CINRAD/SA雷达发射机驱动级工作原理及检修技术探讨

新一代多普勒天气雷达CINRAD/SA发射机放大链驱动级是发射机中的关键部件,占有很重要的地位,其技术指标基本决定了发射机的输出高频脉冲宽度及频谱,直接影响雷达系统的质量。详细讨论了发射机放大链驱动级的硬件组成及工作原理,并对其相关线路作了进一步分析,介绍了正确的调试方法,给出了几个关键点波形及相关时序,根据台站工作的实际经验,结合相关报警信息,探讨了基本维修思路,总结了一些快速有效的检修方法,希望能为新一代多普勒天气雷达技术保障提供有益的借鉴。     

CINRAD/SA发射机极限改善因子受干扰的成因分析

发射机极限改善因子是新一代天气雷达出厂验收测试的最重要的技术指标之一,它分为发射机输入极限改善因子和输出极限改善因子两项测试内容。参照普来赛西门子雷达公司提供的测试方法,用频谱仪检测信号功率谱密度分布,从中求取信号和相噪的功率谱密度比值(S/N)。然而在出厂验收测试和巡检中,发现不同频率的干扰毛刺出现在信号功率谱密度分布图上,它们可能会影响发射机极限改善因子的测量指标及发射机相位的稳定性等。文章从CINRAD/SA雷达发射机极限改善因子测试信号链路进行分析,查找干扰毛刺的产生原因及检测检修方法,为雷达技术保障人员提供现场维修和维护方面的经验。     

新一代天气雷达发射机常用芯片自动检测技术研究

目前气象业务中,新一代天气雷达组网建设不断完善,其在短时临近灾害性天气预报、预警业务和决策服务中越来越发挥着不可替代的重要作用,因此,做好新一代天气雷达的业务运行保障工作非常重要。针对新一代天气雷达发射机软硬件复杂、故障频发、维修时效长、维修难度大等特点,研制了新一代天气雷达发射机常用芯片自动检测系统。该自动检测系统采用了机外脱机测试方法,从而保证了雷达设备和人身的安全;采用了发光二极管指示灯直接输出测试结果的自动测试方式,保证了雷达修复的较短时效;可直接测试雷达组件内部电路板常用关键芯片的好坏,而不必更换整个笨重的分机组件备件,从而使维修新一代天气雷达发射机故障变得便捷、高效、经济。新一代天气雷达发射机常用芯片自动检测系统研制完成后在多个台站得到了试用,试用效果良好,可为其他新一代天气雷达站快速维修新一代天气雷达发射机提供借鉴和参考。     

利用微波功率传感器判断新一代天气雷达故障

近年来,以平面掺杂势垒二极管为核心构成的微波功率传感器与小功率计配合,能实现对微波功率的高速、高精度和连续测量,广泛应用于天气雷达等高频设备信号功率的测量。文章详细阐述了微波功率传感器的特性和电路原理,以及该传感器与小功率计的连接、设置和使用方法。并以在CINRAD/SA雷达发射机、接收机中两个典型故障检修事例,论述了微波功率传感器在天气雷达上的应用。     

713雷达的双线偏振改装

本文介绍了将713天气雷达改为双线偏振雷达的方法。即在713雷达上增加一只大功率微波开关,将天线馈源改为双通道,提高雷达发射机的脉冲重复频率和加设必要的数据处理系统后,使713雷达具有双线偏振探测能力。文中对各主要部件的技术指标亦作了介绍。     

CINRAD/SA雷达回扫充电控制电路调试技巧及故障处理

从济南新一代天气雷达CINRAD/SA的日常测试与调试工作出发,着重介绍了发射机同扫充电控制系统3A10组件的调试方法与注意事项,同时简述了实际工作中出现的常见故障、成因及其排除方法,旨在使技术保障人员掌握该雷达测试与调试的方法,能在最短的时间内排除设备故障,保障雷达处于良好的运转状态.     

湛江新一代天气雷达的调试

雷达的调试过程包括分系统调试、系统标定和拷机3个步骤.系统地介绍了湛江新一代多普勒天气雷达在调试过程中一些重要的标定方法、调试方法及相关的注意事项;最后列举了湛江新一代天气雷达在安装调试过程中遇到的诸多问题,以及相应的解决办法.     

CINRAD/CC型新一代天气雷达激励源故障分析

激励源是全相参多普勒天气雷达发射分系统射频激励调制脉冲信号和标定分系统射频测试调制脉冲信号的提供者,如果激励源输出的RF调制脉冲信号的功率下降比较多,或者时序控制脉冲幅度和脉宽发生变化,或者进入激励源的本振1、本振2的频率和功率发生变化,都将引起发射机发射功率的大幅度下降,从而造成回波信号异常等故障现象.通过2010年10月27日新疆阿克苏天气雷达激励源故障现象,并结合激励源的基本原理及雷达正常运行和非正常情况下关键点波形的对比分析揭示了CINAD/CC天气雷达激励源故障的成因,给出了故障诊断依据和测试排除的具体办法,为保证天气雷达业务实时运转提供了保障.     

新一代天气雷达（CB）发射机的检测与维修

随着全国新一代天气雷达网的建成,新一代天气雷达在气象服务中发挥的作用日益凸显。作为机电一体化的复杂系统,故障随着使用年限的增加日益增多,这与发射机长期处于高功率、大电流的工作状态有关。为了更好地维护天气雷达,提高维修时效,根据作者的工作经验,介绍常用检测方法和检测结果,并对常见故障进行分析,给出解决方案。     

新一代天气雷达发射机寄生频谱分析与处理方法

针对新一代天气雷达(CINRAD)发射机频谱中存在寄生谱线的现象,建立了雷达发射信号寄生调制的数学模型,根据CINRAD雷达发射机组成原理框图,分析了寄生谱线产生的原因,并提出了解决雷达发射机寄生谱线问题的方法,利用该方法在某CINRAD雷达系统联调和测试中基本消除了发射机输出频谱的寄生谱线,提高了发射机的频谱纯度.     

COMPARATIVE ANALYSIS OF VARIOUS DATA OF AIR–SEA TEMPERATURE DIFFERENCE AND ITS VARIATION ACROSS SOUTH CHINA SEA IN THE PAST 35 YEARS

Using the International Comprehensive Ocean-Atmosphere Data Set(ICOADS) and ERA-Interim data, spatial distributions of air-sea temperature difference(ASTD) in the South China Sea(SCS) for the past 35 years are compared,and variations of spatial and temporal distributions of ASTD in this region are addressed using empirical orthogonal function decomposition and wavelet analysis methods. The results indicate that both ICOADS and ERA-Interim data can reflect actual distribution characteristics of ASTD in the SCS, but values of ASTD from the ERA-Interim data are smaller than those of the ICOADS data in the same region. In addition, the ASTD characteristics from the ERA-Interim data are not obvious inshore. A seesaw-type, north-south distribution of ASTD is dominant in the SCS; i.e., a positive peak in the south is associated with a negative peak in the north in November, and a negative peak in the south is accompanied by a positive peak in the north during April and May. Interannual ASTD variations in summer or autumn are decreasing. There is a seesaw-type distribution of ASTD between Beibu Bay and most of the SCS in summer, and the center of large values is in the Nansha Islands area in autumn. The ASTD in the SCS has a strong quasi-3a oscillation period in all seasons, and a quasi-11 a period in winter and spring. The ASTD is positively correlated with the Nio3.4 index in summer and autumn but negatively correlated in spring and winter.     

CHARACTERISTICS AND TRENDS OF CLIMATIC EXTREMES IN CHINA DURING 1959–2014

The spatial and temporal variations of daily maximum temperature(Tmax), daily minimum temperature(Tmin), daily maximum precipitation(Pmax) and daily maximum wind speed(WSmax) were examined in China using Mann-Kendall test and linear regression method. The results indicated that for China as a whole, Tmax, Tmin and Pmax had significant increasing trends at rates of 0.15℃ per decade, 0.45℃ per decade and 0.58 mm per decade,respectively, while WSmax had decreased significantly at 1.18 m·s~(-1) per decade during 1959—2014. In all regions of China, Tmin increased and WSmax decreased significantly. Spatially, Tmax increased significantly at most of the stations in South China(SC), northwestern North China(NC), northeastern Northeast China(NEC), eastern Northwest China(NWC) and eastern Southwest China(SWC), and the increasing trends were significant in NC, SC, NWC and SWC on the regional average. Tmin increased significantly at most of the stations in China, with notable increase in NEC, northern and southeastern NC and northwestern and eastern NWC. Pmax showed no significant trend at most of the stations in China, and on the regional average it decreased significantly in NC but increased in SC, NWC and the mid-lower Yangtze River valley(YR). WSmax decreased significantly at the vast majority of stations in China, with remarkable decrease in northern NC, northern and central YR, central and southern SC and in parts of central NEC and western NWC. With global climate change and rapidly economic development, China has become more vulnerable to climatic extremes and meteorological disasters, so more strategies of mitigation and/or adaptation of climatic extremes,such as environmentally-friendly and low-cost energy production systems and the enhancement of engineering defense measures are necessary for government and social publics.     

IMPACT OF ATMOSPHERIC LOW-FREQUENCY OSCILLATION ON THE IMMIGRATION OF NILAPARVATA LUGENS(STL) IN HUNAN AND JIANGXI PROVINCES

Various features of the atmospheric environment affect the number of migratory insects, besides their initial population. However, little is known about the impact of atmospheric low-frequency oscillation(10 to 90 days) on insect migration. A case study was conducted to ascertain the influence of low-frequency atmospheric oscillation on the immigration of brown planthopper, Nilaparvata lugens(Stl), in Hunan and Jiangxi provinces. The results showed the following:(1) The number of immigrating N. lugens from April to June of 2007 through 2016 mainly exhibited a periodic oscillation of 10 to 20 days.(2) The 10-20 d low-frequency number of immigrating N. lugens was significantly correlated with a low-frequency wind field and a geopotential height field at 850 h Pa.(3) During the peak phase of immigration, southwest or south winds served as a driving force and carried N. lugens populations northward, and when in the back of the trough and the front of the ridge, the downward airflow created a favorable condition for N. lugens to land in the study area. In conclusion, the northward migration of N. lugens was influenced by a low-frequency atmospheric circulation based on the analysis of dynamics. This study was the first research connecting atmospheric low-frequency oscillation to insect migration.     

A COMPARATIVE ANALYSIS OF ATMOSPHERIC AND OCEANIC CONDITIONS BEFORE THE OCCURRENCE OF TWO TYPES OF EL NIO EVENTS

The atmospheric and oceanic conditions before the onset of EP El Ni?o and CP El Ni?o in nearly 30 years are compared and analyzed by using 850 hPa wind, 20℃ isotherm depth, sea surface temperature and the Wheeler and Hendon index. The results are as follows: In the western equatorial Pacific, the occurrence of the anomalously strong westerly winds of the EP El Ni?o is earlier than that of the CP El Ni?o. Its intensity is far stronger than that of the CP El Ni?o. Two months before the El Ni?o, the anomaly westerly winds of the EP El Ni?o have extended to the eastern Pacific region, while the westerly wind anomaly of the CP El Ni?o can only extend to the west of the dateline three months before the El Ni?o and later stay there. Unlike the EP El Ni?o, the CP El Ni?o is always associated with easterly wind anomaly in the eastern equatorial Pacific before its onset. The thermocline depth anomaly of the EP El Ni?o can significantly move eastward and deepen. In addition, we also find that the evolution of thermocline is ahead of the development of the sea surface temperature for the EP El Ni?o. The strong MJO activity of the EP El Ni?o in the western and central Pacific is earlier than that of the CP El Ni?o. Measured by the standard deviation of the zonal wind square, the intensity of MJO activity of the EP El Ni?o is significantly greater than that of the CP El Ni?o before the onset of El Ni?o.     

ANALYSIS OF “BIMODAL PATTERN” STORM ACTIVITY CHARACTERISTICS OF THE BAY OF BENGAL

Storms that occur at the Bay of Bengal (BoB) are of a bimodal pattern, which is different from that of the other sea areas. By using the NCEP, SST and JTWC data, the causes of the bimodal pattern storm activity of the BoB are diagnosed and analyzed in this paper. The result shows that the seasonal variation of general atmosphere circulation in East Asia has a regulating and controlling impact on the BoB storm activity, and the “bimodal period” of the storm activity corresponds exactly to the seasonal conversion period of atmospheric circulation. The minor wind speed of shear spring and autumn contributed to the storm, which was a crucial factor for the generation and occurrence of the “bimodal pattern” storm activity in the BoB. The analysis on sea surface temperature (SST) shows that the SSTs of all the year around in the BoB area meet the conditions required for the generation of tropical cyclones (TCs). However, the SSTs in the central area of the bay are higher than that of the surrounding areas in spring and autumn, which facilitates the occurrence of a “two-peak” storm activity pattern. The genesis potential index (GPI) quantifies and reflects the environmental conditions for the generation of the BoB storms. For GPI, the intense low-level vortex disturbance in the troposphere and high-humidity atmosphere are the sufficient conditions for storms, while large maximum wind velocity of the ground vortex radius and small vertical wind shear are the necessary conditions of storms.     

LOW-FREQUENCY CIRCULATION AND EXTENDED-RANGE FORECAST IN CONNECTION WITH AUTUMN EXTREME HEAVY RAINFALL PROCESS IN HAINAN

Observed daily precipitation data from the National Meteorological Observatory in Hainan province and daily data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis-2 dataset from 1981 to 2014 are used to analyze the relationship between Hainan extreme heavy rainfall processes in autumn (referred to as EHRPs) and 10–30 d low-frequency circulation. Based on the key low-frequency signals and the NCEP Climate Forecast System Version 2 (CFSv2) model forecasting products, a dynamical-statistical method is established for the extended-range forecast of EHRPs. The results suggest that EHRPs have a close relationship with the 10–30 d low-frequency oscillation of 850 hPa zonal wind over Hainan Island and to its north, and that they basically occur during the trough phase of the low-frequency oscillation of zonal wind. The latitudinal propagation of the low-frequency wave train in the middle-high latitudes and the meridional propagation of the low-frequency wave train along the coast of East Asia contribute to the ‘north high (cold), south low (warm)’ pattern near Hainan Island, which results in the zonal wind over Hainan Island and to its north reaching its trough, consequently leading to EHRPs. Considering the link between low-frequency circulation and EHRPs, a low-frequency wave train index (LWTI) is defined and adopted to forecast EHRPs by using NCEP CFSv2 forecasting products. EHRPs are predicted to occur during peak phases of LWTI with value larger than 1 for three or more consecutive forecast days. Hindcast experiments for EHRPs in 2015–2016 indicate that EHRPs can be predicted 8–24 d in advance, with an average period of validity of 16.7 d.     

AN ATTRIBUTION ANALYSIS OF CHANGES IN POTENTIAL EVAPOTRANSPIRATION IN THE BEIJING–TIANJIN–HEBEI REGION UNDER CLIMATE CHANGE

Based on the measurements obtained at 64 national meteorological stations in the Beijing–Tianjin–Hebei (BTH) region between 1970 and 2013, the potential evapotranspiration (ET0) in this region was estimated using the Penman–Monteith equation and its sensitivity to maximum temperature (Tmax), minimum temperature (Tmin), wind speed (Vw), net radiation (Rn) and water vapor pressure (Pwv) was analyzed, respectively. The results are shown as follows. (1) The climatic elements in the BTH region underwent significant changes in the study period. Vw and Rn decreased significantly, whereas Tmin, Tmax and Pwv increased considerably. (2) In the BTH region, ET0 also exhibited a significant decreasing trend, and the sensitivity of ET0 to the climatic elements exhibited seasonal characteristics. Of all the climatic elements, ET0 was most sensitive to Pwv in the fall and winter and Rn in the spring and summer. On the annual scale, ET0 was most sensitive to Pwv, followed by Rn, Vw, Tmax and Tmin. In addition, the sensitivity coefficient of ET0 with respect to Pwv had a negative value for all the areas, indicating that increases in Pwv can prevent ET0 from increasing. (3) The sensitivity of ET0 to Tmin and Tmax was significantly lower than its sensitivity to other climatic elements. However, increases in temperature can lead to changes in Pwv and Rn. The temperature should be considered the key intrinsic climatic element that has caused the "evaporation paradox" phenomenon in the BTH region.     

Could the Recent Taal Volcano Eruption Trigger an El Ni?o and Lead to Eurasian Warming?

正The Taal Volcano in Luzon is one of the most active and dangerous volcanoes of the Philippines. A recent eruption occurred on 12 January 2020(Fig. 1a), and this volcano is still active with the occurrence of volcanic earthquakes. The eruption has become a deep concern worldwide, not only for its damage on local society, but also for potential hazardous consequences on the Earth's climate and environment.     

Revisiting the Concentration Observations and Source Apportionment of Atmospheric Ammonia

正While China’s Air Pollution Prevention and Control Action Plan on particulate matter since 2013 has reduced sulfate significantly, aerosol ammonium nitrate remains high in East China. As the high nitrate abundances are strongly linked with ammonia, reducing ammonia emissions is becoming increasingly important to improve the air quality of China. Although satellite data provide evidence of substantial increases in atmospheric ammonia concentrations over major agricultural regions, long-term surface observation of ammonia concentrations are sparse. In addition, there is still no consensus on