综合识别冰雹云

通过多因子综合识别法对满城１９８６－１９８８年１０３个强对流云进行了统计分析，找出了河北满城及周围地区雷达识别冰雹去的综合指标。使用该综合指标对历史冰雹云和雷雨去资料进行拟合，对冰雹去的识别成功率达９５％。     

榆林新一代天气雷达冰雹云识别指标分析

利用2005-2007年5—9月榆林雷达站观测资料和同期的常规高空、地面观测资料及榆林市境内的冰雹灾情资料,对其中的14次冰雹天气过程分析,重点考察冰雹产生过程中冰雹云在新一代天气雷达图上的演变特征。通过对地面降雹资料和相应的雷达产品资料分析,结果表明：榆林新一代天气雷达对责任区内的冰雹预报预警具有较好的指示作用。冰雹云识别指标为：强反射率因子区（回波强度≥50dBz）在-20℃层高度附近及以上,且强回波强度越强,高度越高,愈有利于大冰雹的产生;反射率因子剖面图上出现有界弱回波区（BWER）或弱回波区（WER）,区域的大小影响降雹的持续时间和冰雹的大小;垂直累积液态水含量VIL的大值区（≥40kg／m^2）代表降冰雹的潜势,VIL值越大。降大冰雹的潜势越大。三体散射现象可作为冰雹的预报指标。     

潍坊冰雹云的雷达识别

利用潍坊１９８１－１９９０年,１９９２－１９９７年雷达回波资料和天气灾情资料,了降雹概率与回波顶高、强回波高度、回波强度的关系,用独立参数降雹条件概率法判别法冰雹云,建立了统计模式,并且利用计算机进行了实时处理,实现了智能化,具有较高的实用性     

变频单波段雷达方法识别冰雹云

为了探计用改变单波段雷达工作频率的方法识别冰雹云,对于C波段(取5.56cm波长)和S波段(取10.7cm波长)雷达,分别改变其工作频率400MHz和200MHz,计算了相应变化频率两端的那些波长情况下,三种冰雹模式(纯冰球、带水膜冰球、冰水混合球),两种冰雹谱分布型式(匀谱与指数谱)的雷达反射率因子。对于这两种波段的雷达,分别考察其长波长的雷达反射率因子与短波长的雷达反射率因子之比和冰雹直径之间的变化关系。结果表明,在一定的条件下,两种雷达都能够识别一定尺度范围的冰雹,而且以S波段雷达指数谱情况的结果最     

雷达判别宁南山区冰雹云的综合指标

本文采用多因子综合相关概率法、双参数点聚图法,综合对六盘山区151个暴雹个例进行了统计分析,找出了六盘山区雷达识别冰雹云的定量综合指标。结果表明,综合指标达到2.9时,识别雹云的成功率达92.1％。     

识别冰雹云的简易方法

正确判断云体是冰雹云还是雷雨云,这是进行人工防雹作业的重要依据。广大劳动群众在长期的防雹抗灾斗争中积累了丰富的实践经验,他们根据雹云的声、光、雷电、降水和移动等宏观特征,用耳听目测来识别雹云,并用许多生动的谚语形象地指出冰雹云的特征。例如冰雹云多“拉磨雷”、“蜂子朝王声”;“横闪多雹”;“黄云黑边子,必定下雹子”,“黑云尾,黄云头,雹子打死羊和牛”;“雹走老路”、“雹打一条线”以及雹云光象异常等等。这在人工防雹工作中起了很大的作     

应用雷达回波综合判别冰雹云

通过三种多因子综合识别法对滨州地区１９８８—１９９５年７３个强对流云进行了统计分析，找出了滨州地区雷达识别冰雹云的综合指标，并对几种综合方法进行比较     

利用雷达资料综合判别冰雹云

利用商丘1984-1991年的雷达回波资料，找出雹云与雷达回波参数之间的综合关系，统计出判别雹云的指标，分别建立了5～6月、7～9月短时预报方程。结果表明，此方法简便、实用。     

雷达识别渭北地区冰雹云技术研究

通过对陕西渭北地区各雷达站观测的回波资料和地面降雹资料分析,得出了适合识别渭北地区冰雹云的7个指标。实际应用结果表明,识别效果良好,并可以做到提前识别,为防雹作业赢得非常宝贵的时间。     

一种新型西南低涡逐步订正识别方法

西南低涡是形成于青藏高原东侧的特殊天气系统,国内学者目前对于西南低涡的识别没有统一的标准。通过分析西南低涡的主要特征,结合高度场、涡度场、风场,设计了一种适应于西南低涡的HVW识别方法,将其应用于2014年6—8月GRAPES-MESO高分辨率格点分析资料,对比与西南低涡天气图实况的差异。通过对西南低涡的识别、低涡生成和消亡时间、低涡中心位置以及低涡中心强度这几方面的具体分析,得到以下几点结论:1)HVW识别方法能够有效识别出高精度格点资料中的西南低涡过程,与格点实况的吻合率达到87.5%;对于天气图和格点资料都能够再现的西南低涡个例,HVW识别方法的准确度能够达到90.9%,说明HVW识别方法能够有效捕捉西南低涡。2)以天气图实况资料为西南低涡生命时长检验标准,HVW识别方法能够合理分析低涡的生成和消亡时间。3)对西南低涡中心位置偏差进行分析发现,HVW识别的西南低涡中心位置不仅位于西南低涡气压低值附近,更位于风场辐合中心。4)对西南低涡中心强度的评估发现,格点实况与HVW识别方法分析的西南低涡强度差异几乎可以忽略,充分说明了HVW识别方法包含了格点实况的高度场信息,也说明该识别方法的西南低涡中心强度可以用来代替格点实况结果。通过对2014年6—8月西南低涡过程的具体分析,验证了HVW逐步循环定位方法的可行性、合理性以及准确性。     

An algorithm to retrieve precipitation with synthetic aperture radar

This paper presents a new type of rainfall retrieval algorithm, called the model-oriented statistical and Volterra integration. It is a combination of the model-oriented statistical (MOS) and Volterra integral equation (VIE) approaches. The steps involved in this new algorithm can be briefly illustrated as follows. Firstly, information such as the start point and width of the rain is obtained through pre-analysis of the data received by synthetic aperture radar (SAR). Secondly, the VIE retrieval algorithm is employed over a short distance to obtain information on the shape of the rain. Finally, the rain rate can be calculated by using the MOS retrieval algorithm. Simulation results show that the proposed algorithm is effective and simple, and can lead to time savings of nearly 50% compared with MOS. An example of application of SAR data is also discussed, involving the retrieval of precipitation information over the South China Sea.     

光流法及其在临近预报中的应用

基于多尺度IVAP(MIVAP,the Multi-scale Integrating Velocity Azimuth Process)方法反演风场进行临近外推的预报方法原理可以概括为：首先采用大尺度的分析单元通过IVAP(Integrating Velocity Azimuth Process)方法得到反演风场作为引导气流,表示雷暴的系统性移动,再通过小尺度的分析单元来反演风场,作为雷暴内部移动信息的表征,最后将不同尺度的风场进行合成得到外推的运动矢量场以进行临近预报。相比传统的多尺度TREC(MTREC,the Multi-scale Tracking Radar Echoes by Correlation)方法依赖于追踪回波过去的变化,需要相邻一个或者几个时次的雷达回波来跟踪雷达回波的移动,使用MIVAP方法外推预报只需要最新时刻的雷达反射率因子和径向速度。通过个例分析和统计分析,并且与MTREC方法进行对比试验,结果表明：MIVAP方法反演风场用于临近外推预报具有可行性,MIVAP方法具有实际应用的意义;MIVAP方法得到的外推运动矢量场方向要比MTREC方法方向总体整体偏右,且外推的平均速度要比MTREC方法快;MIVAP方法在30 min以内前几个时次的预报效果略低于MTREC方法,但是30 min以后的预报评分明显优于MTREC方法,MIVAP方法的检验评分整体要优于MTREC方法。

     

冰雹云“酝酿”期研究

本文提出了冰雹云单体生命史中“酝酿”期的概念、现象和事实。文章还指出了“酝酿”期的特征和物理意义。     

一个相对精确计算沙瓦特指数方案的实现

在对流性天气的预报工作中,沙瓦特指数是一个被广泛应用的物理量,准确、快捷计算该指数一直以来都具有重要的实际意义。根据干、湿绝热过程相当位温守恒的原理,运用David Bolton给出的系列公式计算凝结温度、相当位温,利用计算机编程实现了应用探空资料自动、准确计算沙瓦特指数。11个实例的计算表明,与其他5种沙瓦特指数计算方案相比,新方案计算简洁、绝对误差的平均值与最大值均有所减小。其可能的原因是,计算中间过程避免了繁琐的数学推导和多次近似处理,且抬升凝结温度、相当位温等重要物理量计算比较准确。利用2010-2011年湖北省汉口站MICAPS格式探空资料,对比了查表法与新计算的沙瓦特指数对有、无雷暴天气的预示作用。结果表明：如果规定该指数小于零时有雷暴,则计算得出的数据可以较好地减少雷暴漏报。文中还指出了应用该指数时的局限性。     

Study of method for synthetic precipitation data for ungauged sites using quantitative precipitation model

A method was developed to estimate a synthetic precipitation record for ungauged sites using irregular coarse observations. The proposed synthetic precipitation data were produced with ultrahigh hourly resolution on a regular 1 × 1 km grid. The proposed method was used to analyze selected real-time observational data collected in South Korea from 2010 to the end of 2014. The observed precipitation data were measured using the Automatic Weather System and Automated Synoptic Observing System. The principal objective of the proposed method was to estimate the additional effects of orography on precipitation introduced by ultrahigh- resolution (1 × 1 km) topography provided by a digital elevation model. The Global Forecast System analysis of the National Centers for Environmental Prediction was used for the upper-atmospheric conditions, necessary for estimating the orographic effects. Precipitation data from 48 of the more than 600 observation sites used in the study, which matched the grid points of the synthetic data, were not included in the synthetic data estimation. Instead, these data were used to evaluate the proposed method by direct comparison with the real observations at these sites. A bias score was investigated by comparison of the synthetic precipitation data with the observations. In this comparison, the number of Hit, False, Miss, and Correct results for 2010-2014 was 74738, 25778, 7544, and 367981, respectively. In the Hit cases, the bias score was 1.22 and the correlation coefficient was 0.74. The means of the differences between the synthetic data and the observations were 0.3, -3.9, -14.4, and -34.9 mm h^-1 and the root mean square errors (RMSEs) were 2.7, 8.3, 19.3, and 39.6 mm h^-1 for the categories of 0.5-10.0, 10.0-30.0, 30.0-50.0, and 50.0-100.0 mm h^-1, respectively. In addition, in each range, the 60% difference between the synthetic precipitation data and the observation data was -1.5 to +1.5, -5.0 to +5.0, -17.0 to +17.0, and -33.0 to +33.0 mm h^-1, respectively. Overall, the correlation coefficient of the synthetic precipitation data was > 0.7 for 43 of the 48 test stations and the RMSE was < 4 mm h^-1 at 31 stations. The results are significant at all evaluation stations at the 0.05 significance level.     

多普勒天气雷达识别低空风切变算法的改进研究

针对CINRAD-CD天气雷达切变线识别产品的局限性,通过对探测资料采取中值滤波、滑动平均等预处理方法,有效填充缺测区探测资料。随后,再对探测资料采用最小二乘拟合法计算得到风场径向速度的径向切变、方位切变及垂直切变,进一步得到风场径向和方位的组合切变,从而得到垂直切变图。通过两次银川降雨过程实例应用,证明上述方法能够较准确地辨识风切变线,可为临近预报提供更科学的参考信息。     

合成孔径雷达森林资源监测技术研究综述

合成孔径雷达（Synthetic Aperture Radar,SAR）技术凭借其全天时、全天候的成像能力以及对森林垂直结构信息敏感的特点,在森林资源监测中具有独特的优势,已成为当前森林资源遥感调查技术的研究热点.本文首先介绍了SAR森林资源监测技术的发展背景、发展轨迹和相关知识;然后,重点阐述了极化SAR、干涉SAR、极化干涉SAR和层析SAR在林地覆盖类型分类、变化检测以及森林参数定量化估测应用中的技术方法;最后,就SAR在森林资源监测研究和应用中存在的问题与发展趋势进行了总结与展望.     

A comparative study on synthetic aperture radar and optical imagery of ocean waves

This note describes estimation of the zero-plane displacement derived from experimental windspeed measurements above an 18 m pine forest and an 8–9 m savannah using a ‘mass conservation technique’ mentioned by Tajchman (1981). The results obtained using this analysis exhibit a lack of sensitivity to experimental errors which is in marked contrast to those commonly obtained over tall vegetation using more conventional least-square analyses. The consistency in the results allows an investigation of the windspeed dependence of the aerodynamic properties of the mean horizontal airflow over tall vegetation, and permits consideration of the effect of experimental errors on such dependence.     

Calibration of weather radar using region probability matching method (RPMM)

In this paper, spatiotemporal variability of drought in Xilingol grassland during pasture growing season (from April to September) was investigated, using 52 years (1961–2012) of precipitation data recorded at 14 rain gauge stations in the study area. The Standardized Precipitation Index was used to compute the severity of drought. The Mann-Kendall test, the linear trend, and the sequential Mann-Kendall test were applied to standardized precipitation index (SPI) time series. The results indicate that drought has become increasingly serious on the region scale during pasture growing season, and the rate of SPI decreases ranged from ?0.112 to ?0.013 per decade. As for the MK test, most of the stations, the Z value range is from ?1.081 to ?0.005 and Kendall’s τ varies from ?0.104 to ?0.024. Meanwhile, drought is increased obviously from the northwest to the southeast region. Meanwhile, the occurrence probability of each severity class, times for reaching different drought class from any drought severity state, and residence times in each drought class have been obtained with Markov chain. Furthermore, the drought severities during pasture growing season in 2013–2016 are predicted depending on the weighted Markov chain. The results may provide a scientific basis for preventing and mitigating drought disaster.