一次冰雹云天气过程不同波段雷达回波对比分析

选取一次降雹天气过程,采用贵阳C波段雷达和移动X波段雷达数据,通过分析两部雷达回波强度的空间分布、时间变化波动等特征参量,以验证在复杂山地环境下,移动X波段天气雷达对冰雹云天气过程的探测效果。     

广州相控阵天气雷达组网站址分析

X波段双偏振相控阵天气雷达在观测中小尺度天气系统方面具有优势,然而在反射率因子超过一定值之后,有效探测距离会急剧下降。利用雷达组网建设,能确保有效探测,提高观测数据质量。根据相关文献资料,结合2018年5月7日广州暴雨过程,得出组网观测系统中的X波段相控阵天气雷达彼此间隔为35～45 km,基于此间距,通过综合分析,明确广州X波段双偏振相控阵天气雷达组网建设站址。     

威宁X波段双偏雷达与昭通C波段天气雷达回波强度对比

为了能够更加准确地预警贵州威宁及其周边地区的冰雹和其他强对流天气过程,尽可能多的减小各型雷达回波强度的差异,以昭通C波段天气雷达为基准,选取昭通C波段天气雷达和威宁X波段双偏雷达同步观测体扫资料,对3组强对流天气过程回波特征进行了详尽的对比分析,结果表明:威宁X波段双偏雷达与昭通C波段天气雷达回波强度测量值存在一定的误差,前者回波强度整体较后者偏大;观测目标距离两者越近回波强度误差值越小,反之越大;两者对距离较近的观测目标回波强度值一致性较好。     

移动X波段双线偏振雷达数据质量分析及偏差订正

2019年8月,中国电子科技集团第十四研究所南京恩瑞特实业有限公司研制的GLC-12A型移动X波段双线偏振多普勒天气雷达在江苏大丰进行外场观测。根据该雷达外场观测资料,联合盐城新一代SA天气雷达和江苏省6个雨量站资料,对移动X波段双线偏振雷达做数据质量分析。结果表明,针对同一次降水过程而言,距离越远,衰减越大。为了降低衰减造成的观测误差,首先利用信噪比对差分反射率Z_dr、零滞后相关系数ρhv(0)进行偏差订正,提高Z_dr和ρhv(0)的数据质量,以便进行地杂波、生物回波等非降水回波过滤。然后应用去抖动滤波后的差分传播相移率K dp或总差分传播相位Φdp表达在雨中距离雷达R处的总双向反射率因子衰减订正值。数据分析表明,订正后移动X波段双线偏振雷达数据质量得到了提高。     

X波段双偏振多普勒天气雷达降雨估算试验

用X波段双偏振多普勒天气雷达和RG3-M型自动采集翻斗式雨量计,经过严格科学设计,在平凉野外布置试验场,采用与天气系统移动方向一致的两次层积云资料,验证X波段双偏振多普勒天气雷达的测雨能力。试验表明:雷达原始数据滤波处理的好坏直接影响降雨估算精度的高低,特别是对R(Kdp)和R(Kdp,Zdr)影响明显,滤波后数据点的空间平滑是必要的;发展了用雨量计反演雷达测雨参数方法,此方法改进了不同地区、不同雨滴谱分布情况下雷达定量测雨能力;同时表明X波段雷达受降雨衰减的影响比较严重,这些试验结果可作为下一代测雨天气雷达的重要参考依据。     

X波段天气雷达电磁辐射对环境影响的评估

为了定量分析X波段天气雷达电磁辐射对环境的影响,依据X波段天气雷达的主要性能参数,理论推导X波段天气雷达的电磁辐射特性,分析X波段雷达站点周边环境,对电磁辐射进行水平和垂直立体监测,理论计算和实际监测结果均表明X波段雷达电磁辐射大小满足《电磁环境控制限值》(GB8702—2014)和《辐射环境保护管理导则电磁辐射监测仪器和方法》(HJ/T10. 2—1996)的要求,电磁辐射水平低于公众曝露的控制限值。     

多部X波段天气雷达测量偏差分布及组网拼图结果分析北大核心CSCD

在与附近新一代天气雷达对比的基础上,利用自2013年6月起中国科学院大气物理研究所的三部X波段天气雷达在江苏开展了组网观测试验的观测资料,初步对雷达的探测能力和雨区衰减做了分析和订正,同时使用了中国气象科学研究院三维组网系统,将X波段天气雷达与业务雷达资料组网,探索了X波段天气雷达的对业务雷达的补充效果。结果表明:(1)X波段天气雷达的观测数据分别受到了地物回波、遮挡及雨区衰减的影响,已对基数据做了初步的质量控制;(2)通过回波结构和廓线图的对比,经地物抑制、衰减汀正等方法质控后的数据存一定范围内具有较高的可靠性,同时三部X波段天气雷达能够有效探测到60 km内的降水结构,其回波分布较为合理,准确的反映了降水区域的特征;(3)将三部X波段天气雷达观测资料与业务中的新一代天气雷达组网后,得到了结构连续、分布更广、平滑作用更低的资料,补充了新一代天气雷达的低空盲区。     

多部X波段天气雷达测量偏差分布及组网拼图结果分析

在与附近新一代天气雷达对比的基础上,利用自2013年6月起中国科学院大气物理研究所的三部X波段天气雷达在江苏开展了组网观测试验的观测资料,初步对雷达的探测能力和雨区衰减做了分析和订正,同时使用了中国气象科学研究院三维组网系统,将X波段天气雷达与业务雷达资料组网,探索了X波段天气雷达的对业务雷达的补充效果。结果表明:(1)X波段天气雷达的观测数据分别受到了地物回波、遮挡及雨区衰减的影响,已对基数据做了初步的质量控制;(2)通过回波结构和廓线图的对比,经地物抑制、衰减汀正等方法质控后的数据存一定范围内具有较高的可靠性,同时三部X波段天气雷达能够有效探测到60 km内的降水结构,其回波分布较为合理,准确的反映了降水区域的特征;(3)将三部X波段天气雷达观测资料与业务中的新一代天气雷达组网后,得到了结构连续、分布更广、平滑作用更低的资料,补充了新一代天气雷达的低空盲区。     

X波段移动全相参多普勒雷达应用及与C波段新一代天气雷达对比

本文根据2010年8月10日12:00至8月12日12:00在呼兰地区连续48h观测得到的移动X波段全相参多普勒天气雷达的数据,讨论了该移动雷达在两个方面的应用情况:一是根据移动雷达观测150km范围内得到的回波进行全方位跟踪、识别;二是对该移动雷达观测结果在强度场、速度场以及回波高度、回波位置与距离30km的C波段3...     

我国地基天气雷达技术系统发展介绍

回顾了我国天气雷达从常规雷达发展到单极化多普勒,再到双极化多普勒,雷达获取目标的参数信息更加丰富的过程。分析了常规、单极化多普勒、双极化多普勒雷达工作原理及其产品信息。对于我国新一代S、C和X波段的天气雷达性能进行了研究对比。阐述了毫米波段多普勒测云雷达工作原理及其产品。对新一代天气雷达网进行了分析及展望,双极化将是我国天气雷达网升级改造趋势,为弥补新一代天气雷达探测盲区,小型移动电扫描雷达也是一种辅助主雷达网可移动灵活布网的趋势。     

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.     

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.     

宁波地区海-陆下垫面差异对雷暴过程影响的数值模拟

利用耦合Noah陆面过程的WRF模式对2009年6月5日傍晚发生在宁波地区的一次雷暴过程进行数值模拟,通过改变下垫面覆盖类型的敏感性试验,探讨了海洋和陆地下垫面对雷暴过程的影响。结果表明,WRF模式能够较合理地模拟出雷暴的发生、发展过程。雷暴发生前期,由于海-陆强烈的热力差异,海风特征明显,海风引起的抬升运动触发了雷暴,海风形成的强辐合区对应雷暴过程累积降水量的大值区。当研究区域全部被替换成陆地后,地表的粗糙度增大,在研究区域东部由于摩擦辐合加强,产生了强烈的上升运动,多个发展旺盛的对流单体在上升运动区生成,使雷暴产生的降水区域东扩、降水量增大、雷暴维持时间延长。当研究区域所有陆地被替换成水体后,白天地表通量减小,大气边界层中湍流运动减弱,边界层高度降低,大气层结变得稳定,不利于对流发展。     

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.     

淮河流域水文极值预测模型研究

为探索气候变化影响下水文极值的非平稳性和预测方法,建立了水文极值非平稳广义极值（GEV）分布的统计预测模型。利用1952-2010年淮河上游流域累计面雨量和流量年最大值资料、同期500 hPa环流特征量资料以及17个CMIP5模式对环流特征量的模拟结果,筛选出对水文极值影响显著的年平均北半球极涡强度指数作为GEV分布参数的预测因子。分析了在RCP2.6、RCP4.5和RCP8.5情景下2006-2050年淮河上游流域水文极值对气候变化的响应。结果表明,10年以下与10年以上重现期的水文极值在非平稳过程中呈现前者下降而后者上升的相反变化趋势;多模型预测的集合平均在未来情景中均呈现上升趋势,情景排放量越大增幅越大,重现期越长增幅也越大。与极值的常态相比,极值的极端态更易受气候变化影响。     

Light-absorbing particles in snow and ice: Measurement and modeling of climatic and hydrological impact

Light absorbing particles(LAP, e.g., black carbon, brown carbon, and dust) influence water and energy budgets of the atmosphere and snowpack in multiple ways. In addition to their effects associated with atmospheric heating by absorption of solar radiation and interactions with clouds, LAP in snow on land and ice can reduce the surface reflectance(a.k.a., surface darkening), which is likely to accelerate the snow aging process and further reduces snow albedo and increases the speed of snowpack melt. LAP in snow and ice(LAPSI) has been identified as one of major forcings affecting climate change, e.g.in the fourth and fifth assessment reports of IPCC. However, the uncertainty level in quantifying this effect remains very high. In this review paper, we document various technical methods of measuring LAPSI and review the progress made in measuring the LAPSI in Arctic, Tibetan Plateau and other mid-latitude regions. We also report the progress in modeling the mass concentrations, albedo reduction, radiative forcing, and climatic and hydrological impact of LAPSI at global and regional scales. Finally we identify some research needs for reducing the uncertainties in the impact of LAPSI on global and regional climate and the hydrological cycle.     

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.     

Data selection using support vector regression

Geophysical data sets are growing at an ever-increasing rate, requiring computationally efficient data selection(thinning)methods to preserve essential information. Satellites, such as Wind Sat, provide large data sets for assessing the accuracy and computational efficiency of data selection techniques. A new data thinning technique, based on support vector regression(SVR), is developed and tested. To manage large on-line satellite data streams, observations from Wind Sat are formed into subsets by Voronoi tessellation and then each is thinned by SVR(TSVR). Three experiments are performed. The first confirms the viability of TSVR for a relatively small sample, comparing it to several commonly used data thinning methods(random selection, averaging and Barnes filtering), producing a 10% thinning rate(90% data reduction), low mean absolute errors(MAE) and large correlations with the original data. A second experiment, using a larger dataset, shows TSVR retrievals with MAE < 1 m s-1and correlations 0.98. TSVR was an order of magnitude faster than the commonly used thinning methods. A third experiment applies a two-stage pipeline to TSVR, to accommodate online data. The pipeline subsets reconstruct the wind field with the same accuracy as the second experiment, is an order of magnitude faster than the nonpipeline TSVR. Therefore, pipeline TSVR is two orders of magnitude faster than commonly used thinning methods that ingest the entire data set. This study demonstrates that TSVR pipeline thinning is an accurate and computationally efficient alternative to commonly used data selection techniques.     

前寒武纪气候演化中的三个重要科学问题

自地球形成至寒武纪将近40亿年（距今46亿～5.4亿年,通常称为前寒武纪）的气候演变是一个具有特殊难度和挑战性的研究领域,同时也是基础和前沿的研究领域。文章选择了前寒武纪气候演化中的三个重要科学问题进行综述：大气演化、两次全球性的冰川期以及暗弱太阳问题。关于大气演化,本文首先描述了大气成分的演化历史,然后简述了影响大气成分演化的三个基本过程：大气逃逸、两次大气氧含量突然增加、碳酸盐-硅酸盐循环及其对气候系统的负反馈作用。两次全球性的冰川期分别发生在古元古代（距今24亿～21亿年）和新元古代（距今8亿～5.8亿年）,文章简述了其成因以及相关的气候模拟结果。暗弱太阳问题是地球历史气候演化的一个经典问题,论文简要地综述了一些最新的研究成果和观点。