雷达定量降水估算在水文模式汛期洪水预报中的应用试验

通过雷达测雨技术获得高时空分辨率的降雨信息,作为水文模型的输入,用以提高水文预报的精度。文章以湖北省白莲河流域为例,利用分组Z-I关系转化雷达反射率为雨强,运用地面雨量站网实测雨量对其进行校准,将不同方法估算得到的雨量结果输入新安江模型进行洪水预报测试,结果表明未校准雷达估算降雨量直接输入水文模型,其结果是不理想的;利用校准后的雷达估算降雨量进行洪水预报,精度得到了很大提高。     

Study on a Mesoscale Convective Vortex Causing Heavy Rainfall during the Mei-yu Season in 2003

The strong heavy rainfall on 3-5 July 2003 causing the severe flooding in Huaihe River basin (HRB), China is studied. It is noted that there are sometimes mesoscale convective vortex (MCV) in East Asia during the mei-yu season. Simulation results from the ARPS (Advanced Regional Prediction) data analysis system (ADAS) and WRF model were used to study the development of the mesoscale convective system (MCS) and mesoscale convective vortex (MCV). It is confirmed that the MCV formed during the development of a...     

Radar Data Assimilation for the Simulation of Mesoscale Convective Systems

A heavy rainfall case related to Mesoscale Convective Systems (MCSs) over the Korean Peninsula was selected to investigate the impact of radar data assimilation on a heavy rainfall forecast. The Weather Research and Forecasting (WRF) three-dimensional variational (3DVAR) data assimilation system with tuning of the length scale of the background error covariance and observation error parameters was used to assimilate radar radial velocity and reflectivity data. The radar data used in the assimilation experiments were preprocessed using quality-control procedures and interpolated/thinned into Cartesian coordinates by the SPRINT/CEDRIC packages. Sensitivity experiments were carried out in order to determine the optimal values of the assimilation window length and the update frequency used for the rapid update cycle and incremental analysis update experiments. The assimilation of radar data has a positive influence on the heavy rainfall forecast. Quantitative features of the heavy rainfall case, such as the maximum rainfall amount and Root Mean Squared Differences (RMSDs) of zonal/meridional wind components, were improved by tuning of the length scale and observation error parameters. Qualitative features of the case, such as the maximum rainfall position and time series of hourly rainfall, were enhanced by an incremental analysis update technique. The positive effects of the radar data assimilation and the tuning of the length scale and observation error parameters were clearly shown by the 3DVAR increment.     

新一代天气雷达与闪电定位仪资料在一次区域性暴雨过程中的分析应用

根据一次大范围暴雨天气过程的闪电定位资料和多普勒雷达资料,利用统计和对比分析的方法,发现了闪电发生频数、强度和雷达回波强度在时间序列上有较好的一致性;在雷达回波发展的不同阶段,闪电发生的位置与雷达强回波位置有时相同,有时偏离,有时甚至无闪电发生;雷达回波速度场分析表明,在低层存在不利于对流发展的环境风场特征时,降水回波在向测站移动的过程中趋于消散,闪电频数也随着减少;在降水回波速度辐合区,对应闪电活动频繁。     

Analysis of the Initial Stage Intracloud Lightning Using the Pulse Location Technique Based on the Fast Electric Field Change

Academy of Sciences,Beijing 100029 2 Lanzhou University,Lanzhou 730000 3 Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences,Lanzhou 730000 4 Nanjing University of Information Science＆Technology,Nanjing 210044
Using both fast and slow electric field change sensors and field mill,multi-station observations on lightning flashes over China inland plateau areas were conducted during the summer of 2004.All of the stations were synchronized by GPS with a time-resolution of±50 ns.Using the different time of arrival（DTOA）and based on the fast electric field change sensor,a lightning radiation location technique was developed.Radiation pulses in the initial stages of five intracloud（IC）lightning discharges which occurred on 20 August were analyzed.The results indicate that the technique developed could effectively locate the lightning radiation sources.Furthermore,the lightning discharges were compared with the Doppler radar data.The results show that the radiation sources were well associated with the storm development.When the storm was at the mature stage with an echo top of about 10.9 km,the radiation sources ranged from 5.2 to 8.3 km above mean sea level;when the storm gradually became weaker,with echo top of about 7.9 km,the radiation sources ranged from 3.0 to 5.9 km.In particular,one of the IC lightning discharges ranged from 3.0 to 4.9 km during the dissipation stage of the storm.The results also indicate that the radiation sources were closely associated with the high reflectivity region（25–50 dBZ）of the storm,which,to some extent,demonstrates the reliability of the location results,thereby showing that multi-station observations of fast electric field change sensors could be a useful tool for monitoring the storm development.Location errors from radiation sources were also compared with the radar data and the results of a simple simulation.It was found that the errors were getting smaller when the radiation sources approached the center of the detection network, and vice versa.Compared with the limited experimental observations,the simulation results were found capable of effectively reflecting the location errors.     

BP神经网络在多普勒雷达降水量的估测中的应用

利用2005年4次降雨过程的多普勒雷达体扫的回波强度资料及相应的雨量计观测资料, 通过BP神经网络方法来估测临沂地区的降雨量, 同时以改进的最佳窗概率配对法建立的Z-R关系估测的降雨量为对照, 进一步验证BP神经网络方法的优越性。根据各个站点的平均相对误差、 均方根差、 相关系数和相关曲线斜率4个指标的比较, 小时雨量和累计降雨量估测结果表明： BP神经网络估测精度要明显优于Z-R关系式, 训练样本的精度高于检验样本的精度, BP神经网络估测的降雨量与站点实测雨量吻合性较好, 能够较真实地反映地面降雨情况; Z-R关系式估测的降雨量随着雨强的不同表现为不同程度的低估现象。     

利用单多普勒雷达资料做冷流暴雪的中尺度分析

基于单多普勒天气雷达资料采用EVAP方法反演风场, 并结合径向速度、 反射率因子、 自动气象站和探空风场等观测资料, 对2005年12月6～7日山东半岛一次冷流暴雪过程的中尺度特征进行了深入分析, 结果表明： (1)雷达回波呈狭窄带状, 移动缓慢近乎停滞, 径向速度上存在风向切变线, 烟台和威海的暴雪不同步是冷流暴雪的典型特征; (2)首次通过雷达反演证实了逆风区实际就是风场切变在径向速度图上的反映, 垂直各层水平风场存在中尺度切变线, 且与强回波带相对应, 切变线的位置决定暴雪的落区; (3)通过雷达反演风场和风廓线共同揭示出强降雪产生时对流层中层有西北风、 西南风和东北风三股气流, 明显的西南气流位于850～700 hPa, 表明冷流降雪过程并非传统认为的仅有西北冷平流, 而是不同气流辐合的结果; (4)对流层中层的西南暖平流为云的播种和反馈机制提供了有利的天气背景条件, 使得冷流降雪增强, 这在常规观测资料中无法看到。     

新一代多普勒天气雷达CINRAD/CD谱宽资料分析应用初探

主要概述了多普勒天气雷达CINRAD/CD谱宽资料的物理意义、影响因素,并分析了在实际业务工作中谱宽与速度的关系.在理论分析的基础上,从气象因素、非气象因素、其它因素3个方面着重分析了影响谱宽大小的因素,并从风切变、湍流、粒子下落速度、波束宽度的横向风效应4个方面来分析谱宽与速度两者之间关系.指出风切变区除了可通过径向速度场来确定外,也可通过谱宽的大值区来确定,给出了针对不同降水类型的速度谱方差范围,以及雹云不同区域的湍能耗散率ε大小与实际降雹强度关系.另外运用谱宽数据可以对径向速度数据的可靠性进行检验,高谱宽值表明速度没有代表性.     

阳泉市强对流天气分析预报

本文通过对发生在阳泉的强对流天气的历史个例分析,得出其天气分型,结合强对流天气发生发展条件分析以及卫星云图和多普勒雷达资料的应用,得出一些强对流天气预报指标,为做好强对流天气的预报服务提供参考。     

格尔木-拉萨成品油管道沿线冻土工程和环境问题及其防治对策

格尔木拉萨成品油管线穿越青藏高原腹地多年冻土区,沿线气候严寒、冻土工程地质条件复杂.几十年来,气候变暖和人类活动已经对管道沿线的冻土环境产生了显著影响.总结了自运营以来格拉管道出现的冻土工程问题及管道沿线的生态环境问题,并就各种问题给出了相关措施和建议.同时,提出了该区管道建设和寒区环境研究的方向应包括加强管道内外检测、对管道进行风险评价、提高管道自动化管理水平、建立冻土长期监测体系以及保护沿线的生态环境等.