At 11:00 am on August 5, 2017, Cangyuan Washan Airport experienced low cloud and low visibility weather, accompanied by aircraft turbulence, which affected the normal operation of flights, which was closely related to...At 11:00 am on August 5, 2017, Cangyuan Washan Airport experienced low cloud and low visibility weather, accompanied by aircraft turbulence, which affected the normal operation of flights, which was closely related to the meteorological conditions at that time. Using the hourly reanalysis data of the European Centre for Medium-range Weather Forecast (ECMWF) Reanalysis 5 (ERA5), including Geopotential height, temperature, precipitation, wind field, specific humidity, vorticity and other elements, with a spatial resolution of 0.25° × 0.25°, this paper focuses on the horizontal distribution and vertical configuration of various physical quantities before and after the occurrence of low cloud and low visibility weather at the airport. The results indicate that the main influencing system of this low cloud and low visibility weather is the westward tropical depression. Before the occurrence of low cloud and low visibility weather, low-level water vapor converges and is accompanied by precipitation. The temperature decreases with precipitation, the near-surface wind direction changes, and the wind speed decreases.展开更多
A complex weather process at Shanghai Pudong International Airport during April 8-9 in 2017 was analyzed deeply to study the causes of low clouds and convective weather and how to provide services for control in the c...A complex weather process at Shanghai Pudong International Airport during April 8-9 in 2017 was analyzed deeply to study the causes of low clouds and convective weather and how to provide services for control in the complex weather situation. The results showed that when clouds and visibility were low,the situation of wind fields should be analyzed carefully to forecast the weather more accurately. The actual situation of the weather was in line with the numerical forecast on the day,and numerical forecast had certain reference value for convection forecast. The prediction of cloud height was not as perfect as expected on the day,but corresponding services were provided to the regulatory agencies 3 h early,and they had sufficient time to make decisions. The meteorological services have also been well received by the regulatory authorities,which further explains the importance of forecast in advance.展开更多
The concepts of “digital twins”, “3D real scene”, “metacosm” and others were the technical paths for building digital cities with the development of emerging surveying and mapping science and technology, which w...The concepts of “digital twins”, “3D real scene”, “metacosm” and others were the technical paths for building digital cities with the development of emerging surveying and mapping science and technology, which was to build a digital and virtualized city that matched the real physical world, to achieve a one-to-one correspondence between all elements of the physical world and the digital virtual world. And one of its basic geographic information data was a highly similar, virtual simulation of the 3D real scene. After exploring the traditional manual 3DsMax modeling, UAV low-altitude digital oblique photogrammetry modeling, airborne laser scanning modeling and other single modeling technologies, this paper discussed the 3D digital modeling technology used by the UAV airborne laser scanning point cloud and low-altitude digital oblique photogrammetry for complementary integration, constructing the 3D scene of the digital city. This paper expounded the technical route and production process of 3D digital modeling, in order to provide technical references for related projects.展开更多
Light Detection And Ranging (LiDAR) is a well-established active remote sensing technology that can provide accurate digital elevation measurements for the terrain and non-ground objects such as vegetations and buildi...Light Detection And Ranging (LiDAR) is a well-established active remote sensing technology that can provide accurate digital elevation measurements for the terrain and non-ground objects such as vegetations and buildings, etc. Non-ground objects need to be removed for creation of a Digital Terrain Model (DTM) which is a continuous surface representing only ground surface points. This study aimed at comparative analysis of three main filtering approaches for stripping off non-ground objects namely;Gaussian low pass filter, focal analysis mean filter and DTM slope-based filter of varying window sizes in creation of a reliable DTM from airborne LiDAR point clouds. A sample of LiDAR data provided by the ISPRS WG III/4 captured at Vaihingen in Germany over a pure residential area has been used in the analysis. Visual analysis has indicated that Gaussian low pass filter has given blurred DTMs of attenuated high-frequency objects and emphasized low-frequency objects while it has achieved improved removal of non-ground object at larger window sizes. Focal analysis mean filter has shown better removal of nonground objects compared to Gaussian low pass filter especially at large window sizes where details of non-ground objects almost have diminished in the DTMs from window sizes of 25 × 25 and greater. DTM slope-based filter has created bare earth models that have been full of gabs at the positions of the non-ground objects where the sizes and numbers of that gabs have increased with increasing the window sizes of filter. Those gaps have been closed through exploitation of the spline interpolation method in order to get continuous surface representing bare earth landscape. Comparative analysis has shown that the minimum elevations of the DTMs increase with increasing the filter widow sizes till 21 × 21 and 31 × 31 for the Gaussian low pass filter and the focal analysis mean filter respectively. On the other hand, the DTM slope-based filter has kept the minimum elevation of the original data, that could be due to noise i展开更多
Some observed results of NH3 (1, 1) and (2,2) line emission in the starless dark cloud L183 are reported. Our observation suggests that the dense core of L183 has a size of ~ 0.16pc x0.1pc with a mass of ~ 12M. A velo...Some observed results of NH3 (1, 1) and (2,2) line emission in the starless dark cloud L183 are reported. Our observation suggests that the dense core of L183 has a size of ~ 0.16pc x0.1pc with a mass of ~ 12M. A velocity gradient of 4km s-1 pc-1 from the north to the south was detected. The velocity shift corresponds to a central mass of ~ 5M . If it is caused by rotation, the mass would be much less than the value above. This suggests that there may be more mass in the envelope of L183 than in the central region. The analysis of our data and the evidence in the literature about L183 indicate that it may be undergoing a process of collapsing to form a low-mass binary dense core.展开更多
利用Micaps常规观测资料、NECP再分析资料和数值预报产品,采用天气学诊断分析方法对2015年8月3—4日河南省北部一次区域暴雨过程的形成机制进行分析。结果表明:该次暴雨过程是发生在深厚的蒙古低涡低槽前的上升运动区和700 h Pa切变线附...利用Micaps常规观测资料、NECP再分析资料和数值预报产品,采用天气学诊断分析方法对2015年8月3—4日河南省北部一次区域暴雨过程的形成机制进行分析。结果表明:该次暴雨过程是发生在深厚的蒙古低涡低槽前的上升运动区和700 h Pa切变线附近;副热带高压西侧西南急流为降水区提供了充足的水汽;地面辐合线为局地出现强对流天气提供了有利的辐合抬升和触发条件。垂直速度及其散度场等物理量对暴雨的发生有很好的指示意义,其演变可为暴雨的发生、发展以及落区、降水时段预报提供有力的预报依据。较大的降水出现在云团爆发性发展与合并时。"列车效应"导致豫北区域暴雨甚至大暴雨天气产生;逆风区的出现和冷平流的维持使得暴雨中出现短时强降水;细网格数值预报产品降水预报资料在该次降水预报中有较好的指示作用,对降水落区的把握有一定偏差。展开更多
文摘At 11:00 am on August 5, 2017, Cangyuan Washan Airport experienced low cloud and low visibility weather, accompanied by aircraft turbulence, which affected the normal operation of flights, which was closely related to the meteorological conditions at that time. Using the hourly reanalysis data of the European Centre for Medium-range Weather Forecast (ECMWF) Reanalysis 5 (ERA5), including Geopotential height, temperature, precipitation, wind field, specific humidity, vorticity and other elements, with a spatial resolution of 0.25° × 0.25°, this paper focuses on the horizontal distribution and vertical configuration of various physical quantities before and after the occurrence of low cloud and low visibility weather at the airport. The results indicate that the main influencing system of this low cloud and low visibility weather is the westward tropical depression. Before the occurrence of low cloud and low visibility weather, low-level water vapor converges and is accompanied by precipitation. The temperature decreases with precipitation, the near-surface wind direction changes, and the wind speed decreases.
文摘A complex weather process at Shanghai Pudong International Airport during April 8-9 in 2017 was analyzed deeply to study the causes of low clouds and convective weather and how to provide services for control in the complex weather situation. The results showed that when clouds and visibility were low,the situation of wind fields should be analyzed carefully to forecast the weather more accurately. The actual situation of the weather was in line with the numerical forecast on the day,and numerical forecast had certain reference value for convection forecast. The prediction of cloud height was not as perfect as expected on the day,but corresponding services were provided to the regulatory agencies 3 h early,and they had sufficient time to make decisions. The meteorological services have also been well received by the regulatory authorities,which further explains the importance of forecast in advance.
文摘The concepts of “digital twins”, “3D real scene”, “metacosm” and others were the technical paths for building digital cities with the development of emerging surveying and mapping science and technology, which was to build a digital and virtualized city that matched the real physical world, to achieve a one-to-one correspondence between all elements of the physical world and the digital virtual world. And one of its basic geographic information data was a highly similar, virtual simulation of the 3D real scene. After exploring the traditional manual 3DsMax modeling, UAV low-altitude digital oblique photogrammetry modeling, airborne laser scanning modeling and other single modeling technologies, this paper discussed the 3D digital modeling technology used by the UAV airborne laser scanning point cloud and low-altitude digital oblique photogrammetry for complementary integration, constructing the 3D scene of the digital city. This paper expounded the technical route and production process of 3D digital modeling, in order to provide technical references for related projects.
文摘Light Detection And Ranging (LiDAR) is a well-established active remote sensing technology that can provide accurate digital elevation measurements for the terrain and non-ground objects such as vegetations and buildings, etc. Non-ground objects need to be removed for creation of a Digital Terrain Model (DTM) which is a continuous surface representing only ground surface points. This study aimed at comparative analysis of three main filtering approaches for stripping off non-ground objects namely;Gaussian low pass filter, focal analysis mean filter and DTM slope-based filter of varying window sizes in creation of a reliable DTM from airborne LiDAR point clouds. A sample of LiDAR data provided by the ISPRS WG III/4 captured at Vaihingen in Germany over a pure residential area has been used in the analysis. Visual analysis has indicated that Gaussian low pass filter has given blurred DTMs of attenuated high-frequency objects and emphasized low-frequency objects while it has achieved improved removal of non-ground object at larger window sizes. Focal analysis mean filter has shown better removal of nonground objects compared to Gaussian low pass filter especially at large window sizes where details of non-ground objects almost have diminished in the DTMs from window sizes of 25 × 25 and greater. DTM slope-based filter has created bare earth models that have been full of gabs at the positions of the non-ground objects where the sizes and numbers of that gabs have increased with increasing the window sizes of filter. Those gaps have been closed through exploitation of the spline interpolation method in order to get continuous surface representing bare earth landscape. Comparative analysis has shown that the minimum elevations of the DTMs increase with increasing the filter widow sizes till 21 × 21 and 31 × 31 for the Gaussian low pass filter and the focal analysis mean filter respectively. On the other hand, the DTM slope-based filter has kept the minimum elevation of the original data, that could be due to noise i
文摘Some observed results of NH3 (1, 1) and (2,2) line emission in the starless dark cloud L183 are reported. Our observation suggests that the dense core of L183 has a size of ~ 0.16pc x0.1pc with a mass of ~ 12M. A velocity gradient of 4km s-1 pc-1 from the north to the south was detected. The velocity shift corresponds to a central mass of ~ 5M . If it is caused by rotation, the mass would be much less than the value above. This suggests that there may be more mass in the envelope of L183 than in the central region. The analysis of our data and the evidence in the literature about L183 indicate that it may be undergoing a process of collapsing to form a low-mass binary dense core.
文摘利用Micaps常规观测资料、NECP再分析资料和数值预报产品,采用天气学诊断分析方法对2015年8月3—4日河南省北部一次区域暴雨过程的形成机制进行分析。结果表明:该次暴雨过程是发生在深厚的蒙古低涡低槽前的上升运动区和700 h Pa切变线附近;副热带高压西侧西南急流为降水区提供了充足的水汽;地面辐合线为局地出现强对流天气提供了有利的辐合抬升和触发条件。垂直速度及其散度场等物理量对暴雨的发生有很好的指示意义,其演变可为暴雨的发生、发展以及落区、降水时段预报提供有力的预报依据。较大的降水出现在云团爆发性发展与合并时。"列车效应"导致豫北区域暴雨甚至大暴雨天气产生;逆风区的出现和冷平流的维持使得暴雨中出现短时强降水;细网格数值预报产品降水预报资料在该次降水预报中有较好的指示作用,对降水落区的把握有一定偏差。
