A precipitation enhancement operation using an aircraft was conducted from 1415 to 1549 LST 14 March 2000 in Shaanxi Province. The NOAA-14 satellite data received at 1535 LST soon after the cloud seeding shows that a ...A precipitation enhancement operation using an aircraft was conducted from 1415 to 1549 LST 14 March 2000 in Shaanxi Province. The NOAA-14 satellite data received at 1535 LST soon after the cloud seeding shows that a vivid cloud track appears on the satellite image. The length, average width and maximum width of the cloud track are 301 km, 8.3 and 11 km, respectively. Using a three-dimensional numerical model of transport and diffusion of seeding material within stratiform clouds, the spatial concentration distribution characteristics of seeding material at different times, especially at the satellite receiving time, are simulated. The model results at the satellite receiving time are compared with the features of the cloud track. The transported position of the cloud seeding material coincides with the position of the track. The width, shape and extent of diffusion of the cloud seeding material are similar to that of the cloud track. The spatial variation of width is consistent with that of the track. The simulated length of each segment of the seeding line accords with the length of every segment of the track. Each segment of the cloud track corresponds to the transport and diffusion of each segment of the seeding line. These results suggest that the cloud track is the direct physical reflection of cloud seeding at the cloud top. The comparison demonstrates that the numerical model of transport and diffusion can simulate the main characteristics of transport and diffusion of seeding material, and the simulated results are sound and trustworthy. The area, volume, vidth, depth, and lateral diffusive rate corresponding to concentrations 1, 4, and 10 L-1are simulated in order to understand the variations of influencing range.展开更多
Despite the multifaceted advantages of cloud computing,concerns about data leakage or abuse impedes its adoption for security-sensi tive tasks.Recent investigations have revealed that the risk of unauthorized data acc...Despite the multifaceted advantages of cloud computing,concerns about data leakage or abuse impedes its adoption for security-sensi tive tasks.Recent investigations have revealed that the risk of unauthorized data access is one of the biggest concerns of users of cloud-based services.Transparency and accountability for data managed in the cloud is necessary.Specifically,when using a cloudhost service,a user typically has to trust both the cloud service provider and cloud infrastructure provider to properly handling private data.This is a multi-party system.Three particular trust models can be used according to the credibility of these providers.This pa per describes techniques for preventing data leakage that can be used with these different models.展开更多
Previous satellite observations have identified the appearance of“cloud trough”(or“cloud trench”),with cloud tops visually collapsed following airborne cloud seeding operation,demonstrating the effect of weather m...Previous satellite observations have identified the appearance of“cloud trough”(or“cloud trench”),with cloud tops visually collapsed following airborne cloud seeding operation,demonstrating the effect of weather modification.However,refined observations of troughed clouds and associated microphysical processes are still notably scarce,especially those obtained via in-situ aircraft measurements.In this study,variations in cloud microphysics associated with and without troughed clouds along an airborne stratiform cloud seeding path over central China on 15 December 2019 are analyzed and compared based on aircraft measurements,ground-based radar observations,and FY-4A satellite imagery.The results are as follows.(1)The troughed clouds were mainly formed to the northeast of the flight path and were observed only in some parts of the seeded stratiform clouds.The seeding tracks became visible starting from 60 min after seeding and persisted for approximately 3 h,covering a maximum width of 30–40 km in FY-4A imagery.Radar echo enhancements can be observed by a ground-based radar at some parts of the seeding tracks.(2)The troughed clouds were observed only when the ambient air temperature(T)was≤-7℃,a condition favoring high nucleation efficiency of silver iodide(Ag I)aerosols,whereas no cloud troughs formed at higher temperatures.(3)The troughed clouds with strong radar echoes(i.e.,large precipitation)corresponded to regions with high values(>0.1 g m^(-3))of supercooled water content after cloud seeding,which facilitated the growth of precipitation particles.(4)Within the troughed clouds,the cloud optical thickness and cloud top height decreased,while the effective radii of cloud particles increased by nearly 10μm.These results provide valuable guidance for optimizing cold cloud seeding conditions in artificial rainfall enhancement.Meanwhile,the presence of high supercooled water content,particularly the threshold of supercooled water content,is a critical factor for strong precipitation,which necessitates further studies.展开更多
Based on the satellite retrieval methodology, the spectral characteristics and cloud microphysical properties were analyzed that included brightness temperatures of Channels 4 and 5, and their brightness temperature d...Based on the satellite retrieval methodology, the spectral characteristics and cloud microphysical properties were analyzed that included brightness temperatures of Channels 4 and 5, and their brightness temperature difference （BTD）, the particle effective radius of seeded cloud track caused by an operational cloud seeding and the microphysical effects of cloud seeding were revealed by the comparisons of their differences inside and outside the seeded track. The cloud track was actually a cloud channel reaching 1.5-km deep and 14-km wide lasting for more than 80 min. The effective radius of ambient clouds was 10-15 μm, while that within the cloud track ranged from 15 to 26 μm. The ambient clouds were composed of supercooled droplets, and the composition of the cloud within the seeding track was ice. With respect to the rather stable reflectance of two ambient sides around the track, the visible spectral reflectance in the cloud track varied at least 10%, and reached a maximum of 35%, the reflectance of 3.7 μm in the seeded track relatively decreased at least 10%. As cloud seeding advanced, the width and depth were gradually increased. Simultaneously the cloud top temperature within the track became progressively warmer with respect to the ambient clouds, and the maximum temperature differences reached 4.2 and 3.9℃ at the first seeding position for Channels 4 and 5. In addition, the BTD in the track also increased steadily to a maximum of 1.4℃, compared with 0.2-0.4℃ of the ambient clouds. The evidence that the seeded cloud became thinner comes from the visible image showing a channel, the warming of the cloud tops, and the increase of BTD in the seeded track. The seeded cloud became thinner mainly because the cloud top descended and it lost water to precipitation throughout its depth. For this cloud seeding case, the glaciation became apparent at cloud tops about 22 min after seeding. The formation of a cloud track in the supercooled stratiform clouds was mainly because that the seeded cloud volume glaciated into ice hydrometeors that precipitated and so lowered cloud top height. A thin line of new water clouds formed in the middle of the seeded track between 38 and 63 min after seeding, probably as a result of rising motion induced by the released latent heat of freezing. These clouds disappeared in the earlier segments of the seeded track, which suggested that the maturation of the seeding track was associated with its narrowing and eventual dissipation due to expansion of the tops of the ambient clouds from the sides inward.展开更多
文摘A precipitation enhancement operation using an aircraft was conducted from 1415 to 1549 LST 14 March 2000 in Shaanxi Province. The NOAA-14 satellite data received at 1535 LST soon after the cloud seeding shows that a vivid cloud track appears on the satellite image. The length, average width and maximum width of the cloud track are 301 km, 8.3 and 11 km, respectively. Using a three-dimensional numerical model of transport and diffusion of seeding material within stratiform clouds, the spatial concentration distribution characteristics of seeding material at different times, especially at the satellite receiving time, are simulated. The model results at the satellite receiving time are compared with the features of the cloud track. The transported position of the cloud seeding material coincides with the position of the track. The width, shape and extent of diffusion of the cloud seeding material are similar to that of the cloud track. The spatial variation of width is consistent with that of the track. The simulated length of each segment of the seeding line accords with the length of every segment of the track. Each segment of the cloud track corresponds to the transport and diffusion of each segment of the seeding line. These results suggest that the cloud track is the direct physical reflection of cloud seeding at the cloud top. The comparison demonstrates that the numerical model of transport and diffusion can simulate the main characteristics of transport and diffusion of seeding material, and the simulated results are sound and trustworthy. The area, volume, vidth, depth, and lateral diffusive rate corresponding to concentrations 1, 4, and 10 L-1are simulated in order to understand the variations of influencing range.
基金supported by National Basic Research (973) Program of China (2011CB302505)Natural Science Foundation of China (61373145, 61170210)+1 种基金National High-Tech R&D (863) Program of China (2012AA012600,2011AA01A203)Chinese Special Project of Science and Technology (2012ZX01039001)
文摘Despite the multifaceted advantages of cloud computing,concerns about data leakage or abuse impedes its adoption for security-sensi tive tasks.Recent investigations have revealed that the risk of unauthorized data access is one of the biggest concerns of users of cloud-based services.Transparency and accountability for data managed in the cloud is necessary.Specifically,when using a cloudhost service,a user typically has to trust both the cloud service provider and cloud infrastructure provider to properly handling private data.This is a multi-party system.Three particular trust models can be used according to the credibility of these providers.This pa per describes techniques for preventing data leakage that can be used with these different models.
基金Supported by the Key Science and Technology Project of Henan Province(252102321006 and 242102320037)Henan Key Laboratory of Agrometeorological Safeguard Application Techniques(KM202220,KQ202022,and KQ202425)+2 种基金Fengyun Application Pioneer-ing Project(20220111)Central Regional Weather Modification Capacity Building Project of China Meteorological Administration,Weather Modification Research Experiment in Danjiangkou Reservoir(ZQC-H22255)Research Experiment on Rain&Snow Enhancement Through Cloud Seeding in Stratiform Clouds with Embedded Convection in Central China(Shangqiu)(ZQC-H22256)。
文摘Previous satellite observations have identified the appearance of“cloud trough”(or“cloud trench”),with cloud tops visually collapsed following airborne cloud seeding operation,demonstrating the effect of weather modification.However,refined observations of troughed clouds and associated microphysical processes are still notably scarce,especially those obtained via in-situ aircraft measurements.In this study,variations in cloud microphysics associated with and without troughed clouds along an airborne stratiform cloud seeding path over central China on 15 December 2019 are analyzed and compared based on aircraft measurements,ground-based radar observations,and FY-4A satellite imagery.The results are as follows.(1)The troughed clouds were mainly formed to the northeast of the flight path and were observed only in some parts of the seeded stratiform clouds.The seeding tracks became visible starting from 60 min after seeding and persisted for approximately 3 h,covering a maximum width of 30–40 km in FY-4A imagery.Radar echo enhancements can be observed by a ground-based radar at some parts of the seeding tracks.(2)The troughed clouds were observed only when the ambient air temperature(T)was≤-7℃,a condition favoring high nucleation efficiency of silver iodide(Ag I)aerosols,whereas no cloud troughs formed at higher temperatures.(3)The troughed clouds with strong radar echoes(i.e.,large precipitation)corresponded to regions with high values(>0.1 g m^(-3))of supercooled water content after cloud seeding,which facilitated the growth of precipitation particles.(4)Within the troughed clouds,the cloud optical thickness and cloud top height decreased,while the effective radii of cloud particles increased by nearly 10μm.These results provide valuable guidance for optimizing cold cloud seeding conditions in artificial rainfall enhancement.Meanwhile,the presence of high supercooled water content,particularly the threshold of supercooled water content,is a critical factor for strong precipitation,which necessitates further studies.
基金the National Natural Science Foundation of China under Grant No. 40575004the Chinese Ministry of Science and Technology (Grant 2005DIB3J099).
文摘Based on the satellite retrieval methodology, the spectral characteristics and cloud microphysical properties were analyzed that included brightness temperatures of Channels 4 and 5, and their brightness temperature difference （BTD）, the particle effective radius of seeded cloud track caused by an operational cloud seeding and the microphysical effects of cloud seeding were revealed by the comparisons of their differences inside and outside the seeded track. The cloud track was actually a cloud channel reaching 1.5-km deep and 14-km wide lasting for more than 80 min. The effective radius of ambient clouds was 10-15 μm, while that within the cloud track ranged from 15 to 26 μm. The ambient clouds were composed of supercooled droplets, and the composition of the cloud within the seeding track was ice. With respect to the rather stable reflectance of two ambient sides around the track, the visible spectral reflectance in the cloud track varied at least 10%, and reached a maximum of 35%, the reflectance of 3.7 μm in the seeded track relatively decreased at least 10%. As cloud seeding advanced, the width and depth were gradually increased. Simultaneously the cloud top temperature within the track became progressively warmer with respect to the ambient clouds, and the maximum temperature differences reached 4.2 and 3.9℃ at the first seeding position for Channels 4 and 5. In addition, the BTD in the track also increased steadily to a maximum of 1.4℃, compared with 0.2-0.4℃ of the ambient clouds. The evidence that the seeded cloud became thinner comes from the visible image showing a channel, the warming of the cloud tops, and the increase of BTD in the seeded track. The seeded cloud became thinner mainly because the cloud top descended and it lost water to precipitation throughout its depth. For this cloud seeding case, the glaciation became apparent at cloud tops about 22 min after seeding. The formation of a cloud track in the supercooled stratiform clouds was mainly because that the seeded cloud volume glaciated into ice hydrometeors that precipitated and so lowered cloud top height. A thin line of new water clouds formed in the middle of the seeded track between 38 and 63 min after seeding, probably as a result of rising motion induced by the released latent heat of freezing. These clouds disappeared in the earlier segments of the seeded track, which suggested that the maturation of the seeding track was associated with its narrowing and eventual dissipation due to expansion of the tops of the ambient clouds from the sides inward.
