Analysis on Three-dimensional Structure and Echo Characteristic Quantity of a Supercell Storm

[Objective] The research aimed to study three-dimensional structure and echo characteristic quantity of a supercell storm in central Gansu on May 30,2005.[Method] By monitoring data of Lanzhou CINRAD/CC Doppler radar,the three-dimensional structure characteristics of a rare supercell storm which happened in central Gansu on May 30,2005 were analyzed.We tried to reveal three-dimensional structure and echo characteristic index of supercell storm in the northeast of Qinghai-Tibet Plateau,and find reason of rare heavy hail appearance.[Result] The large-scale strong storm was formed by the common effect of Mongolia cold vortex,low-level jet and ground cold front.When the development of main echo was mature,on reflectivity factor map,it presented obvious inverted 'V' shaped structure in left front of low-level storm,typical hooked and 'person'-type echo characteristics in the right rear.The bounded weak echo zone(vault) in low level corresponded with strong echo overhanging body in high level.It surpassed 60 dBz in the strong reflectivity factor zone.It presented one weak meso-cyclone on corresponding radial velocity map.The jumped increase characteristic of VIL could be as one of indices for judging that hail started to grow.Almost all storms(VILD ≥4.0 g/m3) had more obvious indication significance than VIL for judging heavy hail(diameter ≥20 mm).[Conclusion] The research provided reference for nowcasting of strong convection weather and artificial hail suppression.

Analysis of echo signal modulation characteristic parameters on aerial and space targets

Based on the scattering characteristic,the comparison of RCS(radar cross-section)at different positions of a target in the same direction of incidence can be obtained first by extruding or deleting part of the entity.A simulation method of aerial&space targets echo characteristics(A&STEC)is proposed that is universal to aerial and space targets.We utilize a fixed-wing UAV(unmanned aerial vehicle)and typical missiles in simulation.The echo signal modulation characteristic parameters are calculated theoretically by the atmospheric attenuation model,the finite element method and a MUMPS solver.The verification simulations show that this method can analyze the influence of the target shape,incident direction,detection position and detection frequency on echo waveform,intensity and energy distribution.The results show that the profile of echo waveform can invert the general shape of the target.The relationship between time and intensity can determine whether the target is moving towards or away from the detector in addition.These conclusions can provide a reference for the ballistic missile target tracking and the defense against UVA intrusion in theory.

A Comprehensive Observational Analysis for the Effects of Gas Cannons on Clouds and Precipitation

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.

Analysis of a Type Ⅱ Snowstorm Process in the Early Spring of 2022 in Ulanqab

Based on the observation data of meteorological stations,Doppler radar observation data of Ulanqab City,and ERA-5 reanalysis data,a snowstorm process in Ulanqab City from March 17 to 18,2022 was analyzed.The results show that this was a type Ⅱ snowstorm process generated under the joint influence of upper trough and ground low inverted trough and frontal cyclone.The main period of snowfall can be divided into two time stages,and the total snowfall was more in the south and less in the north,which was consistent with that of average specific humidity field.Water vapor conditions provided by strong water vapor transport and convergence,strong upward movement shown by large vertical velocity field,and the suction action of high-and low-layer divergence and convergence were the reasons for the hourly heavy snowfall on the 18^(th).During the process,radar echoes were mainly sheet-shaped,and composite reflectivity was 15-25 dBZ in most areas.The zero speed line in the first period was positively"S"-shaped,and there was warm advection and southwest wind.On the morning of the 18^(th),after the cold front transited the city,Ulanqab City was gradually controlled by northwest wind,and the snow tended to end.