This study investigates the cloud macro-and micro-physical characteristics in the convective and stratiform regions and their different responses to the seeding for mixed convective-stratiform clouds that occurred in ...This study investigates the cloud macro-and micro-physical characteristics in the convective and stratiform regions and their different responses to the seeding for mixed convective-stratiform clouds that occurred in Shandong province on 21 May 2018,based on the observations from the aircraft,the Suomi National Polar-Orbiting Partnership(NPP)satellite,and the high-resolution Himawari-8(H8)satellite.The aircraft observations show that convection was deeper and radar echoes were significantly enhanced with higher tops in response to seeding in the convective region.This is linked with the conversion of supercooled liquid droplets to ice crystals with released latent heat,resulting in strengthened updrafts,enhanced radar echoes,higher cloud tops,and more and larger precipitation particles.In contrast,in the stratiform cloud region,after the Silver Iodide(AgI)seeding,the radar echoes become significantly weaker at heights close to the seeding layer,with the echo tops lowered by 1.4–1.7 km.In addition,a hollow structure appears at the height of 6.2–7.8 km with a depth of about 1.6 km and a diameter of about 5.5 km,and features such as icing seeding tracks appear.These suggest that the transformation between droplets and ice particles was accelerated by the seeding in the stratiform part.The NPP and H8 satellites also show that convective activity was stronger in the convective region after seeding;while in the stratiform region,a cloud seeding track with a width of 1–3 km appears 10 km downstream of the seeding layer 15 minutes after the AgI seeding,which moves along the wind direction as width increases.展开更多
Using data of airborne particle measurement system, weather radar and Ka-band millimeter wave cloud-meter, physical structure characteristics of a typical stable stratiform cloud in Hebei Province on February 27, 2018...Using data of airborne particle measurement system, weather radar and Ka-band millimeter wave cloud-meter, physical structure characteristics of a typical stable stratiform cloud in Hebei Province on February 27, 2018 was analyzed. Research results showed that the detected cloud system was the precipitation stratiform cloud in the later stage of development. The cloud layer developed stably, and the vertical structure was unevenly distributed. The concentration of small cloud particles in high-level clouds was low, and it fluctuated greatly in space, and presented a discontinuous distribution state. The concentration of large cloud particles and precipitation particles was high, which was conducive to the growth of cloud droplets and the aggregation of ice crystals. The concentration of small cloud particles and the content of supercooled water were high in the middle and low-level clouds. The precipitation cloud system had a significant hierarchical structure, which conformed to the "catalysis-supply" mechanism. From the upper layer to the lower layer, the cloud particle spectrum was mainly in the form of single peak or double peak distribution, which showed a monotonic decreasing trend in general. The spectral distribution of small cloud particles in the cloud was discontinuous, and the high-value areas of spectral concentration of large cloud particles and precipitation particles were concentrated in the upper part of the cloud layer, and the particle spectrum was significantly widened. There was inversion zone at the bottom of the cloud layer, which was conducive to the continuous increase of particle concentration and the formation of large supercooled water droplets.展开更多
To analyze the effects of gas cannons on clouds and precipitation,multisource observational data,including those from National Centers for Environmental Prediction(NCEP)reanalysis,Hangzhou and Huzhou new-generation we...To analyze the effects of gas cannons on clouds and precipitation,multisource observational data,including those from National Centers for Environmental Prediction(NCEP)reanalysis,Hangzhou and Huzhou new-generation weather radars,laser disdrometer,ground-based automatic weather station,wind profiler radar,and Lin'an C-band dualpolarization radar,were adopted in this study.Based on the variational dual-Doppler wind retrieval method and the polarimetric variables obtained by the dual-polarization radar,we analyzed the microphysical processes and the variations in the macro-and microphysical quantities in clouds from the perspective of the synoptic background before precipitation enhancement,the polarization echo characteristics before,during and after enhancement,and the evolution of the fine three-dimensional kinematic structure and the microphysical structure.The results show that the precipitation enhancement operation promoted the development of radar echoes and prolonged their duration,and both the horizontal and vertical wind speeds increased.The dual-polarization radar echo showed that the diameter of the precipitation particles increased,and the concentration of raindrops increased after precipitation enhancement.The raindrops were lifted to a height corresponding to 0 to-20℃due to vertical updrafts.Based on the disdrometer data during precipitation enhancement,the concentration of small raindrops(lgN_(w))showed a significant increase,and the mass-weighted diameter D_(m)value decreased,indicating that the precipitation enhancement operation played a certain“lubricating”effect.After the precipitation enhancement,the concentration of raindrops did not change much compared with that during the enhancement process,while the Dm increased,corresponding to an increase in rain intensity.The results suggest the positive effect of gas cannons on precipitation enhancement.展开更多
本文使用风廓线雷达、跑道自动观测及多普勒天气雷达等观测资料,对2020年5月14日半干旱地区兰州的一次弱天气尺度强迫下的干下击暴流(简称“5.14”)过程的发生和演变特征进行了分析;应用中尺度数值模式WRF(Weather Research and Forecas...本文使用风廓线雷达、跑道自动观测及多普勒天气雷达等观测资料,对2020年5月14日半干旱地区兰州的一次弱天气尺度强迫下的干下击暴流(简称“5.14”)过程的发生和演变特征进行了分析;应用中尺度数值模式WRF(Weather Research and Forecasting)对该次过程的形成、移动及辐散出流区上空的水凝物演变特征进行了模拟,探讨了“5.14”过程外流传播的可能机制。结果表明:“5.14”过程的生命期约为30 min,云顶高度在9 km以上。在云体移向后侧3~6 km高度,同时出现突发性干冷空气急流侵入,云体断裂,云顶崩塌,动量下传和中低空1~4 km高度辐散出流急流,是下击暴流外流发生的可能原因。雪晶碰撞过冷云滴使之冻结合并,形成了下沉及外流区域的云中霰粒子均快速增长,模拟的霰粒子混合比在下击暴流暴发时增大了105倍;下沉区霰粒子加速了云中冷池的形成,是激发强下沉气流的原因之一。随着云体的移动,强下沉气流在地面上产生辐散出流,和相邻的辐散出流间交汇引起气流间的辐合上升运动,在云体移动方向前沿的下沉气流两侧形成两个气流上升区;随着干冷入流急流的深入,在云体移动方向激发出两个垂直环流,垂直环流由一支云内上升气流与一支紧邻的湿下沉气流相伴而成。垂直环流中的湿下沉气流在近地面形成冷池扩散促使了下击暴流的暴发,激发阵风锋。阵风锋向下击暴流辐散中心的外流方向扩散,阵风锋前的暖湿上升气流有利于新生单体合并进原风暴,风暴发展加强,随着阵风锋推进切断了暖湿上升气流导致重冷云顶下沉,云顶的不断上冲和崩溃形成了下击暴流的外流传播过程。阵风锋前的上升气流输送的雨滴粒子在0°C温度层附近冻结,冻结过程中释放的热量导致外流传播过程中0°C温度层不断升高,云中下沉的霰粒子融化层升高,融化后形成的雨滴粒子在下落过程中的蒸发层增大,霰粒子融化吸热及雨水在下降过程中蒸发吸热使得近地面冷池不断增强导致地面风速在辐散传播过程中加大,是下击暴流外流传播中地面大风形成的重要原因。另一方面,上升气流通过凝结作用加热大气加强上升运动。下沉气流的发展有助于形成和维持对流特征环流及冷池。下击暴流形成后,在云体移动方向上不断形成的垂直闭合环流是下击暴流辐散中心的移动机制,由于地面冷池外流的辐合抬升作用,移动方向的上升气流区范围不断增大,垂直闭合环流受到上升气流区阻挡无法新生,同时由于云体东移,维持下击暴流垂直闭合环流结构中水凝物的循环减弱使垂直闭合环流结构消散,导致下击暴流辐散中心减弱消亡。与以往研究相比较,本次干下击暴流发生时也出现了云体后侧入流急流、雷达回波反射率因子核下降、动量下传、霰粒子含水量大及水凝物融化蒸发过程吸热形成冷池等特征,但此次干下击暴流辐散中心有明显的垂直闭合环流,是下击暴流辐散中心的启动和维持机制,同时下击暴流辐散中心与阵风锋的形成密切相关,而阵风锋过程是造成此次干下击暴流的外流传播形成地面大风的主要原因。展开更多
本文利用"太行山东麓人工增雨防雹作业技术试验"的飞机和地面雷达观测数据,重点研究分析了2018年5月21日一次典型西风槽天气系统影响下的层状云微物理特征。结果表明,-5℃层的过冷水含量低于0.05 g m^-3,冰粒子数浓度量级10^1...本文利用"太行山东麓人工增雨防雹作业技术试验"的飞机和地面雷达观测数据,重点研究分析了2018年5月21日一次典型西风槽天气系统影响下的层状云微物理特征。结果表明,-5℃层的过冷水含量低于0.05 g m^-3,冰粒子数浓度量级10^1~10^2 L^-1。冰粒子数浓度高值区主要以针状和柱状冰晶为主。这可能低层是Hallett-Mossop机制和其他冰晶繁生机制共同作用下所产生的冰晶碎片在冰面过饱和条件下凝华增长所形成的。冰粒子数浓度低值区的冰晶形状基本以片状或枝状为主。-5℃层的冰雪晶增长主要以凝华和聚并增长为主,凇附过程很弱。零度层附近云水含量峰值区的液态水占比达到70%以上。云水含量峰值区的粒子主要以直径10~50μm的云滴为主,伴随着少量聚合状冰晶。零度层其他区域的过冷水含量维持在0.05 g m^-3左右,冰晶形态主要以聚合状、凇附状及霰粒子为主。液水层则主要以球形液滴及半融化状态的冰粒子为主。垂直探测表明:零度层以上的冰雪晶数浓度呈现随高度递增的趋势。在发展稳定的层状云内,混合层的过冷水含量很低,冰粒子主要通过凝华和聚并过程增长,云体冰晶化程度较高。而在发展较为旺盛的层状云区里过冷水含量也较高,大量液滴的存在也表明混合层冰-液相之间的转化不充分。不同温度层的粒子谱显示,冷水含量高值区的冰粒子平均浓度比过冷水低值区高,但平均直径比过冷水低值区小。展开更多
基金supported by the National Key Research and Development Project(Grant No.2019YFA0606803,2016YFA0601704)the National Natural Science Foundation of China(Grant No.41925022)+1 种基金the Innovation and Development Project of China Meteorological Administration(CXFZ2022J036)the Science and Technology Development Fund of Hubei Meteorological Bureau(Grant No.2017Y06,2017Y07,2016Y06,2019Y10).
文摘This study investigates the cloud macro-and micro-physical characteristics in the convective and stratiform regions and their different responses to the seeding for mixed convective-stratiform clouds that occurred in Shandong province on 21 May 2018,based on the observations from the aircraft,the Suomi National Polar-Orbiting Partnership(NPP)satellite,and the high-resolution Himawari-8(H8)satellite.The aircraft observations show that convection was deeper and radar echoes were significantly enhanced with higher tops in response to seeding in the convective region.This is linked with the conversion of supercooled liquid droplets to ice crystals with released latent heat,resulting in strengthened updrafts,enhanced radar echoes,higher cloud tops,and more and larger precipitation particles.In contrast,in the stratiform cloud region,after the Silver Iodide(AgI)seeding,the radar echoes become significantly weaker at heights close to the seeding layer,with the echo tops lowered by 1.4–1.7 km.In addition,a hollow structure appears at the height of 6.2–7.8 km with a depth of about 1.6 km and a diameter of about 5.5 km,and features such as icing seeding tracks appear.These suggest that the transformation between droplets and ice particles was accelerated by the seeding in the stratiform part.The NPP and H8 satellites also show that convective activity was stronger in the convective region after seeding;while in the stratiform region,a cloud seeding track with a width of 1–3 km appears 10 km downstream of the seeding layer 15 minutes after the AgI seeding,which moves along the wind direction as width increases.
基金Supported by National Key R&D Plan Projects (2018YFC1507900)Hebei Province Science and Technology Plan Program(20375402D)。
文摘Using data of airborne particle measurement system, weather radar and Ka-band millimeter wave cloud-meter, physical structure characteristics of a typical stable stratiform cloud in Hebei Province on February 27, 2018 was analyzed. Research results showed that the detected cloud system was the precipitation stratiform cloud in the later stage of development. The cloud layer developed stably, and the vertical structure was unevenly distributed. The concentration of small cloud particles in high-level clouds was low, and it fluctuated greatly in space, and presented a discontinuous distribution state. The concentration of large cloud particles and precipitation particles was high, which was conducive to the growth of cloud droplets and the aggregation of ice crystals. The concentration of small cloud particles and the content of supercooled water were high in the middle and low-level clouds. The precipitation cloud system had a significant hierarchical structure, which conformed to the "catalysis-supply" mechanism. From the upper layer to the lower layer, the cloud particle spectrum was mainly in the form of single peak or double peak distribution, which showed a monotonic decreasing trend in general. The spectral distribution of small cloud particles in the cloud was discontinuous, and the high-value areas of spectral concentration of large cloud particles and precipitation particles were concentrated in the upper part of the cloud layer, and the particle spectrum was significantly widened. There was inversion zone at the bottom of the cloud layer, which was conducive to the continuous increase of particle concentration and the formation of large supercooled water droplets.
基金National Natural Science Foundation of China(41675029)Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX18_0998)+1 种基金Science and Technology Program of Huzhou(2021GZ14,2020GZ31)Science and Technology(Key)Program of Zhejiang Meteorological Service(2021ZD27)。
文摘To analyze the effects of gas cannons on clouds and precipitation,multisource observational data,including those from National Centers for Environmental Prediction(NCEP)reanalysis,Hangzhou and Huzhou new-generation weather radars,laser disdrometer,ground-based automatic weather station,wind profiler radar,and Lin'an C-band dualpolarization radar,were adopted in this study.Based on the variational dual-Doppler wind retrieval method and the polarimetric variables obtained by the dual-polarization radar,we analyzed the microphysical processes and the variations in the macro-and microphysical quantities in clouds from the perspective of the synoptic background before precipitation enhancement,the polarization echo characteristics before,during and after enhancement,and the evolution of the fine three-dimensional kinematic structure and the microphysical structure.The results show that the precipitation enhancement operation promoted the development of radar echoes and prolonged their duration,and both the horizontal and vertical wind speeds increased.The dual-polarization radar echo showed that the diameter of the precipitation particles increased,and the concentration of raindrops increased after precipitation enhancement.The raindrops were lifted to a height corresponding to 0 to-20℃due to vertical updrafts.Based on the disdrometer data during precipitation enhancement,the concentration of small raindrops(lgN_(w))showed a significant increase,and the mass-weighted diameter D_(m)value decreased,indicating that the precipitation enhancement operation played a certain“lubricating”effect.After the precipitation enhancement,the concentration of raindrops did not change much compared with that during the enhancement process,while the Dm increased,corresponding to an increase in rain intensity.The results suggest the positive effect of gas cannons on precipitation enhancement.
文摘本文使用风廓线雷达、跑道自动观测及多普勒天气雷达等观测资料,对2020年5月14日半干旱地区兰州的一次弱天气尺度强迫下的干下击暴流(简称“5.14”)过程的发生和演变特征进行了分析;应用中尺度数值模式WRF(Weather Research and Forecasting)对该次过程的形成、移动及辐散出流区上空的水凝物演变特征进行了模拟,探讨了“5.14”过程外流传播的可能机制。结果表明:“5.14”过程的生命期约为30 min,云顶高度在9 km以上。在云体移向后侧3~6 km高度,同时出现突发性干冷空气急流侵入,云体断裂,云顶崩塌,动量下传和中低空1~4 km高度辐散出流急流,是下击暴流外流发生的可能原因。雪晶碰撞过冷云滴使之冻结合并,形成了下沉及外流区域的云中霰粒子均快速增长,模拟的霰粒子混合比在下击暴流暴发时增大了105倍;下沉区霰粒子加速了云中冷池的形成,是激发强下沉气流的原因之一。随着云体的移动,强下沉气流在地面上产生辐散出流,和相邻的辐散出流间交汇引起气流间的辐合上升运动,在云体移动方向前沿的下沉气流两侧形成两个气流上升区;随着干冷入流急流的深入,在云体移动方向激发出两个垂直环流,垂直环流由一支云内上升气流与一支紧邻的湿下沉气流相伴而成。垂直环流中的湿下沉气流在近地面形成冷池扩散促使了下击暴流的暴发,激发阵风锋。阵风锋向下击暴流辐散中心的外流方向扩散,阵风锋前的暖湿上升气流有利于新生单体合并进原风暴,风暴发展加强,随着阵风锋推进切断了暖湿上升气流导致重冷云顶下沉,云顶的不断上冲和崩溃形成了下击暴流的外流传播过程。阵风锋前的上升气流输送的雨滴粒子在0°C温度层附近冻结,冻结过程中释放的热量导致外流传播过程中0°C温度层不断升高,云中下沉的霰粒子融化层升高,融化后形成的雨滴粒子在下落过程中的蒸发层增大,霰粒子融化吸热及雨水在下降过程中蒸发吸热使得近地面冷池不断增强导致地面风速在辐散传播过程中加大,是下击暴流外流传播中地面大风形成的重要原因。另一方面,上升气流通过凝结作用加热大气加强上升运动。下沉气流的发展有助于形成和维持对流特征环流及冷池。下击暴流形成后,在云体移动方向上不断形成的垂直闭合环流是下击暴流辐散中心的移动机制,由于地面冷池外流的辐合抬升作用,移动方向的上升气流区范围不断增大,垂直闭合环流受到上升气流区阻挡无法新生,同时由于云体东移,维持下击暴流垂直闭合环流结构中水凝物的循环减弱使垂直闭合环流结构消散,导致下击暴流辐散中心减弱消亡。与以往研究相比较,本次干下击暴流发生时也出现了云体后侧入流急流、雷达回波反射率因子核下降、动量下传、霰粒子含水量大及水凝物融化蒸发过程吸热形成冷池等特征,但此次干下击暴流辐散中心有明显的垂直闭合环流,是下击暴流辐散中心的启动和维持机制,同时下击暴流辐散中心与阵风锋的形成密切相关,而阵风锋过程是造成此次干下击暴流的外流传播形成地面大风的主要原因。
文摘本文利用"太行山东麓人工增雨防雹作业技术试验"的飞机和地面雷达观测数据,重点研究分析了2018年5月21日一次典型西风槽天气系统影响下的层状云微物理特征。结果表明,-5℃层的过冷水含量低于0.05 g m^-3,冰粒子数浓度量级10^1~10^2 L^-1。冰粒子数浓度高值区主要以针状和柱状冰晶为主。这可能低层是Hallett-Mossop机制和其他冰晶繁生机制共同作用下所产生的冰晶碎片在冰面过饱和条件下凝华增长所形成的。冰粒子数浓度低值区的冰晶形状基本以片状或枝状为主。-5℃层的冰雪晶增长主要以凝华和聚并增长为主,凇附过程很弱。零度层附近云水含量峰值区的液态水占比达到70%以上。云水含量峰值区的粒子主要以直径10~50μm的云滴为主,伴随着少量聚合状冰晶。零度层其他区域的过冷水含量维持在0.05 g m^-3左右,冰晶形态主要以聚合状、凇附状及霰粒子为主。液水层则主要以球形液滴及半融化状态的冰粒子为主。垂直探测表明:零度层以上的冰雪晶数浓度呈现随高度递增的趋势。在发展稳定的层状云内,混合层的过冷水含量很低,冰粒子主要通过凝华和聚并过程增长,云体冰晶化程度较高。而在发展较为旺盛的层状云区里过冷水含量也较高,大量液滴的存在也表明混合层冰-液相之间的转化不充分。不同温度层的粒子谱显示,冷水含量高值区的冰粒子平均浓度比过冷水低值区高,但平均直径比过冷水低值区小。
