine what caused the extreme Arctic ozone loss.Observations and simulation results are examined in order to show that th...Record ozone loss was observed in the Arctic stratosphere in spring 2020.This study aims to determine what caused the extreme Arctic ozone loss.Observations and simulation results are examined in order to show that the extreme Arctic ozone loss was likely caused by record-high sea surface temperatures(SSTs)in the North Pacific.It is found that the record Arctic ozone loss was associated with the extremely cold and persistent stratospheric polar vortex over February-April,and the extremely cold vortex was a result of anomalously weak planetary wave activity.Further analysis reveals that the weak wave activity can be traced to anomalously warm SSTs in the North Pacific.Both observations and simulations show that warm SST anomalies in the North Pacific could have caused the weakening of wavenumber-1 wave activity,colder Arctic vortex,and lower Arctic ozone.These results suggest that for the present-day level of ozone-depleting substances,severe Arctic ozone loss could form again,as long as certain dynamic conditions are satisfied.展开更多
Fatigue crack growth tests were carried out on the SEN B3 precracked specimens, with dimensions in accordance with ISO 12108 requirements. The specimens were made of martensitic stainless steel, X17CrNi15-2, and some ...Fatigue crack growth tests were carried out on the SEN B3 precracked specimens, with dimensions in accordance with ISO 12108 requirements. The specimens were made of martensitic stainless steel, X17CrNi15-2, and some of them were modified by the ceramic coating deposition surface treatment. The effects of ceramic coating, on the fatigue crack growth behaviour of hollow shaft specimens, were experimentally investigated. Fatigue crack growth rates, da/dN, were characterised, using the power law relationship between da/dN (in mm/cycle) and the stress intensity factor range, ΔK (in MPa∙m0.5). The two constants of the correlation are 7.9768 × 10−9 and 2.8107 for the parent material, and those for the coated material are 2.4391 × 10−9 and 3.1990, respectively. Microstructural analyses were carried out on the tested specimens, which shows that the maximum hardness of the ceramic coating is higher than that of substrate by a factor of ~3.2. The dimple fracture dominates the final fracture mechanism for the parent material, and the combination of fatigue, ductile fracture and cleavage dominates the final fracture mechanism for the coated material, based on the SEM analyses. EDS tests’ results reveal that the parent material specimen shows higher levels of C at matrix regions along with Fe- and O-rich regions, compared with the coated material specimen.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 41888101)。
文摘One of the basic characteristics of Earth's modern climate is that the Northern Hemisphere(NH) is climatologically warmer than the Southern Hemisphere(SH). Here, model performances of this basic state are examined using simulation results from 26 CMIP6 models. Results show that the CMIP6 models underestimate the contrast in interhemispheric surface temperatures on average(0.8 K for CMIP6 mean versus 1.4 K for reanalysis data mean), and that there is a large intermodel spread, ranging from -0.7 K to 2.3 K. A box model energy budget analysis shows that the contrast in interhemispheric shortwave absorption at the top of the atmosphere, the contrast in interhemispheric greenhouse trapping, and the crossequatorial northward ocean heat transport, are all underestimated in the multimodel mean. By examining the intermodel spread, we find intermodel biases can be tracked back to biases in midlatitude shortwave cloud forcing in AGCMs. Models with a weaker interhemispheric temperature contrast underestimate the shortwave cloud reflection in the SH but overestimate the shortwave cloud reflection in the NH, which are respectively due to underestimation of the cloud fraction over the SH extratropical ocean and overestimation of the cloud liquid water content over the NH extratropical continents.Models that underestimate the interhemispheric temperature contrast exhibit larger double ITCZ biases, characterized by excessive precipitation in the SH tropics. Although this intermodel spread does not account for the multimodel ensemble mean biases, it highlights that improving cloud simulation in AGCMs is essential for simulating the climate realistically in coupled models.
基金supported by the National Natural Science Foundation of China(Grant Nos.42175089,42121004 and 42142038).
文摘In this review,instead of summarizing all the advances and progress achieved in stratospheric research,the main advances and new developments in stratosphere-troposphere coupling and stratospheric chemistry-climate interactions are summarized,and some outstanding issues and grand challenges are discussed.A consensus has been reached that the stratospheric state is an important source of improving the predictability of the troposphere on sub-seasonal to seasonal(S2S)time scales and beyond.However,applying stratospheric signals in operational S2S forecast models remains a challenge because of model deficiencies and the complexities of the underlying mechanisms of stratosphere-troposphere coupling.Stratospheric chemistry,which controls the magnitude and distribution of many important climate-forcing agents,plays a critical role in global climate change.Convincing evidence has been found that stratospheric ozone depletion and recovery have caused significant tropospheric climate changes,and more recent studies have revealed that stratospheric ozone variations can even exert an impact on SSTs and sea ice.The climatic impacts of stratospheric aerosols and water vapor are also important.Although their quantitative contributions to radiative forcing have been reasonably well quantified,there still exist large uncertainties in their long-term impacts on climate.The advances and new levels of understanding presented in this review suggest that whole-atmosphere interactions need to be considered in future for a better and more thorough understanding of stratosphere-troposphere coupling and its role in climate change.
基金financially supported by the National Natural Science Foundation of China(No.61974045)the Natural Science Foundation of Guangdong Province(Nos.2019A1515012092 and 2017A030313)+2 种基金the Key Laboratory of Functional Molecular Solids,Ministry of Education(No.FMS201905)the Guangdong Provincial Key Laboratory of New and Renewable Energy Research and Development(No.Y909kp1001)a project funded by the Science and Technology Bureau of the Dongguan Government(No.2019622163008)。
文摘Perovskite solar cells(PSCs)show great potential for next-generation photovoltaics,due to their excellent optical and electrical properties.However,defects existing inside the perovskite film impair both the performance and stability of the device.Uncoordinated Pb^(2+),uncoordinated I^(-),and metallic Pb(Pb^(0))are the main defects occur during perovskite film preparation and device operation,due to the volatilization of organic cationic components.Passivating these defects is a desirable tas k,because they are non-radiative recombination centers that cause open-circuit voltage(VOC)loss and degradation of the perovskite layer.Herein,the multifunctional bioactive compound dopamine(DA)is introduced for the first time to control the perovskite film formation and passivate the uncoordinated Pb^(2+)defects via Lewis acid-base interactions.The Pb^(0) and I^(-)defects are effectively suppressed by the DA treatment.At the same time,the DA treatment results in a stronger crystal orientation along the(110)plane and upshifts the valence band of perovskite closer to the highest occupied molecular orbital(HOMO)of the hole transport layer(2,2’,7,7’-tetrakis(N,N’-di-pmethoxyphenylamine)-9,9’-spirobifluorene,spiro-OMeTAD),which is beneficial for charge separation and transport processes.Consequently,the stability of MAPbI_(3)(MA=CH_(3)NH_(3))PSCs prepared with the DA additive(especially the thermal stability)is effectively improved due to the better crystallinity and lower number of defect trap states of the perovskite film.The optimized MAPbI3 PSCs maintain approximately 90% of their original power conversion efficiency(PCE)upon annealing at 85℃ for 120 h.The best performance triple-cation perovskite(Cs_(0.05)(FA_(0.83)MA_(0.17))_(0.95)Pb(I_(0.83)Br_(0.17))_(3))(FA=formamidinium)solar cell with ITO/SnO_(2)/Cs_(0.05)(FA_(0.83)MA_(0.17))_(0.95)Pb(I_(0.83)Br_(0.17))_(3):DA/spiro-OMeTAD/MoO_(3)/Ag(ITO=indium tin oxide)structure shows a PCE of 21.03% with negligible hysteresis,which is dramatically enhanced compared to that of the control device(18.31%).Therefore,this work presents a simple and effective way to improve the efficiency and stability of PSCs by DA treatment.
基金supported by the second Tibetan Plateau Scientific Expedition and Research Program (STEP,2019QZKK0604)the National Natural Science Foundation of China (Grant Nos.42075062 and 91837311)+1 种基金supported by the Fundamental Research Funds for the Central Universities (lzujbky-2021-ey04)NERC for financial support through NCAS
文摘Total column ozone(TCO)over the Tibetan Plateau(TP)is lower than that over other regions at the same latitude,particularly in summer.This feature is known as the“TP ozone valley”.This study evaluates long-term changes in TCO and the ozone valley over the TP from 1984 to 2100 using Coupled Model Intercomparison Project Phase 6(CMIP6).The TP ozone valley consists of two low centers,one is located in the upper troposphere and lower stratosphere(UTLS),and the other is in the middle and upper stratosphere.Overall,the CMIP6 models simulate the low ozone center in the UTLS well and capture the spatial characteristics and seasonal cycle of the TP ozone valley,with spatial correlation coefficients between the modeled TCO and the Multi Sensor Reanalysis version 2(MSR2)TCO observations greater than 0.8 for all CMIP6 models.Further analysis reveals that models which use fully coupled and online stratospheric chemistry schemes simulate the anticorrelation between the 150 hPa geopotential height and zonal anomaly of TCO over the TP better than models without interactive chemistry schemes.This suggests that coupled chemical-radiative-dynamical processes play a key role in the simulation of the TP ozone valley.Most CMIP6 models underestimate the low center in the middle and upper stratosphere when compared with the Microwave Limb Sounder(MLS)observations.However,the bias in the middle and upper stratospheric ozone simulations has a marginal effect on the simulation of the TP ozone valley.Most CMIP6 models predict the TP ozone valley in summer will deepen in the future.
基金We thank Dr.Jian YUE for helpful com-ments.This work is supported by the National Natural Science Foundation of China(NSFC)under Grant No.41888101.Y.XIA is supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP),Grant No.2019QZKK0604,Key Laboratory of Middle Atmosphere and Global Environment Observa-tion(LAGEO-2020-09)the Fundamental Research Funds for the Central Universities.
文摘Record ozone loss was observed in the Arctic stratosphere in spring 2020.This study aims to determine what caused the extreme Arctic ozone loss.Observations and simulation results are examined in order to show that the extreme Arctic ozone loss was likely caused by record-high sea surface temperatures(SSTs)in the North Pacific.It is found that the record Arctic ozone loss was associated with the extremely cold and persistent stratospheric polar vortex over February-April,and the extremely cold vortex was a result of anomalously weak planetary wave activity.Further analysis reveals that the weak wave activity can be traced to anomalously warm SSTs in the North Pacific.Both observations and simulations show that warm SST anomalies in the North Pacific could have caused the weakening of wavenumber-1 wave activity,colder Arctic vortex,and lower Arctic ozone.These results suggest that for the present-day level of ozone-depleting substances,severe Arctic ozone loss could form again,as long as certain dynamic conditions are satisfied.
文摘Fatigue crack growth tests were carried out on the SEN B3 precracked specimens, with dimensions in accordance with ISO 12108 requirements. The specimens were made of martensitic stainless steel, X17CrNi15-2, and some of them were modified by the ceramic coating deposition surface treatment. The effects of ceramic coating, on the fatigue crack growth behaviour of hollow shaft specimens, were experimentally investigated. Fatigue crack growth rates, da/dN, were characterised, using the power law relationship between da/dN (in mm/cycle) and the stress intensity factor range, ΔK (in MPa∙m0.5). The two constants of the correlation are 7.9768 × 10−9 and 2.8107 for the parent material, and those for the coated material are 2.4391 × 10−9 and 3.1990, respectively. Microstructural analyses were carried out on the tested specimens, which shows that the maximum hardness of the ceramic coating is higher than that of substrate by a factor of ~3.2. The dimple fracture dominates the final fracture mechanism for the parent material, and the combination of fatigue, ductile fracture and cleavage dominates the final fracture mechanism for the coated material, based on the SEM analyses. EDS tests’ results reveal that the parent material specimen shows higher levels of C at matrix regions along with Fe- and O-rich regions, compared with the coated material specimen.
基金supported by Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(SML2021SP312)the National Natural Science Foundation of China(4207506242130601,and 41922044)+3 种基金the National Key Research&Development Program of China(2018YFC1506003)the Fundamental Research Funds for the Central Universities,China(lzujbky-2021ey04)Young Doctoral Funds for Gansu Provincial Education Department(2021QB-009)supported by Supercomputing Center of Lanzhou University。