冷空气侵入台风“珍珠”的多普勒雷达回波特征

利用汕头和厦门的多普勒雷达资料、NCEP再分析等资料,研究2006年5月17日台风“珍珠”的短时特大暴雨特征。多普勒雷达探测表明,17日18～19 h,在台风“珍珠”的核半径附近,正、负径向速度极值区分布不对称,即台风前进方向左侧的径向速度明显地大于右侧,研究表明这种特殊情况是由于冷空气(东北风)侵入所导致的,而且该冷空气侵入主要位于4 km以下的中低层,正是因为冷空气侵入造成强迫抬升,加剧不稳定能量释放,触发强降水产生,冷空气影响后期导致台风迅速减弱。与雷达速度场回波观测到的冷空气侵入相对应,17日18 h NCEP风速资料显示在中低层(约1～3 km)台风中心偏西侧,存在明显的全风速高值区,而除了受冷空气影响部位外,台风前进方向的右侧各层风速仍然大于左侧。利用蓝金模式模拟结果,可进一步证实了在台风前进方向左侧的中低层,东北向气流侵入台风涡旋的事实。通过计算物理量表明,在冷空气侵入区域存在高θse密集锋区,θse密集带从底层向高层、由偏东向偏西、由偏南向偏北方向倾斜,闽南地区的特大暴雨就发生在高θse的密集锋区附近。     

Development of an Automatic Echo-counting Program for HROFFT Spectrograms

Radio meteor observations by Ham-band beacon or FM radio broadcasts using “Ham-band Radio meteor Observation Fast Fourier Transform” (HROFFT) an automatic operating software have been performed widely in recent days. Previously, counting of meteor echoes on the spectrograms of radio meteor observation was performed manually by observers. In the present paper, we introduce an automatic meteor echo counting software application. Although output images of the HROFFT contain both the features of meteor echoes and those of various types of noises, a newly developed image processing technique has been applied, resulting in software that enables a useful auto-counting tool. There exists a slight error in the processing on spectrograms when the observation site is affected by many disturbing noises. Nevertheless, comparison between software and manual counting revealed an agreement of almost 90%. Therefore, we can easily obtain a dataset of detection time, duration time, signal strength, and Doppler shift of each meteor echo from the HROFFT spectrograms. Using this software, statistical analyses of meteor activities is based on the results obtained at many Ham-band Radio meteor Observation (HRO) sites throughout the world, resulting in a very useful “standard” for monitoring meteor stream activities in real time.     

GPS-RTK与数字测深仪在近海工程中的应用

介绍了GPS-RTK配合数字测深仪进行水下地形测量的原理、工作方法和注意事项。利用GPS-RTK和数字测深仪联合作业系统在大连近海工程中对堪察孔位的3维信息进行测量,在实际应用中取得了良好效果,不仅提高了工作效率,而且保证了精度。     

一次局地突发短时冰雹过程雷达回波分析

本文利用佳木斯雷达站的观测资料,对2010年8月12日清晨桦南县出现的局地突发短时冰雹云的初生、发展、成熟和消亡各阶段的回波演变进行了分析.重点讨论了这次过程中产生冰雹的对流单体回波特征,结合大尺度天气背景及相关雷达产品分析,揭示了此次局地突发短时冰雹天气发生的主要原因,并得出了对突发性冰雹天气的临近预报有参考意义的结...     

闽西北地区降水回波特征和人工增雨作业条件分析

利用新一代天气雷达回波资料、850 hPa天气图和地面降水资料对闽西北地区的云雨资源、有利人工增雨作业的天气系统、降水回波特征及人工增雨作业指标进行分析.结果表明:福建闽西北地区有利于开展人工增雨作业的主要天气系统可分为9类:大陆高压、副高外围、暖区辐合、热带辐合带、低槽、台风(低压)、低涡、低涡切变和其他类.积层混合...     

新一代天气雷达与TWR01小天气雷达在一次强降水天气过程中的对比分析

通过对贵阳多普勒雷达和独山TWR01小天气雷达资料在一次强降水天气过程中四个时段的观测资料和四个时段的自记降水资料进行分析对比．得出新一代多普勒天气雷达由于贵州地形影响等原因．存在一定的探测盲区,而TWR01小雷达对小范围的对流云层观测更清楚、更接近当时天空的实际情况,是多普勒天气雷达很好的补充。     

核磁共振T2谱反演影响因素

为了进一步改进完善核磁共振T2谱反演算法,利用核磁共振正演模拟信号,研究回波间隔、原始回波采集数量、信噪比等因素对反演结果的影响,同时在不同信噪比下对最优化T2谱反演算法、奇异值分解反演算法进行比较分析。研究表明:采集弛豫信号时,回波间隔大小的设置与回波数量、组分大小相匹配,才能得到最佳的反演效果;信噪比越高反演效果越好,当信噪比大于25时反演谱与构造谱基本吻合;在反演不同信噪比理论回波数据时,最优化反演方法对信噪比要求不高,奇异值分解反演方法对信噪比要求高,而奇异值分解反演速度较快。     

Simrad EM多波束声纳系统回波强度数据的分析与应用

首先分析了Simrad EM多渡束声纳系统回渡强度数据获取时系统进行的增益处理,分别探讨了深度数据包和海底图像数据包中回波强度数据的表征内容及意义,研究了不同数据包中回波强度数据的记录方式、特点及应用范围,为多波束水下目标识别和海底底质分类研究提供准确、表述清晰的基础数据.     

CHARACTERISTICS AND RELATIONS OF LIGHTNING AND RADAR ECHOES FOR STRONG CONVECTIVE RAINSTORMS IN YUNNAN

Based on cloud-ground lightning data and Doppler weather radar echo products, both thecharacteristics and the relations of lightning and radar echoes for strong convective rainstorms over Yunnanare analyzed during the flood season of 2007. The results show that most rainstorms are convective in whichlightning is mostly negative and the negative lightning number accounts for more than 90% of the total.Although the correlation between precipitation and the lightning number is small on the rainstorm day, thelarge day-lightning frequency usually produces heavy precipitation. Hourly evolution of precipitation andlightning frequency shows peak-style characteristics. And their evolution is very coherent in strongrainstorm, but lightning often occurs before precipitation, whose peaks are in phase with or 1-to-2-hourlagged behind that of lightning frequency. Meanwhile the peaks of positive frequency are in phase with orfall behind that of precipitation. When the wind field is heterogeneous in radial velocity, it is conducive toboth the development of convection echoes and occurrence of lightning. Strong lightning-producingconvective rainstorms correspond to strong echo fields and usually result in reflectivity above 30 dBZ andecho top ET of more than 9 km, respectively.     

铜仁市一次雷暴大风过程分析

利用常规站资料、ERA5资料（0.25°×0.25°）以及务川雷达和铜仁新一代多普勒天气雷达资料对2022年4月24日发生在贵州铜仁市多个区（县）的一次雷暴大风过程进行分析,结果表明：（1）此次天气过程是发生上干下湿的不稳定环境中,高空槽、南支槽、低涡、切变线和地面辐合线都为此次强对流天气过程提供了触发条件。（2）大的DCAPE值、中层中等强度的垂直风切变和低层较强的垂直风切变以及较大的850hPa与500hPa的温差都是利于大风产生的条件。（3）大风常常出现在弓形回波前部突出处,高悬的强回波、弱回波区、高的回波顶高以及径向速度中出现逆风区和强并且深厚的中层径向辐合等都是出现大风天气的雷达产品特征。