The macro and micro cloud physics structures and their evolution with time are the core of describing cloud fields in essence.They are necessary atmospheric environment not only in aviation and spaceflight activities ...The macro and micro cloud physics structures and their evolution with time are the core of describing cloud fields in essence.They are necessary atmospheric environment not only in aviation and spaceflight activities but also for atmos- pheric radiation transfer and acid rain formation research.Unfortunately it is difficult to obtain an entire environmental cloud field by using observation methods directly.Thus,by use of computation physics method to build a cloud-system model may be an indispensable way for this topic.This paper presented a cloud-system model for this goal,and simu- lated a real case.The results of computation showed that the macro structure of the cloud field was better consistent with real observation,and the micro structure was fairly reasonable.The output of model could provide all the information about the cloud field:(1)size-distribution spectrum of hydrometeor particles (point),(2)vertical profile (line),(3)hori- zontal or vertical section of macro and micro parameters (surface),and (4)cloud cover,pattern of cloud and configura- tion of cloud,etc.(body).展开更多
The purpose of this paper is to explore the effect of magnetic fields on the dynamics of magnetized filamentary molecular clouds. We suppose there is a filament with cylindrical symmetry and two components of axial an...The purpose of this paper is to explore the effect of magnetic fields on the dynamics of magnetized filamentary molecular clouds. We suppose there is a filament with cylindrical symmetry and two components of axial and toroidal magnetic fields. In comparison to previous works, the novelty in the present work involves a similarity solution that does not define a function of the magnetic fields or density. We consider the effect of the magnetic field on the collapse of the filament in both axial and toroidal directions and show that the magnetic field has a braking effect, which means that the increasing intensity of the magnetic field reduces the velocity of collapse. This is consistent with other studies. We find that the magnetic field in the central region tends to be aligned with the filament axis. Also, the magnitude and the direction of the magnetic field depend on the magnitude and direction of the initial magnetic field in the outer region. Moreover, we show that more energy dissipation from the filament causes a rise in the infall velocity.展开更多
Based on the fast algorithm of meteorological satellite guide wind vector tracing, cloud motion wind vector is calculated. According to the different characteristics of cloud motion wind field and sounding wind field,...Based on the fast algorithm of meteorological satellite guide wind vector tracing, cloud motion wind vector is calculated. According to the different characteristics of cloud motion wind field and sounding wind field, a method which fuses conventional data with unconventional data based on variation principle is presented. The fundamental is constructing a cost function that makes the value approach conventional data and the gradient approach unconventional data. Using this method, the conventional wind and the cloud motion wind are fused. The fused wind field has high resolu- tion. Its wind direction approaches cloud motion wind which indicates move direction of the synoptic system, and its velocity approaches conventional wind which indicates move velocity of the synoptic system. The wind field data are used for short-time forecast of severe convective weather location, which gets a good result.展开更多
In order to overcome the disadvantages of low accuracy rate, high complexity and poor robustness to image noise in many traditional algorithms of cloud image detection, this paper proposed a novel algorithm on the bas...In order to overcome the disadvantages of low accuracy rate, high complexity and poor robustness to image noise in many traditional algorithms of cloud image detection, this paper proposed a novel algorithm on the basis of Markov Random Field (MRF) modeling. This paper first defined algorithm model and derived the core factors affecting the performance of the algorithm, and then, the solving of this algorithm was obtained by the use of Belief Propagation (BP) algorithm and Iterated Conditional Modes (ICM) algorithm. Finally, experiments indicate that this algorithm for the cloud image detection has higher average accuracy rate which is about 98.76% and the average result can also reach 96.92% for different type of image noise.展开更多
The state of the physics of convective clouds and cloud seeding is discussed briefly. It is noted that at the present time there is a transition from the stage of investigation of “elementary” processes in the cloud...The state of the physics of convective clouds and cloud seeding is discussed briefly. It is noted that at the present time there is a transition from the stage of investigation of “elementary” processes in the clouds to the stage of studying the formation of macro- and microstructural characteristics of clouds as a whole, taking into account their system properties. The main directions of the development of cloud physics at the upcoming stage of its development are discussed. The paper points out that one of these areas is the determination of the structure-forming factors for the clouds and the study of their influence on their formation and evolution. It is noted that one of such factors is the interaction of clouds with their surrounding atmosphere, and the main method of studying its role in the processes of cloud formation is mathematical modeling. A three-dimensional nonstationary model of convective clouds is presented with a detailed account of the processes of thermohydrodynamics and microphysics, which is used for research. The results of modeling the influence of the wind field structure in the atmosphere on the formation and evolution of clouds are presented. It is shown that the dynamic characteristics of the atmosphere have a significant effect on the formation of macro- and microstructural characteristics of convective clouds: the more complex the structure of the wind field in the atmosphere (i.e., the more intense the interaction of the atmosphere and the cloud), the less powerful the clouds are formed.展开更多
A prototype space-based cloud radar has been a precipitation system over Tianjin, China in July developed and was installed on an airplane to observe 2010. Ground-based S-band and Ka-band radars were used to examine t...A prototype space-based cloud radar has been a precipitation system over Tianjin, China in July developed and was installed on an airplane to observe 2010. Ground-based S-band and Ka-band radars were used to examine the observational capability of the prototype. A cross-comparison algorithm between different wavelengths, spatial resolutions and platform radars is presented. The reflectivity biases, correlation coefficients and standard deviations between the radars are analyzed. The equivalent reflectivity bias between the S- and Ka-band radars were simulated with a given raindrop size distribution. The results indicated that reflectivity bias between the S- and Ka-band radars due to scattering properties was less than 5 dB, and for weak precipitation the bias was negligible. The prototype space-based cloud radar was able to measure a reasonable vertical profile of reflectivity, but the reflectivity below an altitude of 1.5 km above ground level was obscured by ground clutter. The measured refiectivity by the prototype space-based cloud radar was approximately 10.9 dB stronger than that by the S-band Doppler radar （SA radar）, and 13.7 dB stronger than that by the ground-based cloud radar. The reflectivity measured by the SA radar was 0.4 dB stronger than that by the ground-based cloud radar. This study could provide a method for the quantitative examination of the observation ability for space-based radars.展开更多
A three-dimensional wind field analysis sollware based on the Beigng-Gucheng dual-Doppler weather radar system has been built, and evaluated by using the numerical cloud model producing storm flow and hydrometeor fiel...A three-dimensional wind field analysis sollware based on the Beigng-Gucheng dual-Doppler weather radar system has been built, and evaluated by using the numerical cloud model producing storm flow and hydrometeor fields. The effects of observation noise and the spatial distribution of wind field analysis error are also investigated.展开更多
In this paper, we present the critical mass of magnetized, turbulent and rotating star-forming molecular cloud core (MCc) in the presence of magnetic tension. The critical mass of star-forming magnetized cloud is infl...In this paper, we present the critical mass of magnetized, turbulent and rotating star-forming molecular cloud core (MCc) in the presence of magnetic tension. The critical mass of star-forming magnetized cloud is influenced by the magnetic tension, magnetic pressure and other pressures. Applying the method of theoretical modelling by taking into account the basic equations and assumptions, we formulate the critical mass of magnetized MCc in different cases. Accordingly, the minimum critical masses we find in both cases are different. Energy due to magnetic tension significantly triggers the collapse at relatively larger radius of the core. The model shows that when the initial radius of the parent cloud (Ro) is larger than that of collapsing core radius (Rcore) the magnetic tension also has the larger radius of curvature, so it plays a significant role in supporting gravity to collapse the core. The results indicate gravity without magnetic tension may not overcome magnetic pressure, turbulence pressure and pressure due to rotation. This shows the critical mass of MCc for the collapse depends on the tension force that magnetic field lines apply on the envelope. We conclude that if there is magnetic pressure in star-forming MCc, there is also unavoidable magnetic tension, which triggers the collapse of the core. If there is no magnetic tension, the magnetized MCc needs relatively larger mass and higher density within the small size to collapse.展开更多
The 80 high-mass X-ray binary （HMXB） pulsars that are known to reside in the Magellanic Clouds （MCs） have been observed by the XMM-Newton and Chandra X-ray telescopes on a regular basis for 15 years, and the XMM-N...The 80 high-mass X-ray binary （HMXB） pulsars that are known to reside in the Magellanic Clouds （MCs） have been observed by the XMM-Newton and Chandra X-ray telescopes on a regular basis for 15 years, and the XMM-Newton and Chandra archives contain nearly complete information about the duty cycles of the sources with spin periods Ps 〈 100 s. We have reprocessed the archival data from both observatories and we combined the output products with all the published observations of 31 MC pulsars with Ps 〈 100 s in an attempt to investigate the faintest X-ray emission states of these objects that occur when accretion to the polar caps proceeds at the smallest possible rates. These states determine the so-called propeller lines of the accreting pulsars and yield information about the magnitudes of their surface magnetic fields. We have found that the faintest states of the pulsars segregate into five discrete groups which obey to a high degree of accuracy the theoretical relation between spin period and X-ray luminosity. So the entire population of these pulsars can be described by just five propeller lines and the five corresponding magnetic moments （0.29, 0.53, 1.2, 2.9 and 7.3, in units of 1030 G cma）.展开更多
在地球观测领域,航空光学影像和机载激光探测与测距(light detection and ranging,LiDAR)点云是获取地表空间信息的主要数据源。精确的几何配准是融合这两类数据的前提。本文提出了一种像方距离场与物方平面约束联合的航空影像与激光点...在地球观测领域,航空光学影像和机载激光探测与测距(light detection and ranging,LiDAR)点云是获取地表空间信息的主要数据源。精确的几何配准是融合这两类数据的前提。本文提出了一种像方距离场与物方平面约束联合的航空影像与激光点云精确配准方法。该方法分为基于线元距离场的单像配准和线面约束结合的区域网平差两个阶段。在基于线元距离场的单像配准中,首先从航空影像和机载LiDAR点云中分别提取线元素,然后基于航空影像线元素构建距离场,并将点云线基元投影至像平面。通过渐进式稳健求解最小化点云投影线基元在距离场中的全局代价,从而实现单张影像与LiDAR点云的配准。在线面约束结合的区域网平差阶段,选择部分线特征分布较为密集的影像作为关键景影像,并对关键景影像中的同名线元素进行匹配,以提取控制点作为水平及高程约束。此外,还利用影像连接点到最近水平面的距离作为高程约束,通过区域网平差实现多视航空影像与机载点云的配准。试验结果表明,该方法能在初始值较差的情况下实现稳健配准,其配准精度优于点云间距,配准精度与配准效率都显著优于迭代最近点(iterative closest point,ICP)配准算法和通过跨模态匹配进行配准的策略。展开更多
基金the National Natural Science Foundation of China State Key Projects for Science and Technology during the 8th Five-Year Plan 85906-04-03
文摘The macro and micro cloud physics structures and their evolution with time are the core of describing cloud fields in essence.They are necessary atmospheric environment not only in aviation and spaceflight activities but also for atmos- pheric radiation transfer and acid rain formation research.Unfortunately it is difficult to obtain an entire environmental cloud field by using observation methods directly.Thus,by use of computation physics method to build a cloud-system model may be an indispensable way for this topic.This paper presented a cloud-system model for this goal,and simu- lated a real case.The results of computation showed that the macro structure of the cloud field was better consistent with real observation,and the micro structure was fairly reasonable.The output of model could provide all the information about the cloud field:(1)size-distribution spectrum of hydrometeor particles (point),(2)vertical profile (line),(3)hori- zontal or vertical section of macro and micro parameters (surface),and (4)cloud cover,pattern of cloud and configura- tion of cloud,etc.(body).
文摘The purpose of this paper is to explore the effect of magnetic fields on the dynamics of magnetized filamentary molecular clouds. We suppose there is a filament with cylindrical symmetry and two components of axial and toroidal magnetic fields. In comparison to previous works, the novelty in the present work involves a similarity solution that does not define a function of the magnetic fields or density. We consider the effect of the magnetic field on the collapse of the filament in both axial and toroidal directions and show that the magnetic field has a braking effect, which means that the increasing intensity of the magnetic field reduces the velocity of collapse. This is consistent with other studies. We find that the magnetic field in the central region tends to be aligned with the filament axis. Also, the magnitude and the direction of the magnetic field depend on the magnitude and direction of the initial magnetic field in the outer region. Moreover, we show that more energy dissipation from the filament causes a rise in the infall velocity.
文摘Based on the fast algorithm of meteorological satellite guide wind vector tracing, cloud motion wind vector is calculated. According to the different characteristics of cloud motion wind field and sounding wind field, a method which fuses conventional data with unconventional data based on variation principle is presented. The fundamental is constructing a cost function that makes the value approach conventional data and the gradient approach unconventional data. Using this method, the conventional wind and the cloud motion wind are fused. The fused wind field has high resolu- tion. Its wind direction approaches cloud motion wind which indicates move direction of the synoptic system, and its velocity approaches conventional wind which indicates move velocity of the synoptic system. The wind field data are used for short-time forecast of severe convective weather location, which gets a good result.
基金Supported by the National Natural Science Foundation of China (No. 61172047)
文摘In order to overcome the disadvantages of low accuracy rate, high complexity and poor robustness to image noise in many traditional algorithms of cloud image detection, this paper proposed a novel algorithm on the basis of Markov Random Field (MRF) modeling. This paper first defined algorithm model and derived the core factors affecting the performance of the algorithm, and then, the solving of this algorithm was obtained by the use of Belief Propagation (BP) algorithm and Iterated Conditional Modes (ICM) algorithm. Finally, experiments indicate that this algorithm for the cloud image detection has higher average accuracy rate which is about 98.76% and the average result can also reach 96.92% for different type of image noise.
文摘The state of the physics of convective clouds and cloud seeding is discussed briefly. It is noted that at the present time there is a transition from the stage of investigation of “elementary” processes in the clouds to the stage of studying the formation of macro- and microstructural characteristics of clouds as a whole, taking into account their system properties. The main directions of the development of cloud physics at the upcoming stage of its development are discussed. The paper points out that one of these areas is the determination of the structure-forming factors for the clouds and the study of their influence on their formation and evolution. It is noted that one of such factors is the interaction of clouds with their surrounding atmosphere, and the main method of studying its role in the processes of cloud formation is mathematical modeling. A three-dimensional nonstationary model of convective clouds is presented with a detailed account of the processes of thermohydrodynamics and microphysics, which is used for research. The results of modeling the influence of the wind field structure in the atmosphere on the formation and evolution of clouds are presented. It is shown that the dynamic characteristics of the atmosphere have a significant effect on the formation of macro- and microstructural characteristics of convective clouds: the more complex the structure of the wind field in the atmosphere (i.e., the more intense the interaction of the atmosphere and the cloud), the less powerful the clouds are formed.
基金the Chinese Academy of Meteorological Sciences Basic Scientific and Operational Project(observation and retrieval methods of microphysics and dynamic parameters of cloud and precipitation with multi-wavelength remote sensing)the National Key Program for Developing Basic Sciences under Grant 2012CB417202+1 种基金the Meteorological Special Project(study and data process and key technology for space-borne precipitation radar)the National Natural Science Foundation of China(Grant Nos.40775021 and 41075098)
文摘A prototype space-based cloud radar has been a precipitation system over Tianjin, China in July developed and was installed on an airplane to observe 2010. Ground-based S-band and Ka-band radars were used to examine the observational capability of the prototype. A cross-comparison algorithm between different wavelengths, spatial resolutions and platform radars is presented. The reflectivity biases, correlation coefficients and standard deviations between the radars are analyzed. The equivalent reflectivity bias between the S- and Ka-band radars were simulated with a given raindrop size distribution. The results indicated that reflectivity bias between the S- and Ka-band radars due to scattering properties was less than 5 dB, and for weak precipitation the bias was negligible. The prototype space-based cloud radar was able to measure a reasonable vertical profile of reflectivity, but the reflectivity below an altitude of 1.5 km above ground level was obscured by ground clutter. The measured refiectivity by the prototype space-based cloud radar was approximately 10.9 dB stronger than that by the S-band Doppler radar （SA radar）, and 13.7 dB stronger than that by the ground-based cloud radar. The reflectivity measured by the SA radar was 0.4 dB stronger than that by the ground-based cloud radar. This study could provide a method for the quantitative examination of the observation ability for space-based radars.
文摘A three-dimensional wind field analysis sollware based on the Beigng-Gucheng dual-Doppler weather radar system has been built, and evaluated by using the numerical cloud model producing storm flow and hydrometeor fields. The effects of observation noise and the spatial distribution of wind field analysis error are also investigated.
文摘In this paper, we present the critical mass of magnetized, turbulent and rotating star-forming molecular cloud core (MCc) in the presence of magnetic tension. The critical mass of star-forming magnetized cloud is influenced by the magnetic tension, magnetic pressure and other pressures. Applying the method of theoretical modelling by taking into account the basic equations and assumptions, we formulate the critical mass of magnetized MCc in different cases. Accordingly, the minimum critical masses we find in both cases are different. Energy due to magnetic tension significantly triggers the collapse at relatively larger radius of the core. The model shows that when the initial radius of the parent cloud (Ro) is larger than that of collapsing core radius (Rcore) the magnetic tension also has the larger radius of curvature, so it plays a significant role in supporting gravity to collapse the core. The results indicate gravity without magnetic tension may not overcome magnetic pressure, turbulence pressure and pressure due to rotation. This shows the critical mass of MCc for the collapse depends on the tension force that magnetic field lines apply on the envelope. We conclude that if there is magnetic pressure in star-forming MCc, there is also unavoidable magnetic tension, which triggers the collapse of the core. If there is no magnetic tension, the magnetized MCc needs relatively larger mass and higher density within the small size to collapse.
文摘The 80 high-mass X-ray binary （HMXB） pulsars that are known to reside in the Magellanic Clouds （MCs） have been observed by the XMM-Newton and Chandra X-ray telescopes on a regular basis for 15 years, and the XMM-Newton and Chandra archives contain nearly complete information about the duty cycles of the sources with spin periods Ps 〈 100 s. We have reprocessed the archival data from both observatories and we combined the output products with all the published observations of 31 MC pulsars with Ps 〈 100 s in an attempt to investigate the faintest X-ray emission states of these objects that occur when accretion to the polar caps proceeds at the smallest possible rates. These states determine the so-called propeller lines of the accreting pulsars and yield information about the magnitudes of their surface magnetic fields. We have found that the faintest states of the pulsars segregate into five discrete groups which obey to a high degree of accuracy the theoretical relation between spin period and X-ray luminosity. So the entire population of these pulsars can be described by just five propeller lines and the five corresponding magnetic moments （0.29, 0.53, 1.2, 2.9 and 7.3, in units of 1030 G cma）.
文摘目的 基于点云的神经渲染方法受点云质量及特征提取的影响,易导致新视角合成图像渲染质量下降,为此提出一种融合局部空间信息的新视角合成方法。方法 针对点云质量及提取特征不足的问题,首先,设计一种神经点云特征对齐模块,将点云与图像匹配区域的特征进行对齐,融合后构成神经点云,提升其特征的局部表达能力;其次,提出一种神经点云Transformer模块,用于融合局部神经点云的上下文信息,在点云质量不佳的情况下仍能提取可靠的局部空间信息,有效增强了点云神经渲染方法的合成质量。结果 实验结果表明,在真实场景数据集中,对于只包含单一物品的数据集Tanks and Temples,本文方法在峰值信噪比(peak signal to noise ratio,PSNR)指标上与NeRF(neural radiance field)方法相比提升19.2%,相较于使用点云输入的方法 Tetra-NeRF和Point-NeRF分别提升了6.4%和3.8%,即使在场景更为复杂的ScanNet数据集中,与NeRF方法及Point-NeRF相比分别提升了34.6%和2.1%。结论 本文方法能够更好地利用点云的局部空间信息,有效改善了稀疏视角图像输入下因点云质量和提取特征导致的渲染质量下降,实验结果验证了本文方法的有效性。
