Considering the atmospheric extinction and turbulence effects,we investigate the propagation performances of supercontinuum laser sources in atmospheric turbulence statistically by using the numerical simulation metho...Considering the atmospheric extinction and turbulence effects,we investigate the propagation performances of supercontinuum laser sources in atmospheric turbulence statistically by using the numerical simulation method,and the differences in propagation properties between the super-continuum(SC)laser and its pump laser are also analyzed.It is found that the propagation characteristics of super-continuum laser are almost similar to those of the pump laser.The degradation of source coherence degree may cause the relative beam spreading and scintillation indexes to decrease at different propagation distances or different turbulence strengths.The root-mean-square value of beam wandering is insensitive to the variation of source correlation length,and less aperture averaging occurs when the laser source becomes less coherent.Additionally,from the point of view of beam wandering,the SC laser has no advantage over the pump laser.Although the pump laser can bring about a bigger aperture average,the SC laser has a lower scintillation which may be due to the multiple wavelength homogenization effects on intensity fluctuations.This would be the most important virtue of the SC laser that can be utilized to improve the performance of laser engineering.展开更多
This report reviews the researches for the middle and upper atmosphere in 2020-2022 by Chinese scientists.The report consists of five parts introducing primarily the results from the aspects of the development of infr...This report reviews the researches for the middle and upper atmosphere in 2020-2022 by Chinese scientists.The report consists of five parts introducing primarily the results from the aspects of the development of infrastructure,the structure and composition,the climate and modeling,the dynamics for the middle and upper atmosphere,and Coupling between Stratosphere and Troposphere,respectively.展开更多
Restoration of phase aberrations is crucial for addressing atmospheric turbulence in light propagation.Traditional restoration algorithms based on Zernike polynomials(ZPs)often encounter challenges related to high com...Restoration of phase aberrations is crucial for addressing atmospheric turbulence in light propagation.Traditional restoration algorithms based on Zernike polynomials(ZPs)often encounter challenges related to high computational complexity and insufficient capture of high-frequency phase aberration components,so we proposed a Principal-Component-Analysis-based method for representing phase aberrations.This paper discusses the factors influencing the accuracy of restoration,mainly including the sample space size and the sampling interval of D/r_(0),on the basis of characterizing phase aberrations by Principal Components(PCs).The experimental results show that a larger D/r_(0)sampling interval can ensure the generalization ability and robustness of the principal components in the case of a limited amount of original data,which can help to achieve high-precision deployment of the model in practical applications quickly.In the environment with relatively strong turbulence in the test set of D/r_(0)=24,the use of 34 terms of PCs can improve the corrected Strehl ratio(SR)from 0.007 to 0.1585,while the Strehl ratio of the light spot after restoration using 34 terms of ZPs is only 0.0215,demonstrating almost no correction effect.The results indicate that PCs can serve as a better alternative in representing and restoring the characteristics of atmospheric turbulence induced phase aberrations.These findings pave the way to use PCs of phase aberrations with fewer terms than traditional ZPs to achieve data dimensionality reduction,and offer a reference to accelerate and stabilize the model and deep learning based adaptive optics correction.展开更多
The southern part of East Siberia(SES)is highly vulnerable to flooding caused by the extreme precipitation events(EPEs)during summer.Building on previously detected EPEs in SES and Mongolia,we examined wave propagatio...The southern part of East Siberia(SES)is highly vulnerable to flooding caused by the extreme precipitation events(EPEs)during summer.Building on previously detected EPEs in SES and Mongolia,we examined wave propagation patterns for two periods:1982-98 and 1999-2019.Our analysis revealed distinct wave train configurations and geopotential anomalies preceding EPEs,with an increase in wave activity flux across the Northern Hemisphere,followed by a subsequent decrease during EPEs.Consequently,Eastern Siberia has experienced a significant rise in wave activity.Based on geopotential anomalies over Central Siberia accompanying EPEs,we identified two main types.The first,the ridge type,is predominant during the first period and features a meridional contrast with a positive geopotential(and temperature)anomaly over Central Siberia and a negative anomaly over the subtropical regions along the same longitude.The second type,termed the trough type,is more typical for the second period.It involves either a negative geopotential anomaly or the zonal proximity of positive and negative geopotential anomalies over Central Siberia.The trough type,marked by zonally oriented anomalies in geopotential and temperature,results in a more pronounced temperature decrease before EPEs and significant zonal temperature contrasts.Further,it is related to more stationary waves over Northern Eurasia,with persistent positive geopotential anomalies over Europe linked to quasi-stationary troughs over Central Siberia and positive anomalies east of Lake Baikal.Our findings align with shifts in boreal summer teleconnection patterns,reflecting significant changes in wave propagation patterns that have occurred since the late 1990s.展开更多
Atmospheric turbulence is an important parameter affecting laser atmospheric transmission.This paper reports on a self-developed atmospheric turbulence detection Li DAR system(scanning differential image motion Li DAR...Atmospheric turbulence is an important parameter affecting laser atmospheric transmission.This paper reports on a self-developed atmospheric turbulence detection Li DAR system(scanning differential image motion Li DAR(DIM-Li DAR)system).By designing and simulating the optical system of atmospheric turbulence detection Li DAR,the basic optical imaging accuracy has been determined.展开更多
The melting process of ice crystal particles has a significant effect on weather forecasting and global climate.Millimeter waveband is an excellent frequency range for exploring the optical characteristics of ice crys...The melting process of ice crystal particles has a significant effect on weather forecasting and global climate.Millimeter waveband is an excellent frequency range for exploring the optical characteristics of ice crystal particles.In this study,a new nonspherical and inhomogeneous ice crystal particle model is built based on the melting process of ice crystal particles.The single-scattering characteristics of ice crystal particles with different frequencies,sizes,shapes and ice crystal content(ICC)are investigated using the discrete dipole approximation(DDA)method.The results show that the single-scattering characteristics of ice crystal particles are closely related to the equivalent radius,frequency,morphology and mixing state.The single-scattering properties of the particles change regularly with the melting process of the ice crystal particles.Specifically,in the early stage of the ice crystal particle melting process,the single-scattering characteristics of ice crystal particles change significantly.With further melting,the change in the single-scattering characteristics of ice crystal particles gradually slows down when the ICC is less than 0.5.The results also show that in the early stage of the melting process,the shape of the ice crystal particles has a huge influence on the single-scattering characteristics of the particles,and in the late stage of the melting process,the single-scattering characteristics of the ice crystal particles are basically independent of the morphology of the ice crystal nuclei.This means that the influence of the morphology of the ice crystal nuclei needs to be considered in phases when simulating the scattering characteristics of the melting ice crystal particles.In summary,the results of this study should improve our understanding of the effect of size parameter,morphology and mixing state on the millimeter-wave scattering characteristics of ice clouds during the melting process and provide a reference for the remote sensing inversion of ice cloud microphysical characteristics.展开更多
LithiumvanadatesLiV_(3)O_(8)-LiV_(6)O_(15)(LVO)witha heterojunction structure are synthesized using a conventional high-temperature solid-state method to address the challenges of low ionic conductivity,rapid capacity...LithiumvanadatesLiV_(3)O_(8)-LiV_(6)O_(15)(LVO)witha heterojunction structure are synthesized using a conventional high-temperature solid-state method to address the challenges of low ionic conductivity,rapid capacity decay,and poor cycling performance in conventional lithium-ion battery cathode materials.The charge-discharge processes of LVO span multiple platforms,delivering an impressive specific discharge capacity of 219.4 mAh.g^(-1) at 1C.Remarkably,LVO exhibits a high-capacity retention rate of 81.3%after 800 cycles within the typical operating voltage range of lithium-ion batteries(2.8-4.3V).Rate capability tests and electrochemical impedance spectroscopy(EIS)reveal that,compared to traditional cathode materials,LVO significantly enhances Li*diffusion rates(D_(Li*))and reduces charge transfer resistance(Ret).展开更多
Visibility is an important atmospheric parameter that is gaining increasing global attention. This study introduces a back-propagation neural network method based on genetic algorithm optimization to obtain visibility...Visibility is an important atmospheric parameter that is gaining increasing global attention. This study introduces a back-propagation neural network method based on genetic algorithm optimization to obtain visibility directly using light detection and ranging(lidar) signals instead of acquiring extinction coefficient. We have validated the performance of the novel method by comparing it with the traditional inversion method, the back-propagation(BP) neural network method,and the Belfort, which is used as a standard value. The mean square error(MSE) and mean absolute percentage error(MAPE) values of the genetic algorithm-optimized back propagation(GABP) method are located in the range of 0.002 km2–0.005 km^2 and 1%–3%, respectively. However, the MSE and MAPE values of the traditional inversion method and the BP method are significantly higher than those of the GABP method. Our results indicate that the proposed algorithm achieves better performance and can be used as a valuable new approach for visibility estimation.展开更多
The unique geographical location and high altitude of the Tibetan Plateau can greatly influence regional weather and climate.In particular, the Asian summer monsoon(ASM) anticyclone circulation system over the Tibetan...The unique geographical location and high altitude of the Tibetan Plateau can greatly influence regional weather and climate.In particular, the Asian summer monsoon(ASM) anticyclone circulation system over the Tibetan Plateau is recognized to be a significant transport pathway for water vapor and pollutants to enter the stratosphere. To improve understanding of these physical processes, a multi-location joint atmospheric experiment was performed over the Tibetan Plateau from late July to August in 2018, funded by the fiveyear(2018–2022) STEAM(stratosphere and troposphere exchange experiment during ASM) project, during which multiple platforms/instruments—including long-duration stratospheric balloons, dropsondes, unmanned aerial vehicles, special sounding systems, and ground-based and satellite-borne instruments—will be deployed. These complementary methods of data acquisition are expected to provide comprehensive atmospheric parameters(aerosol, ozone, water vapor, CO_2, CH_4, CO, temperature, pressure,turbulence, radiation, lightning and wind); the richness of this approach is expected to advance our comprehension of key mechanisms associated with thermal, dynamical, radiative, and chemical transports over the Tibetan Plateau during ASM activity.展开更多
A numerical simulation model of plenoptic sensor aberration wavefront detection is established to simulate and analyze the detection performance of plenoptic sensor aberration wavefront for different turbulence intens...A numerical simulation model of plenoptic sensor aberration wavefront detection is established to simulate and analyze the detection performance of plenoptic sensor aberration wavefront for different turbulence intensities.The results show that the plenoptic sensor can achieve better distortion wavefront detection,and its wavefront detection accuracy improves with turbulence intensity.The unique optical structure design of the plenoptic sensor makes it more suitable for aberration wavefront detection in strong turbulent conditions.The wavefront detection performance of the plenoptic sensor is not only related to its wavefront reconstruction algorithm but also closely related to its structural parameter settings.The influence of structural parameters on the wavefront detection accuracy of plenoptic sensors under different turbulence intensities is simulated and analyzed.The variation law of wavefront detection accuracy and structural parameters under different turbulence intensities is summarized to provide a reference for the structural design and parameter optimization of plenoptic sensors.展开更多
Accurate and comprehensive knowledge of the atmospheric environment and its evolution within the coastal ocean boundary layer are necessary for understanding the sources,chemical mechanisms,and transport processes of ...Accurate and comprehensive knowledge of the atmospheric environment and its evolution within the coastal ocean boundary layer are necessary for understanding the sources,chemical mechanisms,and transport processes of air pollution in land,sea,and atmosphere.We present an overview of coastal ocean boundary layer detection technology and equipment in China and summarize the progress and main achievements in recent years.China has developed a series of coastal ocean boundary layer detection technologies,including Light Detection and Ranging(LIDAR),turbulent exchange analyzer,air-sea flux analyzer,stereoscopic remote sensing of air pollutants,and oceanic aerosol detection equipment to address the technical bottleneck caused by harsh environmental conditions in coastal ocean regions.Advances in these technologies and equipment have provided scientific assistance for addressing air pollution issues and understanding land-sea-atmosphere interactions over coastal ocean regions in China.In the future,routine atmospheric observations should cover the coastal ocean boundary layer of China.展开更多
We find a new complex integration-transform which can establish a new relationship between a two-mode operator's matrix element in the entangled state representation and its Wigner function. This integration keeps...We find a new complex integration-transform which can establish a new relationship between a two-mode operator's matrix element in the entangled state representation and its Wigner function. This integration keeps modulus invariant and therefore invertible. Based on this and the Weyl–Wigner correspondence theory, we find a two-mode operator which is responsible for complex fractional squeezing transformation. The entangled state representation and the Weyl ordering form of the two-mode Wigner operator are fully used in our derivation which brings convenience.展开更多
Lake Baikal is the biggest reservoir of fresh water with unique flora and fauna;presently it is negatively affected by climate change, water warming, industrial emissions, shipping,touristic activities, and Siberian f...Lake Baikal is the biggest reservoir of fresh water with unique flora and fauna;presently it is negatively affected by climate change, water warming, industrial emissions, shipping,touristic activities, and Siberian forest fires.The assessment of air pollution-related Baikal’s ecosystem damage is an unsolved problem.Ship, based expedition exploring the Baikal atmospheric aerosol loading, was performed over the lake area in July 2018.We combine the aerosol near-water and vertical distributions over the Lake Baikal basin with meteorological observations and air mass transportation simulations.Lidar sounding of aerosol fields in the troposphere assesses the atmospheric background in the pristine areas and the pollution during fire-affected periods.Aerosol optical properties(scattering and spectral absorption) converted to the particle number size, black carbon(BC) mass, and Absorption Angstrom Exponent(AAE) provide the inside into aerosol characterization.Transport of industrial emissions from Krasnoyarsk and Irkutsk regions, and wildfire plumes from Republic of Yakutia relates the pollution sources to the increased concentrations of fine particle numbers, PM_(10) and BC mass over Southern and Northern/Central Baikal, respectively.The highest PM10 and BC are associated to the harbor and touristic areas of intensive shipping and residential biomass burning.Deposition estimates applied to aerosol data exhibit the pollution fluxes to water surface over the whole Baikal area.AAE marks the impact of coal combustion, residential biomass burning, and wildfires indicating the high pollution level of the Lake Baikal ecological system.展开更多
A new kind of lidar signal light-splitting system is presented to sum up different rotational Raman lines and to improve the signal to noise ratio(SNR) .The temperature parameters with high SNR of this new system have...A new kind of lidar signal light-splitting system is presented to sum up different rotational Raman lines and to improve the signal to noise ratio(SNR) .The temperature parameters with high SNR of this new system have been obtained with a normal laser and a small telescope from several kilometers.展开更多
Based on the TRMM dataset, this paper compares the applicability of the improved MCE(minimum circumscribed ellipse), MBR(minimum bounding rectangle), and DIA(direct indexing area) methods for rain cell fitting. These ...Based on the TRMM dataset, this paper compares the applicability of the improved MCE(minimum circumscribed ellipse), MBR(minimum bounding rectangle), and DIA(direct indexing area) methods for rain cell fitting. These three methods can reflect the geometric characteristics of clouds and apply geometric parameters to estimate the real dimensions of rain cells. The MCE method shows a major advantage in identifying the circumference of rain cells. The circumference of rain cells identified by MCE in most samples is smaller than that identified by DIA and MBR, and more similar to the observed rain cells. The area of rain cells identified by MBR is relatively robust. For rain cells composed of many pixels(N> 20), the overall performance is better than that of MCE, but the contribution of MBR to the best identification results,which have the shortest circumference and the smallest area, is less than that of MCE. The DIA method is best suited to small rain cells with a circumference of less than 100 km and an area of less than 120 km^(2), but the overall performance is mediocre. The MCE method tends to achieve the highest success at any angle, whereas there are fewer “best identification”results from DIA or MBR and more of the worst ones in the along-track direction and cross-track direction. Through this comprehensive comparison, we conclude that MCE can obtain the best fitting results with the shortest circumference and the smallest area on behalf of the high filling effect for all sizes of rain cells.展开更多
Cylindrical density depressions generated by femtosecond laser pulses filamenting in air for different energy depositions are investigated numerically, by using a set of hydrodynamic equations. The evolution of densit...Cylindrical density depressions generated by femtosecond laser pulses filamenting in air for different energy depositions are investigated numerically, by using a set of hydrodynamic equations. The evolution of density profile is calculated for different temperature elevations. The results indicate that the gas density hole is getting shallower and wider with the increasing temperature elevations. A simulation of the propagation inside low-density channel implies a new way to generate a type of bottle beam.展开更多
The paper introduces a new laser interferometry-based method for diagnosis of random media by means of high accuracy angle measurements and describes the results of its development and testing. Theoretical calculation...The paper introduces a new laser interferometry-based method for diagnosis of random media by means of high accuracy angle measurements and describes the results of its development and testing. Theoretical calculations of the dependence of the range of the laser interferometer on laser beam parameters, device geometry, and atmospheric turbulence characteristics are reported. It is demonstrated that at moderate turbulence intensities corresponding to those observed most frequently in turbulent atmosphere at moderate latitudes and with low interference contrast values, the performance range of the laser interferometer-based device exceeds 5 km.展开更多
Lake Baikal is one of the most unique natural environments in Siberia, and it affects to a large extent the natural state in this region. Processes of gas exchange in the air-water system have been studied in Lake Bai...Lake Baikal is one of the most unique natural environments in Siberia, and it affects to a large extent the natural state in this region. Processes of gas exchange in the air-water system have been studied in Lake Baikal since 2002. Measurements have been carried out in the littoral area on the western shore of Southern Baikal (51°51'N, 105°04'E). The method of accumulative chambers was prioritized for measuring carbon dioxide fluxes in the air-water system. Chemical analysis of the water samples collected every three hours at the chamber locations was carried out in the on-land laboratory. We measured pH, content of dissolved oxygen, bicarbonate, nitrate and phosphate. The CO2 content in the water was measured from pH values and the bicarbonate concentration. The total sink of CO2 on the water surface is increasing in the littoral area of Lake Baikal from 20 mg·CO2·m-2·day-1 in June to 110 mg·CO2·m-2·day-1 in August. The decrease in the flux rate usually begins in September from 95 mg·CO2·m-2·day-1 to the zero balance in late October - early November. The maximal rate of mean diurnal CO2 emissions is recorded in December in the pre-ice period (110 mg·CO2·m-2·day-1). Based on the long-term measurements during all seasons, the sink of atmospheric CO2 in the littoral zones of Lake Baikal was estimated to be 3 - 5 g·CO2·m-2.展开更多
Narrow bipolar events(NBEs)are intriguing intra-cloud discharge that have attracted enormous interest in the lightning community.They come with two polarities that dominate at different altitudes in thunderclouds.The ...Narrow bipolar events(NBEs)are intriguing intra-cloud discharge that have attracted enormous interest in the lightning community.They come with two polarities that dominate at different altitudes in thunderclouds.The sources of negative NBEs are usually located near the top of thunderclouds;those of positive NBEs are at the middle levels.NBEs may occur at the onset of lightning.The electrical properties of NBEs remain poorly understood.We present here the first comparative study of the electrical characteristics of negative and positive NBEs.To derive electrical parameters from the fast electric field change waveforms of 1673 positive NBEs and 364 negative NBEs recorded by the Jianghuai Area Sferic Array(JASA)in China,we use an improved method based on the transmission line model.This approach concludes that negative NBEs occurring at high altitudes tend to produce a narrower current pulse and take a shorter time to traverse the channel than their positive counterparts.Moreover,compared to positive NBEs,a larger portion of negative NBEs are associated with slightly greater peak current moments but smaller overall charge moments.The differences reported herein between electrical properties of negative and positive NBEs suggest that charge distribution in NBE-producing thunderstorms tends to vary systematically with altitude.展开更多
基金Project supported by the Director Fund of Advanced Laser Technology Laboratory of Anhui Province,China(Grant No.20191002).
文摘Considering the atmospheric extinction and turbulence effects,we investigate the propagation performances of supercontinuum laser sources in atmospheric turbulence statistically by using the numerical simulation method,and the differences in propagation properties between the super-continuum(SC)laser and its pump laser are also analyzed.It is found that the propagation characteristics of super-continuum laser are almost similar to those of the pump laser.The degradation of source coherence degree may cause the relative beam spreading and scintillation indexes to decrease at different propagation distances or different turbulence strengths.The root-mean-square value of beam wandering is insensitive to the variation of source correlation length,and less aperture averaging occurs when the laser source becomes less coherent.Additionally,from the point of view of beam wandering,the SC laser has no advantage over the pump laser.Although the pump laser can bring about a bigger aperture average,the SC laser has a lower scintillation which may be due to the multiple wavelength homogenization effects on intensity fluctuations.This would be the most important virtue of the SC laser that can be utilized to improve the performance of laser engineering.
文摘This report reviews the researches for the middle and upper atmosphere in 2020-2022 by Chinese scientists.The report consists of five parts introducing primarily the results from the aspects of the development of infrastructure,the structure and composition,the climate and modeling,the dynamics for the middle and upper atmosphere,and Coupling between Stratosphere and Troposphere,respectively.
文摘Restoration of phase aberrations is crucial for addressing atmospheric turbulence in light propagation.Traditional restoration algorithms based on Zernike polynomials(ZPs)often encounter challenges related to high computational complexity and insufficient capture of high-frequency phase aberration components,so we proposed a Principal-Component-Analysis-based method for representing phase aberrations.This paper discusses the factors influencing the accuracy of restoration,mainly including the sample space size and the sampling interval of D/r_(0),on the basis of characterizing phase aberrations by Principal Components(PCs).The experimental results show that a larger D/r_(0)sampling interval can ensure the generalization ability and robustness of the principal components in the case of a limited amount of original data,which can help to achieve high-precision deployment of the model in practical applications quickly.In the environment with relatively strong turbulence in the test set of D/r_(0)=24,the use of 34 terms of PCs can improve the corrected Strehl ratio(SR)from 0.007 to 0.1585,while the Strehl ratio of the light spot after restoration using 34 terms of ZPs is only 0.0215,demonstrating almost no correction effect.The results indicate that PCs can serve as a better alternative in representing and restoring the characteristics of atmospheric turbulence induced phase aberrations.These findings pave the way to use PCs of phase aberrations with fewer terms than traditional ZPs to achieve data dimensionality reduction,and offer a reference to accelerate and stabilize the model and deep learning based adaptive optics correction.
文摘The southern part of East Siberia(SES)is highly vulnerable to flooding caused by the extreme precipitation events(EPEs)during summer.Building on previously detected EPEs in SES and Mongolia,we examined wave propagation patterns for two periods:1982-98 and 1999-2019.Our analysis revealed distinct wave train configurations and geopotential anomalies preceding EPEs,with an increase in wave activity flux across the Northern Hemisphere,followed by a subsequent decrease during EPEs.Consequently,Eastern Siberia has experienced a significant rise in wave activity.Based on geopotential anomalies over Central Siberia accompanying EPEs,we identified two main types.The first,the ridge type,is predominant during the first period and features a meridional contrast with a positive geopotential(and temperature)anomaly over Central Siberia and a negative anomaly over the subtropical regions along the same longitude.The second type,termed the trough type,is more typical for the second period.It involves either a negative geopotential anomaly or the zonal proximity of positive and negative geopotential anomalies over Central Siberia.The trough type,marked by zonally oriented anomalies in geopotential and temperature,results in a more pronounced temperature decrease before EPEs and significant zonal temperature contrasts.Further,it is related to more stationary waves over Northern Eurasia,with persistent positive geopotential anomalies over Europe linked to quasi-stationary troughs over Central Siberia and positive anomalies east of Lake Baikal.Our findings align with shifts in boreal summer teleconnection patterns,reflecting significant changes in wave propagation patterns that have occurred since the late 1990s.
基金jointly funded by the National Science Foundation of China(No.42405069)the University Natural Sciences Research Project of Anhui Province(Nos.2023AH052201 and 2023AH052184)+1 种基金the 2023 Talent Research Fund Project of Hefei University(No.23RC01)the Technical Development Project of Hefei University(Nos.902/22050124128,902/22050124148 and 902/22050124250)。
文摘Atmospheric turbulence is an important parameter affecting laser atmospheric transmission.This paper reports on a self-developed atmospheric turbulence detection Li DAR system(scanning differential image motion Li DAR(DIM-Li DAR)system).By designing and simulating the optical system of atmospheric turbulence detection Li DAR,the basic optical imaging accuracy has been determined.
基金supported by the National Key Research and Development Program of China(Grant No.2019YFA0706004)the Key Projects of Science and Technology Research of Henan Province(Grant No.222102320087)the Key Scientific Research Project of Colleges and Universities in Henan Province(Grant No.25B170004).
文摘The melting process of ice crystal particles has a significant effect on weather forecasting and global climate.Millimeter waveband is an excellent frequency range for exploring the optical characteristics of ice crystal particles.In this study,a new nonspherical and inhomogeneous ice crystal particle model is built based on the melting process of ice crystal particles.The single-scattering characteristics of ice crystal particles with different frequencies,sizes,shapes and ice crystal content(ICC)are investigated using the discrete dipole approximation(DDA)method.The results show that the single-scattering characteristics of ice crystal particles are closely related to the equivalent radius,frequency,morphology and mixing state.The single-scattering properties of the particles change regularly with the melting process of the ice crystal particles.Specifically,in the early stage of the ice crystal particle melting process,the single-scattering characteristics of ice crystal particles change significantly.With further melting,the change in the single-scattering characteristics of ice crystal particles gradually slows down when the ICC is less than 0.5.The results also show that in the early stage of the melting process,the shape of the ice crystal particles has a huge influence on the single-scattering characteristics of the particles,and in the late stage of the melting process,the single-scattering characteristics of the ice crystal particles are basically independent of the morphology of the ice crystal nuclei.This means that the influence of the morphology of the ice crystal nuclei needs to be considered in phases when simulating the scattering characteristics of the melting ice crystal particles.In summary,the results of this study should improve our understanding of the effect of size parameter,morphology and mixing state on the millimeter-wave scattering characteristics of ice clouds during the melting process and provide a reference for the remote sensing inversion of ice cloud microphysical characteristics.
基金supported by the National Natural Science Foundation of China(Nos.52125405 and U22A20108)Thailand Science Research and Innovation Fund Chulalongkorn University,National Research Council of Thailand(NRCT)+1 种基金Chulalongkorn University(No.42A660383)the Hub of Talents:Sustainable Materials for Circular Economy,National Research Council of Thailand(NRCT).
文摘LithiumvanadatesLiV_(3)O_(8)-LiV_(6)O_(15)(LVO)witha heterojunction structure are synthesized using a conventional high-temperature solid-state method to address the challenges of low ionic conductivity,rapid capacity decay,and poor cycling performance in conventional lithium-ion battery cathode materials.The charge-discharge processes of LVO span multiple platforms,delivering an impressive specific discharge capacity of 219.4 mAh.g^(-1) at 1C.Remarkably,LVO exhibits a high-capacity retention rate of 81.3%after 800 cycles within the typical operating voltage range of lithium-ion batteries(2.8-4.3V).Rate capability tests and electrochemical impedance spectroscopy(EIS)reveal that,compared to traditional cathode materials,LVO significantly enhances Li*diffusion rates(D_(Li*))and reduces charge transfer resistance(Ret).
基金Project supported by the National Natural Science Foundation of China(Grant No.41405014)
文摘Visibility is an important atmospheric parameter that is gaining increasing global attention. This study introduces a back-propagation neural network method based on genetic algorithm optimization to obtain visibility directly using light detection and ranging(lidar) signals instead of acquiring extinction coefficient. We have validated the performance of the novel method by comparing it with the traditional inversion method, the back-propagation(BP) neural network method,and the Belfort, which is used as a standard value. The mean square error(MSE) and mean absolute percentage error(MAPE) values of the genetic algorithm-optimized back propagation(GABP) method are located in the range of 0.002 km2–0.005 km^2 and 1%–3%, respectively. However, the MSE and MAPE values of the traditional inversion method and the BP method are significantly higher than those of the GABP method. Our results indicate that the proposed algorithm achieves better performance and can be used as a valuable new approach for visibility estimation.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant Nos. XDA17010101, XDA17010102, XDA17010103, XDA17010104 and XDA17010105)
文摘The unique geographical location and high altitude of the Tibetan Plateau can greatly influence regional weather and climate.In particular, the Asian summer monsoon(ASM) anticyclone circulation system over the Tibetan Plateau is recognized to be a significant transport pathway for water vapor and pollutants to enter the stratosphere. To improve understanding of these physical processes, a multi-location joint atmospheric experiment was performed over the Tibetan Plateau from late July to August in 2018, funded by the fiveyear(2018–2022) STEAM(stratosphere and troposphere exchange experiment during ASM) project, during which multiple platforms/instruments—including long-duration stratospheric balloons, dropsondes, unmanned aerial vehicles, special sounding systems, and ground-based and satellite-borne instruments—will be deployed. These complementary methods of data acquisition are expected to provide comprehensive atmospheric parameters(aerosol, ozone, water vapor, CO_2, CH_4, CO, temperature, pressure,turbulence, radiation, lightning and wind); the richness of this approach is expected to advance our comprehension of key mechanisms associated with thermal, dynamical, radiative, and chemical transports over the Tibetan Plateau during ASM activity.
基金the National Natural Science Foundation of China(No.61605223)the Strategic Priority Research Program of Chinese Academy of Sciences(No.614A010717)the Director Fund of Advanced Laser Technology Laboratory of Anhui Province(No.AHL2021ZR06)。
文摘A numerical simulation model of plenoptic sensor aberration wavefront detection is established to simulate and analyze the detection performance of plenoptic sensor aberration wavefront for different turbulence intensities.The results show that the plenoptic sensor can achieve better distortion wavefront detection,and its wavefront detection accuracy improves with turbulence intensity.The unique optical structure design of the plenoptic sensor makes it more suitable for aberration wavefront detection in strong turbulent conditions.The wavefront detection performance of the plenoptic sensor is not only related to its wavefront reconstruction algorithm but also closely related to its structural parameter settings.The influence of structural parameters on the wavefront detection accuracy of plenoptic sensors under different turbulence intensities is simulated and analyzed.The variation law of wavefront detection accuracy and structural parameters under different turbulence intensities is summarized to provide a reference for the structural design and parameter optimization of plenoptic sensors.
基金supported by the National Key Research and Development Program of China(Nos.2018YFC0213106,2018YFC0213101,2018YFC0213102,2018YFC0213103,2018YFC0213104 and 2018YFC0213105)Anhui Provincial Natural Science Foundation(No.2108085QD177)the CASHIPS Director’s Fund(No.YZJJ2021QN07)。
文摘Accurate and comprehensive knowledge of the atmospheric environment and its evolution within the coastal ocean boundary layer are necessary for understanding the sources,chemical mechanisms,and transport processes of air pollution in land,sea,and atmosphere.We present an overview of coastal ocean boundary layer detection technology and equipment in China and summarize the progress and main achievements in recent years.China has developed a series of coastal ocean boundary layer detection technologies,including Light Detection and Ranging(LIDAR),turbulent exchange analyzer,air-sea flux analyzer,stereoscopic remote sensing of air pollutants,and oceanic aerosol detection equipment to address the technical bottleneck caused by harsh environmental conditions in coastal ocean regions.Advances in these technologies and equipment have provided scientific assistance for addressing air pollution issues and understanding land-sea-atmosphere interactions over coastal ocean regions in China.In the future,routine atmospheric observations should cover the coastal ocean boundary layer of China.
基金Project supported by the National Natural Science Foundation of China(Grant No.11775208)Key Projects of Huainan Normal University,China(Grant No.2019XJZD04)。
文摘We find a new complex integration-transform which can establish a new relationship between a two-mode operator's matrix element in the entangled state representation and its Wigner function. This integration keeps modulus invariant and therefore invertible. Based on this and the Weyl–Wigner correspondence theory, we find a two-mode operator which is responsible for complex fractional squeezing transformation. The entangled state representation and the Weyl ordering form of the two-mode Wigner operator are fully used in our derivation which brings convenience.
基金the financial support of LIN SB RAS state task No.0279-2021-0014performed under the partial support of PEEX programRFBR project № 20-55-12001 for support of aethalometrical measurements and data analyzing。
文摘Lake Baikal is the biggest reservoir of fresh water with unique flora and fauna;presently it is negatively affected by climate change, water warming, industrial emissions, shipping,touristic activities, and Siberian forest fires.The assessment of air pollution-related Baikal’s ecosystem damage is an unsolved problem.Ship, based expedition exploring the Baikal atmospheric aerosol loading, was performed over the lake area in July 2018.We combine the aerosol near-water and vertical distributions over the Lake Baikal basin with meteorological observations and air mass transportation simulations.Lidar sounding of aerosol fields in the troposphere assesses the atmospheric background in the pristine areas and the pollution during fire-affected periods.Aerosol optical properties(scattering and spectral absorption) converted to the particle number size, black carbon(BC) mass, and Absorption Angstrom Exponent(AAE) provide the inside into aerosol characterization.Transport of industrial emissions from Krasnoyarsk and Irkutsk regions, and wildfire plumes from Republic of Yakutia relates the pollution sources to the increased concentrations of fine particle numbers, PM_(10) and BC mass over Southern and Northern/Central Baikal, respectively.The highest PM10 and BC are associated to the harbor and touristic areas of intensive shipping and residential biomass burning.Deposition estimates applied to aerosol data exhibit the pollution fluxes to water surface over the whole Baikal area.AAE marks the impact of coal combustion, residential biomass burning, and wildfires indicating the high pollution level of the Lake Baikal ecological system.
文摘A new kind of lidar signal light-splitting system is presented to sum up different rotational Raman lines and to improve the signal to noise ratio(SNR) .The temperature parameters with high SNR of this new system have been obtained with a normal laser and a small telescope from several kilometers.
基金supported by the National Natural Science Foundation of China (Grant Nos. U20A2097,42075087, 91837310)the National Key Research and Development Program of China (Grant No. 2021YFC3000902)。
文摘Based on the TRMM dataset, this paper compares the applicability of the improved MCE(minimum circumscribed ellipse), MBR(minimum bounding rectangle), and DIA(direct indexing area) methods for rain cell fitting. These three methods can reflect the geometric characteristics of clouds and apply geometric parameters to estimate the real dimensions of rain cells. The MCE method shows a major advantage in identifying the circumference of rain cells. The circumference of rain cells identified by MCE in most samples is smaller than that identified by DIA and MBR, and more similar to the observed rain cells. The area of rain cells identified by MBR is relatively robust. For rain cells composed of many pixels(N> 20), the overall performance is better than that of MCE, but the contribution of MBR to the best identification results,which have the shortest circumference and the smallest area, is less than that of MCE. The DIA method is best suited to small rain cells with a circumference of less than 100 km and an area of less than 120 km^(2), but the overall performance is mediocre. The MCE method tends to achieve the highest success at any angle, whereas there are fewer “best identification”results from DIA or MBR and more of the worst ones in the along-track direction and cross-track direction. Through this comprehensive comparison, we conclude that MCE can obtain the best fitting results with the shortest circumference and the smallest area on behalf of the high filling effect for all sizes of rain cells.
基金the National Natural Science Foundation of China(No.61605223)the Strategic Priority Research Program of Chinese Academy of Sciences(Nos.306030105 and 614A010717)+1 种基金the Open Research Fund of State Key Laboratory of Pulsed Power Laser Technology(Nos.SKL2013KF01 and SKL2015KF03)the Dean Foundation of Hefei Institutes of Physical Science,Chinese Academy of Sciences(No.YZJJ201506).
文摘Cylindrical density depressions generated by femtosecond laser pulses filamenting in air for different energy depositions are investigated numerically, by using a set of hydrodynamic equations. The evolution of density profile is calculated for different temperature elevations. The results indicate that the gas density hole is getting shallower and wider with the increasing temperature elevations. A simulation of the propagation inside low-density channel implies a new way to generate a type of bottle beam.
文摘The paper introduces a new laser interferometry-based method for diagnosis of random media by means of high accuracy angle measurements and describes the results of its development and testing. Theoretical calculations of the dependence of the range of the laser interferometer on laser beam parameters, device geometry, and atmospheric turbulence characteristics are reported. It is demonstrated that at moderate turbulence intensities corresponding to those observed most frequently in turbulent atmosphere at moderate latitudes and with low interference contrast values, the performance range of the laser interferometer-based device exceeds 5 km.
文摘Lake Baikal is one of the most unique natural environments in Siberia, and it affects to a large extent the natural state in this region. Processes of gas exchange in the air-water system have been studied in Lake Baikal since 2002. Measurements have been carried out in the littoral area on the western shore of Southern Baikal (51°51'N, 105°04'E). The method of accumulative chambers was prioritized for measuring carbon dioxide fluxes in the air-water system. Chemical analysis of the water samples collected every three hours at the chamber locations was carried out in the on-land laboratory. We measured pH, content of dissolved oxygen, bicarbonate, nitrate and phosphate. The CO2 content in the water was measured from pH values and the bicarbonate concentration. The total sink of CO2 on the water surface is increasing in the littoral area of Lake Baikal from 20 mg·CO2·m-2·day-1 in June to 110 mg·CO2·m-2·day-1 in August. The decrease in the flux rate usually begins in September from 95 mg·CO2·m-2·day-1 to the zero balance in late October - early November. The maximal rate of mean diurnal CO2 emissions is recorded in December in the pre-ice period (110 mg·CO2·m-2·day-1). Based on the long-term measurements during all seasons, the sink of atmospheric CO2 in the littoral zones of Lake Baikal was estimated to be 3 - 5 g·CO2·m-2.
基金The authors would acknowledge financial support from the National Key Laboratory on Electromagnetic Environmental Effects and Electro-optical Engineering(NO.JCKYS2022LD6)the National Natural Science Foundation of China(42005068 and 42375074)+1 种基金the Project of Stable Support for Youth Team in Basic Research Field CAS(YSBR-018)the Joint Open Fund of Mengcheng National Geophysical Observatory(MENGO-202208).
文摘Narrow bipolar events(NBEs)are intriguing intra-cloud discharge that have attracted enormous interest in the lightning community.They come with two polarities that dominate at different altitudes in thunderclouds.The sources of negative NBEs are usually located near the top of thunderclouds;those of positive NBEs are at the middle levels.NBEs may occur at the onset of lightning.The electrical properties of NBEs remain poorly understood.We present here the first comparative study of the electrical characteristics of negative and positive NBEs.To derive electrical parameters from the fast electric field change waveforms of 1673 positive NBEs and 364 negative NBEs recorded by the Jianghuai Area Sferic Array(JASA)in China,we use an improved method based on the transmission line model.This approach concludes that negative NBEs occurring at high altitudes tend to produce a narrower current pulse and take a shorter time to traverse the channel than their positive counterparts.Moreover,compared to positive NBEs,a larger portion of negative NBEs are associated with slightly greater peak current moments but smaller overall charge moments.The differences reported herein between electrical properties of negative and positive NBEs suggest that charge distribution in NBE-producing thunderstorms tends to vary systematically with altitude.
