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121.
火箭增雨效果雷达回波分析 总被引:4,自引:1,他引:3
利用2004年6月12日甘肃省永登县雷达观测对流云的加密资料,选取了2次相似对流云过程分别作为目标云和对比云,探讨了目标云作业前后较对比云雷达回波有关参数的显著变化,并结合地面雨量点观测资料对地面人工增雨作业效果进行了初步分析,结果表明:目标云在降水、生命期特征、回波垂直特征参数变化方面,表现出作业前后较对比云存在明显差异,目标云作业40 m in后地面产生0.6 mm降水,而对比云则从新生发展到减弱消散阶段经历较短的时间(30 m in),地面并无降水产生,从而推断本次人工增雨达到了一定的预计效果。 相似文献
122.
强降水云物理过程的三维数值模拟研究 总被引:35,自引:9,他引:26
利用改进的三维完全弹性强对流云模式,模拟了1998年7月21日晨发生在武汉附近的特大暴雨个例,结果显示,该模式模拟得到的降雨量与实测接近,计算得到的雷达回波强度最大值也与实际观测相一致,说明该模式对实际对流性强降水具有较好的模拟能力.在此基础上,通过冷云和暖云两种不同情况的比较分析,研究了云微物理过程在强降水形成过程中的作用.模拟结果表明,详细云物理过程的考虑对深入理解武汉这次强降水的形成过程是有意义的.该个例雨水的形成主要是暖雨过程,冰相微物理过程对该对流性强降水过程的发展和演变有重要的促进作用.在形成雨水的冷相过程中,霰的融化及其在0 ℃层下碰并云水形成雨水的过程是主要的.模式云在0 ℃层附近存在明显的雷达回波亮带,亮带中间含有强回波核和及地下挂回波.分析表明,这种强回波核和下挂回波的产生主要是由于冰相粒子在0 ℃层融化形成的,融化的冰相粒子与云滴碰并又加速雨水的产生.在这些融化的冰相粒子中,贡献最大的是霰粒.文中还分析了该强降水暴雨云维持长时间强降水的云物理机制.在低层大气温暖高湿和环境风切变有利条件下,倾斜上升气流和下沉气流之间的准稳态结构可能是暴雨强降水得以长时间维持的重要原因. 相似文献
123.
通过分析我国南北地震带(以下简称南北带)有仪器记录以来发生的大震后,发现存在约10年主体大震活动区,并自北而南有4次转移图像;同时对汶川8级大震前后的震情活动进行分析,认为未来10年南北带北段及以西地区将进入活跃期,很有可能发生多次7级以上地震,但也可能南移;未来几年四川地区可能再次发生大震,甘肃东南部地区有可能发生6级以上地震。 相似文献
124.
南海中西部地貌单元划分及其特征和成因分析 总被引:1,自引:0,他引:1
南海中西部处于南海北部和南部的过渡带,夹持于印支地块和南海海底扩张中心之间,其特殊的地貌对于研究整个南海地质地貌有重要意义。本文基于广州海洋地质调查局在南海中西部海洋地质调查项目获取的水深、底质调查及地震剖面数据,结合该海域以往研究成果,提取了有关地貌的信息,编制了南海中西部地貌图。把研究区划分出陆架、陆坡和深海盆地三个二级地貌单元,以及水下岸坡、水下浅滩、海岭、峡谷、麻坑、阶地、盆地、海台、海山、深海扇、深海平原等众多次级地貌单元。文章详细描述了该海域各地貌单元的特征,提出了断层、火山、构造隆起和浊流等地质作用是本区地貌形成的主要因素。 相似文献
125.
By using the conventional observations, radar data, NCEP/NCAR FNL 1o×1o reanalysis data and numerical simulation data and with the construction and calculation of radar echo parameters, this paper presents the structural characteristics and physical processes of a short-time heavy precipitation supercell that occurred in the squall line process in Shanxi Province on 24 June 2020. The results show that this squall line event occurred in front of a surface cold front, combined with infiltration of low-level cold air and continuous increase of near-surface humidity in the afternoon. The surface mesoscale convergence line and mesoscale dew point front contributed to the development and systemization of the squall line by a large degree. The short-time extremely heavy precipitation in Pingshun County was caused by the development of a supercell from thunderstorm cells on the front side of the squall line. The characteristics of sharp increase in vertical integral liquid water content, persistent increase in reflectivity factor and continuous rise in the echo top height appeared about 23 min earlier than the severe precipitation, which has qualitative indicating significance for the nowcasting of short-time heavy precipitation. A quantitative analysis of the radar echo parameters suggests that the “sudden drop”of FV40 was a precursor signal of cells’coalescence and rapid development to the mature stage. The areal change of the echo core at the 6 km height was highly subject to the merging and developing of cells, the rapid change of hydrometeor particles in clouds and the precipitation intensity. Changes in the cross-sectional area of convective cells at different heights can indirectly reflect the changes of liquid particles and ice particles in clouds, which is indicatively meaningful for predicting the coalescing and developing-to-maturing of cells and heavy precipitation 30-45 min earlier. A comprehensive echo parameter prediction model constructed by the random forest principle can predict the magnitude of short-time heavy precipitation 40-50 min in advance. Numerical simulation reveals that large amounts of water vapor existed in the near-surface atmosphere, and that the cells rapidly obtained moisture from the ambient atmosphere and developed rapidly through maternal feeding. The cold cloud zone was narrow, upright and had a high stretch height. The upward motion in clouds was strong and deep, and very rich in liquid water content. The graupel particles had a large vertical distribution range, the coexistence area of graupel and snow was large, the height of raindrops was close to the surface with a wide horizontal scale, and the precipitation efficiency was high. These may be the important elements responsible for the occurrence of the short-time heavy precipitation that exceeded historical extreme values. On the basis of the above analyses, a comprehensive parameter (CP) prediction model is worked out, which can estimate the developing trend of supercells and the intensity of short-time heavy precipitation about 1 h in advance. 相似文献
126.
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 dual polarization 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 (lgNw) showed a significant increase, and the mass-weighted diameter Dm 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. 相似文献
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一次雷暴前后大气折射率的多普勒天气雷达测量试验及结果 总被引:3,自引:1,他引:2
由温度、气压和水汽压决定的大气折射率会影响天气雷达电磁波的传播路径和目标回波的相位。因此,通过测量目标回波相位的变化能够算出大气折射率的变化,进而得到水汽信息,为研究局地对流天气和水汽平流提供资料。本文阐述了多普勒天气雷达反演大气折射率的原理和方法,并利用江苏省气象台的S波段多普勒天气雷达反演了一次雷暴过程前后的大气折射率,表明了雷达探测大气折射率的可靠性。这项工作有望为研究水汽变化和天气过程提供高分辨率的遥感资料,也可以为数值模式提供水汽场辅助数据,有良好的应用前景。 相似文献