Verification of RASS-measured temperature profiles using a radio-controlled model glider

Potential sonic temperature profiles from a continuous electromagnetic, pulsed acoustic, radio acoustic sounding system (RASS) were compared with profiles recorded by a commercially available temperature, relative humidity and pressure recorder mounted in a radio-controlled model motor-glider. The glider profiles covered the period of the morning transition in the lowest 200 m of an initially stably stratified boundary layer. Comparison of the profiles shows that the sonic temperature can be calculated based on the average speed of sound in the boundary layer; this removes the need to correct for vertical velocity in each temperature profile, thus avoiding the possibility of contaminating the temperatures with measurement noise from the vertical velocity profiles. Further, the low-level cold bias that occurs with the spatially separated transmit and receive antennas of a bistatic RASS system was not significant for the present measurements as the separation between the antennas was minimised. The comparison of RASS and glider temperatures gives confidence in the use of RASS-derived temperatures for investigating the performance of boundary layer models.     

Measuring Vertical Heat Flux with RASS

Summary A wind‐profiling Doppler radar equipped with a radio acoustic sounding system (RASS) may be used to estimate the vertical profile of the vertical flux of heat in the atmosphere. Simultaneous measurements of the time‐varying temperature and vertical air velocity are combined to give the convective heat flux using the eddy‐correlation method. The accuracy of the estimates depends on the fundamental accuracy of the temperature and vertical velocity measurements. Also, in common with all eddy‐correlation methods, uncertainties are introduced by the need to define a suitable averaging time and to remove trends. A problem unique to RASS is the possible presence of ground and intermittent clutter at close ranges, which can cause errors in the vertical air velocity measurements. These considerations are discussed with particular reference to observations using a UHF radar wind profiler situated in an urban environment, where clutter is a serious problem. A Rank‐Order Signal Processing Algorithm (ROSPA) for recognizing and eliminating outliers in the vertical velocity, is introduced. It is explained how ROSPA uses both a minimum filter and a median filter on the velocity data. It is shown, using a comparison with nearly clutter free data from a rural site, that the filtering substantially improves the quality of the noisy urban data. The paper then compares RASS‐measured urban and rural heat flux profiles, along with the heat flux profile measured by an instrumented airplane. It is concluded that the main obstacles to RASS heat flux measurements are the effects of winds and turbulence in the boundary layer, rather than clutter. Received September 24, 1998 Revised January 27, 1999     

Evaluation of the Interpretation of Ceilometer Data with RASS and Radiosonde Data

Since 2006 different remote monitoring methods for determining mixing-layer height have been operated in parallel in Augsburg (Germany). One method is based on the operation of eye-safe commercial mini-lidar systems (ceilometers). The optical backscatter intensities recorded with ceilometers provide information about the range-dependent aerosol concentration; gradient minima within this profile mark the tops of mixed layers. Special software for these ceilometers provides routine retrievals of lower atmospheric layering. A second method, based on sodar observations, detects the height of a turbulent layer characterized by high acoustic backscatter intensities due to thermal fluctuations and a high variance of the vertical velocity component. This information is extended by measurements with a radio-acoustic sounding system (RASS) that directly provides the vertical temperature profile from the detection of acoustic signal propagation and thus temperature inversions that mark atmospheric layers. Ceilometer backscatter information is evaluated by comparison with parallel measurements. Data are presented from 2 years of combined ceilometer and RASS measurements at the same site and from comparison with a nearby (60 km) radiosonde for larger-scale humidity information. This evaluation is designed to ensure mixing-layer height monitoring from ceilometer data more reliable.     

Improved Estimation of Errors due to Antenna Geometry in RASS Based on a Radar Wind Profiler

Summary A rigorous theoretical consideration of the parameters of a received signal for a RASS based on a radar wind profiler and operating in the “Bragg”-operation mode is performed. The calculation approach is based on solving the equations analytically for diffractive wave beams and takes into account diffraction effects in the Fresnel approxim ation for both radio and acoustic waves generated by antennas with finite sizes. It is shown that the errors due to the displacement of an acoustic source and horizontal wind are negligible for RASS based on a monostatic radar not only in the far-field but also in the transition zone between the Fresnel diffraction and far-field ranges at the lowest RASS operational heights. Received August 24, 1998 Revised February 25, 1999     

Comparison of Boundary-Layer Profiles and Layer Detection by AMDAR and WTR/RASS at Frankfurt Airport

At Frankfurt airport (EDDF) vertical soundings of the lower atmosphere from two independent sources are available. One of them is a wind and temperature profiler (wind temperature radar and radio acoustic sounding system, WTR/RASS) located at the western end of the main pair of runways. The second source is aircraft meteorological data relay (AMDAR), i.e. measurements operationally collected by approaching and departing aircraft. Together, both offer a rare opportunity to compare the performance of these widely used systems. We use 1 year of continuous data to calculate systematic temperature and wind vector differences between both measurement systems. The differences show a clear season-dependent structure in conjunction with typical inversion heights. Possible causes for this behaviour are discussed. Second, we compare the ability of both systems to identify inversion and wind-shear layers above the airport. AMDAR-detected layers are typically higher than wind profiler detections. The layer base is usually detected with more agreement than the top. The mutual probability of detection of inversions is found to be mostly between 40 and 60%.     

Composite wind and temperature profiles obtained from a complex of in-situ and remote sensing measurement systems for the forcing of a boundary layer model

Summary ?This paper describes the configuration of measurement systems operated continuously at the Meteorological Observatory Lindenberg with the aim of constructing combined profiles of wind and temperature – so-called composite profiles – covering the boundary layer with high temporal and vertical resolution. This is required for the forcing of a micro-α-scale model in order to simulate the atmospheric boundary layer structure over a heterogeneous landscape during the LITFASS-98 experiment. The problems of combining measurements of different remote sensing and in-situ systems are briefly discussed. Although the measuring range of individual remote sensing systems is variable, the height coverage of wind and temperature profile measurements by sodar/RASS and two wind profiler radar/RASS complement each other very well. Using a simple merging procedure composite wind and temperature profiles have been synthesized based on radiosonde, windprofiler/RASS, sodar/RASS and tower measurements. Time-height cross sections of hourly composite profiles show considerably more details of the boundary layer structure than simple radiosonde interpolation due to the higher sampling frequency, higher vertical resolution and increased accuracy at the lower levels. Finally some qualifications of the formulated algorithm are suggested for future application. Received June 18, 2001; revised May 30, 2002; accepted June 6, 2002     

大气廓线综合探测系统及其应用技术

介绍了大气廓线综合探测系统——风廓线仪与RASS雷达的工作原理，并以具体实例来说明这种探测技术在国外高空探测领域中的广泛应用。它可以被用来推算湿度廓线，探测锋的热动力结构与垂直风结构，诊断热带地区行星边界层和降雨云系统。通过对中日科技人员2002年夏季在安徽省肥西县进行的中尺度天气观测试验资料分析，阐述了用风廓线仪和RASS雷达资料反演0．2～2．2km高度范围内湿度廓线的方法。     

Development and Initial Results of a Mobile RASS

Summary A mobile RASS (Radio Acoustic Sounding System), which can be loaded onto a truck along with all the other equipment, including the power supply, was developed for atmospheric temperature measurement. Also, since it is necessary to avoid noise pollution in surrounding areas when conducting observations with the mobile RASS, a new method that allows measurement of the temperature profile up to about 200 m using a single acoustic pulse was devised. We discuss the development of a truck-mounted mobile RASS and the results of the first mobile observation conducted at various locations in the Tokyo area. Received November 3, 1998 Revised June 16, 1999     

The Role of Acoustic Sounding in a High-Technology Era

Summary This paper presents a brief synopsis of past, current and anticipated progress and problems in the use of acoustic remote sensing for basic and applied research of the lower atmosphere. The potential and reality of the sodar for determination of meteorological parameters and turbulence characteristics is discussed. Sodars’ place alongside other ground-based remote sensors, including radar wind profilers, radioacoustic sounding systems (RASS) and lidars, is elucidated. Areas of atmospheric research where Doppler sodar has certain advantages are described such as cost, sensitivity, spatial and temporal resolution and surface layer measurements. The use of sodar in networks of integrated radar/RASS systems designed to supply uninterrupted monitoring of atmospheric parameters for improvements in forecasts of weather and air quality is demonstrated. The special potential role of sodar in education and training of specialists is suggested to aid in developing and using new methods of atmospheric measurements and meeting the requirements of modern environmental science. A number of problems are formulated whose solution would favor further advancement of acoustic remote sensing in integrated systems for remote monitoring of the atmospheric boundary layer. Received November 23, 1998 Revised January 29, 1999     

First Results of Measurements with a Newly-Designed Phased-Array Sodar with RASS

Summary At a special measuring site for boundary-layer studies as well as land-surface processes the Meteorological Observatory Lindenberg of the German Weather Service (DWD) has recently put into operation a newly-desi gned phased-array SODAR/RASS, which has been developed by METEK on behalf of the DWD. This system provides the vertical profiles of the three-di mensional wind vector in the boundary layer on an operational basis and is furthermore suitable for getting information on the profile of virtual temperature up to about 400 m in height based on the addition of RASS components. The following paper describes both the technique of this SODAR/RASS and the various modes of operation as well as the different options in managing the system. First evaluations on the data availability concerning the maximum height coverage will give an impression on the system’s capabilities. Finally, the accuracy of the derived profiles of winds and temperature will be investigated by means of comparisons of the SODAR/RASS data with measurements of a six-sonde tethered-balloon system as well as meteorological data of a 99 m tower in the vicinity of the system. Received November 27, 1998 Revised April 9, 1999     

基于风廓线雷达的湖北梅雨期暴雨中小尺度特征

针对2016年湖北梅雨期3次(“6·19”、“7·5”和“7·19”)暴雨过程,首先对比了汉口站探空数据与汉口、咸宁两个风廓线雷达站水平风速、风向,发现“6·19”和“7·5”过程汉口风廓线雷达站3 km以下水平风速和探空数据较为接近,而3次过程中咸宁风廓线雷达站8 km以下水平风向、风速和汉口站探空数据基本吻合。在此基础上利用风廓线雷达资料并结合常规、加密自动气象站资料,对3次过程中水平风场、平均垂直速度及其变率、水平风速垂直切变、大气折射率结构常数(C■)等进行分析。结果表明：(1)降水开始前西南风速明显增大,中层干冷空气入侵和地面冷池形成的中尺度偏东气流是“6·19”过程50站出现大于等于17.2 m·s^-1大风的主要原因,“7·5”和“7·19”过程西南急流长时间维持及1 km以下的偏东气流则是短时强降水持续时间较长的诱因;(2)梅雨期暴雨期间风廓线雷达观测的水平风速垂直切变、平均垂直速度及其变率随高度变化较小,较强上升运动区域主要集中在4 km高度以下;(3)C■显示强降水发生前大气水汽含量有一增加过程,且整层水汽含量深厚,C■大值区的消失对应降水结束。     

Comparison of wind measurements by means of industrially produced sodar and high-altitude meteorological mast in Obninsk

The real characteristics of the MFAS sodar industrially produced by Scintec AG (Germany) are given. The paper presents a wider range of altitudes as compared with the papers published before as a result of using the meteorological mast with the height of 310 m and longer duration of practically continuous testing embracing different weather conditions in the period from July to November 2008. During the comparison, the 10-min averaging time for the wind speed and direction is used. The comparison of the data of acoustic sounding and contact measurement methods indicates that the sodar provides reliable information on the vertical profiles of average wind speed within the considered altitude range up to 300 m except the cases of heavy rainfalls and low wind speed.     

Determination of boundary-layer parameters using wind profiler/RASS and sodar/RASS in the frame of the LITFASS project

Summary ?Progress in technology as well as signal processing has promoted Wind Profiler Radar (WPR) or sodar with RASS additions to become standard tools in profiling of the atmospheric boundary layer. Apart from these instruments’ basic abilities in profiling mean winds and temperature, this paper will give an emphasis on the profiling of ABL height as well as the turbulent fluxes of sensible heat and momentum both, with respect to methods as well as with respect to realization. The special focus will thereby be laid on the demands for vertical profiling, which were defined within the LITFASS-project of the German Meteorological Service. In the frame of this project, some special measuring campaigns have been performed where remote-sensing systems were used to assess their abilities in profiling ABL parameters. On the base of some case studies from these campaigns comparisons are shown, where results from sodar/RASS and WPR/RASS measurements are compared to measurements from airborne sensor systems and results from numerical models. Regarding turbulent heat fluxes, we found excellent agreement for remotely-sensed flux profiles from WPR/RASS with both, numerical models and airborne in-situ measurements. However, as the inherent errors of the remotely-sensed fluxes are in the order of ± 20 ⋯ 30 W/m² typically, current signal processing does not allow to interpret small-scale vertical structures in the profiles with respect to surface inhomogeneities yet. Received June 16, 2001; revised February 20, 2002; accepted May 30, 2002     

GPS掩星观测的发展及其在气象业务中的应用现状

GPS无线电掩星探测技术已经发展成为一种强有力的、相对经济的观测全球大气的方法.多年对GPS/MET概念卫星、CHAMP和SAC-C等GPS掩星观测的研究表明,GPS掩星观测资料与其他卫星资料相比具有很高的观测精度和垂直分辨率等优点,并且GPS掩星观测不受天气状况的影响,因此对其在天气预报及气候的应用有独特的优势.GP...     

L波段探空高分辨率廓线中近地层信息分析及相关模型

L波段高空气象探测系统的更新换代,提高了大气探测精度,L波段＂秒级＂数据为垂直高分辨率廓线探测信息的获取提供了气象要素再分析的基础平台。为了探讨L波段探空垂直高分辨数据应用的可行性,考虑到用于对比分析的其他观测系统获取＂秒级＂＂高时间密度＂同步观测数据的设备条件,本文重点选用了JICA（中日气象灾害合作研究中心项目）PBL（行星边界层）通量铁塔梯度观测系统来进行对比分析,并构造L波段探空再分析与通量铁塔近地层气象信息相关模型。研究结果表明,L波段探空垂直高分辨率廓线近地层数据能够较好地描述大气边界层内近地层温、湿、压;所建立的温、湿、压模型具有推算PBL铁塔近地层的温、湿、压的可行性。研究结论可为L波段高分辨率垂直廓线再分析平台及其对大气结构描述可行性提供具有应用价值的技术基础。基于L波段高分辨率垂直廓线再分析信息平台的构造,将有助于开发全国L波段探空在数值模式应用方面的潜力,推进探空垂直高分辨信息在数值模式同化系统中新技术的发展。     

Radio wave propagation and acoustic sounding

Radio wave propagation of the decimetric and centimetric waves depends to a large extent on the boundary layer meteorological conditions which give rise to severe fadings, very often due to multipath propagation. Sodar is one of the inexpensive remote sensing techniques which can be employed to probe the boundary layer structure.In the paper a historical perspective has been given of the simultaneously conducted studies on radio waves and sodar at various places. The radio meteorological information needed for propagation studies has been clearly spelt out and conditions of a ray path especially in the presence of a ducting layer have been defined as giving rise to fading or signal enhancement conditions. Finally the potential of the sodar studies to obtain information about the boundary layer phenomena has been stressed, clearly spelling out the use of acoustic sounding in radio wave propagation studies.     

Simultaneous horizontal and vertical acoustic sounding of the atmospheric boundary layer

Some preliminary results from a series of experiments of simultaneous horizontal and vertical acoustic sounding of the atmosphere are described and discussed. The novel horizontal configuration offers some potential for investigating thermal plume motion and characteristics within the boundary layer. It could also be of use in assessing the importance of excess attenuation in quantitative acoustic sounding.     

Vertical velocity field in the convective boundary layer as observed with an acoustic Doppler sodar

The morning development of the daytime convective boundary layer (CBL) during fine weather has been observed with an acoustic Doppler sodar of the C.R.P.E. In particular, the vertical profile of the vertical velocity third-order statistic W* ³ has been obtained. This quantity is a maximum near 0.3z _I where z _I, is the height of the CBL. The histogram of vertical velocity in the CBL shows a relationship between W ³ and the convective velocity W _* and is useful for convective plume determination.     

新疆西南部一次局地对流性暴雨成因分析

利用常规地面和探空气象资料、NCEP逐6h1°×1°的再分析资料和(CINRAD-CC)多普勒雷达探测资料,对2012年7月19日新疆阿图什罕见的短时对流性暴雨形成原因进行了诊断分析。结果表明:此次天气是在南疆低涡有利的环流背景下、低层中尺度低涡促进上升运动及触发不稳定能量释放产生的;冷空气的入侵是造成对流扰动发展的重要原因,同时地面小尺度系统对触发不稳定能量释放也有一定的作用;涡散场的配置、垂直速度、低层偏东急流和强不稳定能量满足了对流发生的基本条件,而较强的垂直风切变则使风暴明显增强;从喀什探空订正图来看,修正后的探空资料中各要素对开展强对流潜势预报有很好的指示意义,有待进一步总结验证;对多普勒雷达资料的分析表明,此次强降水具有强回波、强的垂直风切变、大的垂直液态水含量和较高回波顶高等,与强对流天气的发生发展及落区有较好的对应关系。     

基于往返式平漂探空的FY-3D卫星反演温度检验

往返式平漂探空观测（以下简称平漂探空）可实现对流层至平流层低层大气温度廓线垂直探测以及平流层低层内持续4 h的水平温度分布探测。该文介绍利用平漂探空试验数据对风云3号气象卫星D星（FY-3D）反演温度数据的检验评估算法,基于该算法和2021年3—9月长江中下游平漂探空试验数据完成对卫星反演大气温度数据的检验。结果显示:FY-3D卫星反演的温度数据准确度总体较高,与平漂探空上升段数据平均绝对偏差约为1.34℃,与下降段数据平均绝对偏差约为1.93℃;卫星反演的100 hPa以上和850 hPa以下温度误差分别偏大0.59℃和0.33℃;卫星反演平流层温度准确度低于温度廓线,平均绝对偏差约为3.92℃;与平漂探空数据相比,卫星大气温度廓线分辨率较低、趋势较平滑,无法显示大气温度垂直分布和平流层温度水平分布的细节特征。