基于济南地区的对流层湿延迟模型对比研究

为提高济南地区对流层路径湿延迟测量精度,改善此地区大气折射修正误差,进一步提高该地区导航、定位、测控雷达等无线电测控系统的精度和性能,文中以济南站全球电信系统（Global Telecommunications System,GTS）探空数据计算的天顶湿延迟、斜路径湿延迟为比较基准,比较分析了利用Marcor技术、Hopfield模型、Ifadis模型所得到的对流层天顶湿延迟和斜路径湿延迟.比较结果表明:利用Marcor技术所得到的天顶湿延迟和斜路径湿延迟比其他模型得到的精度高,且仰角越低,斜路径湿延迟相对精度越高.这表明Marcor技术在济南地区具有很强的适用性,是获取高精度对流层湿延迟有效手段之一,有望逐步取代气象探空技术在工程中应用.     

低仰角下对流层散射斜延迟估计方法

对流层斜延迟是对流层散射双向时间比对系统的主要误差来源,目前尚未有对系统中对流层斜延迟进行精确估计的模型。为精确估计斜延迟,引入电磁波射线描迹法,并利用Hopfield天顶延迟模型中折射率计算方案改进描迹法,以克服该方法对探空数据的依赖。首先,根据北纬35 ~37范围内的3个测站2010~2012年的实测气象数据和天顶延迟数据,验证 模型精度范围小于35 mm;然后,将3个测站按相互基线距离的不同分为3组比对站,利用改进后的模型结合2012年的气象数据,计算了在0~5入射角下,一年的斜延迟,并得出最大斜延迟对应的年积日和入射角。计算结果表明,3组比对站的最大单向斜延迟为24.94~45.37 m。在双向比对抵消90%的情况下,时间延迟为3.1~5.7 ns;相互抵消95%时,时间延迟为1.5~2.9 ns。     

基于改进射线描迹法的对流层斜延迟估计

该文针对传统对流层延迟模型和射线描迹法在估计对流层延迟方面的局限性,如效率低、成本高、精度受地表参数和探空数据限制等不足,提出一种基于改进射线描迹法的对流层斜延迟估计方法。该方法结合中纬度大气模式气象参数公式和UNB3m气象参数模型,改进了射线描迹法中折射率剖面的计算,克服了气象数据对射线描迹法的限制。选取亚洲地区10个站点2012年的气象数据,分别采用改进射线描迹法和传统对流层延迟模型估计各个站天顶方向至 高度角区间15个方向的对流层斜延迟,并与基于探空数据获取的对流层斜延迟真值进行比较,计算结果表明该方法的估计精度优于传统对流层延迟模型,为非气象数据情况下对流层斜延迟实时估计提供了新的思路。     

地球科学激光测高系统大气延迟修正算法

为了对大气传播延迟误差进行修正,达到精确测量的目的,推导了天顶延迟的理论计算公式;在大仰角情况下提出了一种简化的映射函数,并把它与连分式映射函数进行了比较。以地球科学激光测高系统在南极的观测数据为依据,分析得到该系统的平均大气延迟量为2.35m,修正误差控制在12mm以内。结果表明,在大仰角情况下,两者对总延迟的影响差异不超过0.1mm。总的延迟量可以通过天顶延迟和映射函数计算得出。     

利用RTKLIB提取对流层延迟方法与精度评估

全球卫星导航系统可以进行精确的水汽估算，能够成功地应用于天气预报中，比如数值天气预报模型。利用精密单点定位技术提取天顶对流层延迟，采用 RTKLIB 开源软件进行静态精密单点定位解算并提取天顶对流层延迟估值，并与国际 GNSS 服务 IGS 提供的参考值进行比较，评估其对流层解算精度。选取中国 3 个 IGS 观测站数据进行试验，结果表明 RTKLIB 可以获得厘米级的对流层解算精度。     

利用新型经验函数模拟云底亮温及误差分析

Stephen在2008年提出了一种新型亮温经验函数,为反演云底高提供了一种无需计算大气中实时水汽含量的新方法.利用SBDART模式和Stephen亮温函数比较系统地研究了不同天顶角、水汽、云、气溶胶、能见度等气象要素条件下,云底红外亮温Tb随天顶角的变化情况,并对其进行误差分析.模拟结果显示,水汽、云、天顶角及能见度小于5 km时对Tb影响较大,不同气象要素条件下,Stephen亮温函数模拟的云底亮温与SBDART模拟结果相近,所以,采用Stephen亮温函数模拟云底亮温具有可行性.     

铁路通信数据HBase分布式查询系统设计

目前设计的铁路通信数据分布式查询系统响应时间存在较大延迟,不具备实时性。为了解决上述问题,基于HBase设计了一种新的铁路通信数据分布式查询系统。配备三台主机,构建分布式查询模式,通过Linux组件和HDFS目录构建集群,同时建立数据存储模块和数据查询模块。利用HBase存储算法设定存储模型,得到逻辑片段集合,通过分析逻辑关系实现存储调度。实验结果表明,设计的基于HBase的铁路通信数据分布式查询系统数据写入性能响应延迟时间低于0.2 ms,缓冲性能写入延迟时间低于0.1 ms,能够很好地保证查询实时性。     

新长Z文件气象资料应用分析系统

新长Z文件气象资料应用分析系统应用Delphi7.0与SQL SERVER 2005相结合,采用SQL结构化数据查询语言,建立起基于C/S方式地自动气象站资料应用系统。系统利用现有的气象业务内网,将自动气象站资料纳入SQL SERVER 2005进行统一的数据管理。实现了自动气象站数据的处理入库、共享、实时数据监测、查询、统计等功能。     

流星突发通信数据采集网的研究

本文以边远地区自动水文、气象数据采集网为对象进行流星突发通信系统组网研究,利用流星余迹的空间特性完成了网络内部结构的设计;为提高通信的有效性提出了子群查询,全应答和逐址查询相结合的网络多址协议;将点对点通信系统中用以评价系统性能的平均等待时间等概念在网通信中作了推广。分析与计算的结果表明,本文所设计的系统要优于美国同类SNOTEL系统。     

基于地面宽带网络的气象数据传输系统

针对当前国内气象通信系统受卫星通信干扰所带来的数据缺失,传输延迟等问题,分析如何依托现有地面宽带资源,通过错峰利用,提高现有宽带网络使用效率,实现远程资源获取.满足气象数据传输的时效性、准确性要求,弥补气象数据卫星广播系统的不足,实现网络资源的高效利用.     

A three-year study of radio wave propagating delays due to tropospheric water vapor

Measurements of the radio emission from the sky at 21.0 and 31.4 GHz have been made from May 1980 to April 1983 at the Onsala Space Observatory on the west coast of Sweden. A total of 483 such observations have been used to calculate the water vapor induced propagation delay of radiowaves penetrating the troposphere. A comparison with simultaneous radiosonde launches made at Gothenburg-Landvetter Airport (37 km away from Ousala) gives a root mean square (rms) difference of 1.3 cm in the zenith direction and 1.1 cm for a certain group of stable weather data. The zenith wet path delays are also calculated with three different models based on traditional meteorological observations at the surface. The lowest rms difference obtained by using a model and compare the results with radiosonde data at the same site was 2.1 cm. A third site on the Swedish west coast was compared with the other two by using old monthly means of radiosonde data together with the three models. The offsets between the models and the radiosonde/water vapor radiometer (WVR) data are dependent on the model, on the site, and on the time of the year.     

Design, development, and initial measurements of a 1.4-mm radiometric system

The development of a 1.4-mm heterodyne radiometric system and the initial measurements taken with it are described. TheDelta Tof the system at the antenna terminals was approximately18.5degK for a 0.25-Hz post-correlation noise bandwidth. Measurements show that the attenuation through the atmosphere at this wavelength is primarily due to water vapor, and an estimate of the zenith attenuation is given byA (dB)= 2.8w, wherewis the precipitable water in centimeters. Measurements of the antenna half-power beamwidths using the sun as a source show that at 1.4 mm the atmospheric turbulence effects are not appreciable for observations through the atmosphere at zenith angles less than45degwith a 15-foot antenna.     

Tropospheric wet path-delay measurements

A dual-channel microwave radiometer measuring the sky brightness temperature at the frequencies 21.0 and 31.4 GHz, an infrared spectral hygrometer (IRSH) measuring the ratio of the radiation from the sun at the wavelengths 931 and 880 nm, and radiosondes have been used simultaneously to determine the excess path length due to water vapor (wet path delay) of radio waves propagating through the troposphere. By a least squares fit of the measured parameters from the microwave radiometer and the infrared spectral hygrometer, respectively, to the wet path delay calculated from the radiosonde profiles, the following root mean square (rms) differences of the wet path delay in the zenith direction were obtained: infrared spectral hygrometer-radiosondes, 1.1 cm; microwave radiometer-radiosondes, 0.7 cm; and 0.5 cm for a selected group of "good weather" data. The wet path delay was also calculated from surface meteorological measurements alone and the rms difference compared with corresponding radiosonde data was 2.0 cm in the zenith direction.     

基于Delphi的蒸发冷却空调查询系统开发

对Delphi数据库做了简单的介绍,掌握各种控件的功能属性,进行合理的界面设计,并且创建有效地数据库数据源,通过对数据库的管理等实现用户需要的新软件。简述了蒸发冷却空调技术应用。搭建出了关于Delphi和蒸发冷却的应用平台;设计出了关于气象资料、方案选择、设备资料的用户界面;实现了气象资料的查询功能。     

Ground-Based Microwave Radiometric Observations of the Temporal Vanation of Atmospheric Geopotential Height and Thickness

Since 1981, the Wave Propagation Laboratory of NOAA has operated a ground-based zenith-viewing microwave radiometer. This radiometer, designed to measure precipitable water vapor, cloud liquid, and temperature profiles, has two moisture-sensing channels and four temperature-sounding channels. Data from this system, taken at Denver, Colorado, are used to derive geopotential heights and thicknesses from the surface (about 830 mbar) to 300 mbar. Time series and spectra of several directly measured and inferred quantities are analyzed for different meteorological situations: a period of unusual calm in surface pressure, a frontal passage, and a gravity wave event. The three cases presented illustrate how rapid variations in meteorological variables can be studied using ground-based radiometers. These radiometers provide temporal continuity not hitherto available. The performance of the radiometer, both in observing a blackbody target and during an unusually calm pressure event, shows high sensitivity to changes in geopotential height and thickness and to integrated water vapor. Consequently, the combination of high temporal resolution and high sensitivity allows unique monitoring of rapidly changing conditions, such as frontal passages and gravity wave events. Comparisons of these data with various sources of ground truth, including radiosondes, satellite cloud observations, and arrays of microbarographs, show excellent agreement.     

The microwave radiometer aboard ERS-1. II. Validation of thegeophysical products

For pt.I see ibid., vol.31, no.6, p.1186-98 (1993). The ERS-1 microwave radiometer was designed to correct the satellite altimeter data for the excess path delay due to tropospheric humidity. The brightness temperature calibration was tested using two radiative transfer models, applied to the same coincident meteorological profiles over ocean. Differences were analyzed by similarly comparing calculated brightness temperatures with SSM/I data, for the same meteorological data set, extracted from ECMWF (European Center for Medium range Weather Forecasting) analyses. The calibration of the two channels of the ERS-1 microwave radiometer required correction of a few Kelvin. The final water vapor and altimeter path delay validation was performed by comparing routine radiosonde measurements with the retrieved water vapor and altimeter path corrections over a one-year period     

Sky brightness temperature measurements at 135 GHz and 215 GHz

Zenith sky brightness temperature measurements at 135 GHz and 215 GHz have been made on a semicontinuous basis for a period of seven months in the Gunston Cove area of Northern Virginia. These measurements were made using Dicke receivers with noise figures of 8 dB and 14 dB, respectively. A liquid nitrogen cooled load was used to calibrate the measurements. The 215 GHz sky temperature was on the average about 80 K greater than that at 135 GHz. Clouds were found to cause the sky temperatures to fluctuate as much as 150 K in a few minutes. Graphs are presented to outline general trends of the data as well as representative days, including the blizzard on February 11, 1983. In addition, empirical relations between precipitable water vapor, atmospheric water density at the surface, sky brightness temperatures, and zenith attenuation are given for visually clear days.     

DTF型太阳光度计测量大气光学参数的对比验证及误差分析

DTF型系列太阳光度计在合肥地区测量大气气溶胶光学厚度(AOT)和可降水量(PWV),并与其它测量仪器进行对比验证,各仪器之间测量结果日变化趋势具有很好的一致性.对比分析结果显示:太阳光度计之间测量气溶胶光学厚度和可降水量的均方根误差都在8％以内;太阳光度计测量的可降水量与微波辐射计测量的水汽含量进行对比,均方根误差约5％.通过对比验证和误差分析,DTF型太阳光度计测量AOT和PWV具有较高的可靠性.