共查询到20条相似文献,搜索用时 15 毫秒
1.
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 相似文献
2.
Recent investigations in complex terrain have found that remote sensing instrumentation commonly finds mean wind-speed differences
when compared to cup anemometery. In many cases the difference is found to be an underestimation and varies from 2 to 9% depending
on topology. We describe these differences in a theoretical sense for a five-beam sodar. An investigation is conducted on
a New Zealand ridge with a five-beam sodar and three computational models, consisting of a potential flow model and two computational
fluid dynamical simulations, OpenFOAM and the industry standard software WindSim. All models predict the difference to within
0.1–2.5%. A comparative assessment is made and it is found that, given the computing overheads, the potential flow model provides
a good compromise in the prediction of mean wind-speed difference. 相似文献
3.
4.
J. Keder 《Meteorology and Atmospheric Physics》1999,71(1-2):133-138
Summary A REMTECH PA2 Doppler Sodar is operated regularly at the Czech Hydrometeorological Institute (CHMI) observatory in Prague,
collocated with a routine rawinsonde sounding system. The Air Pollution Control Division of CHMI utilises the sodar data in
air pollution studies and as an information support for the smog warning system operated in Prague. Besides of the basic software
for echo strength and wind profile evaluation, optional routines for deriving parameters such as inversion and mixing height,
stability class etc. were delivered by the sodar manufacturer. Based on a sufficiently large data set (more than one year)
of synchronous sodar and rawinsonde measurements, an analysis and comparison of inversion and mixing heights provided by both
sounding systems have been accomplished in order to evaluate the correctness and accuracy of sodar estimates of these parameters.
In contrast to the wind speed and wind direction data, for which a satisfactory agreement with other kind of measurements
has been reported by many studies, the results for inversion and mixing height detection were totally disappointing. A direct
applicability of inversion height and mixing height data provided by the REMTECH’s automatic routines in air pollution studies
or smog warning systems is quite problematical with the present “state of the art”.
Received November 3, 1998 Revised April 20, 1999 相似文献
5.
Sonja Weinbrecht Siegfried Raasch Astrid Ziemann Klaus Arnold Armin Raabe 《Boundary-Layer Meteorology》2004,111(3):441-465
An attempt is made to compare results oflarge-eddy simulation (LES) in a convective boundarylayer using the model PALM with experimental data obtained from acoustic travel time tomography.This method provides two-dimensional data arrays, which are considered as more suitable forLES-validation than classical local orline-integrated measurements, because the tomographic data are area- or volume-averaged.For a quantitative comparison with experimental data in general, some prerequisites have to be considered: First of all, the initial and boundary conditions of the LES model have to be provided correctly by the experiment. Considering measurement errors, a sensitivity study was performed to investigate the influence of inaccurate initial and boundary conditions on the simulation results.This showed that for determining some boundary conditions, such as the surface temperature and the roughness length, high measurement accuracies are necessary, which are difficult to reach or which at least require considerable extra measurement efforts.The initial and boundary conditions provided by the Lindenberg experiment in 1999 turned out to be of insufficient accuracy to allow quantitative comparisons.However, a qualitative comparison was performed instead to investigate if the acoustic tomography method is a proper method for comparisons with LES models in general.It showed a good qualitative agreement with some quantitative differences. These differences can partly be explained by the sensitivity of the LES to initial and boundary conditions and by the limitations of the acoustic tomography. 相似文献
6.
Xiaoqiong ZHEN Shuqing MA Hongbin CHEN Guorong WANG Xiaoping XU Siteng LI 《大气科学进展》2022,39(3):386-402
A novel weather radar system with distributed phased-array front-ends was developed. The specifications and preliminary data synthesis of this system are presented, which comprises one back-end and three or more front-ends. Each front-end, which utilizes a phased-array digital beamforming technology, sequentially transmits four 22.5°-width beams to cover the 0°–90° elevational scan within about 0.05 s. The azimuthal detection is completed by one mechanical scan of0°–360° azimuths within about 12 s volume-scan update time. In the case of three front-ends, they are deployed according to an acute triangle to form a fine detection area(FDA). Because of the triangular deployment of multiple phased-array front-ends and a unique synchronized azimuthal scanning(SAS) rule, this new radar system is named Array Weather Radar(AWR). The back-end controls the front-ends to scan strictly in accordance with the SAS rule that assures the data time differences(DTD) among the three front-ends are less than 2 s for the same detection point in the FDA. The SAS can maintain DTD < 2 s for an expanded seven-front-end AWR. With the smallest DTD, gridded wind fields are derived from AWR data, by sampling of the interpolated grid, onto a rectangular grid of 100 m ×100 m ×100 m at a 12 s temporal resolution in the FDA. The first X-band single-polarized three-front-end AWR was deployed in field experiments in 2018 at Huanghua International Airport, China. Having completed the data synthesis and processing, the preliminary observation results of the first AWR are described herein. 相似文献
7.
Fifteen hours of Sodar echoes, collected during the 4th Environmental CEC Campaign at Turbigo, Italy, in September 1979, have been analyzed. We discuss the vertical profiles and the time evolution of the second and third statistical moments of the vertical component of wind velocity, measured at a rate of one height-profile every 6 s for a height range of 1000 m and a vertical resolution of 29 m. We also analyze the power spectra of the vertical velocity. 相似文献
8.
Stefan Emeis Klaus Sch?fer Christoph Münkel Roman Friedl Peter Suppan 《Boundary-Layer Meteorology》2012,143(1):25-35
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. 相似文献
9.
Stefania Argentini Giangiuseppe Mastrantonio Igor Petenko Ilaria Pietroni Angelo Viola 《Boundary-Layer Meteorology》2012,143(1):177-188
Measurements in the atmospheric surface layer are generally made with point sensors located in the first few tens of metres.
In most cases, however, these measurements are not representative of the whole surface layer. Standard Doppler sodars allow
a continuous display of the turbulent thermal structure and wind profiles in the boundary layer up to 1000 m, with a few points,
if any, in the surface layer. To overcome these limitations a new sodar configuration is proposed that allows for a higher
resolution in the surface layer. Because of its capabilities (echo recording starting at 2 m, echo intensity vertical resolution
of approximately 2 m, temporal resolution of 1 s) this sodar is called the surface-layer mini-sodar (SLM-sodar). Features
and capabilities of the SLM-sodar are described and compared with the sodar. The comparison of the thermal vertical structure
given by the SLM-sodar and the sodar provides evidence that, in most cases, the surface layer presents a level of complexity
comparable to that of the entire boundary layer. Considering its high vertical resolution, the SLM-sodar is a promising system
for the study of the nocturnal surface layer. The nocturnal SLM-sodar measurements have shown that, depending on wind speed,
the structure of the surface layer may change substantially within a short time period. At night, when the wind speed is greater
than 3 m s−1, mechanical mixing destroys the wavy structure present in the nocturnal layer. Sonic anemometer measurements have shown that,
in such cases, also the sensible heat flux varies with height, reaching a peak in correspondence with the wind speed peak.
Under these conditions the assumption of horizontal homogeneity of the surface layer and the choice of the averaging time
need to be carefully treated. 相似文献
10.
Christoph Thomas Jens-Christopher Mayer Franz X. Meixner Thomas Foken 《Boundary-Layer Meteorology》2006,119(3):563-587
This study applies acoustic sounding to observe coherent structures in the roughness sublayer (RSL) above tall vegetated surfaces. Data were collected on 22 days during two separate field experiments in summer 2003. A quality control scheme was developed to ensure high data quality of the collected time series. The data analysis was done using both discrete and continuous wavelet transform. The flow in the RSL was found to be a superposition of dynamic Kelvin–Helmholtz instabilities and convective mixing. The characteristic time scales for coherent structures resulting from the dynamic instabilities were observed to be approximately 20–30 s while thermal eddies have much larger time scales of 190–210 s. The degree of vertical coherency in the RSL increases with the flow evolving from neutral to near-convective conditions. This increase in the degree of organisation is attributed to the evolution of attached thermal eddies. The coherent structures resulting from instabilities were found to be present throughout the RSL but do not contribute to the increased vertical coherency. An alternative conceptual approach for the definition of the RSL is proposed, which yields its maximum vertical extent to five times the canopy height. 相似文献
11.
We evaluate the statistical properties of low-level jets (LLJs) observed by means of a network of Doppler sodars in the Moscow
region, Russia. Continuous long-term measurements of the echo-signal intensity and wind-velocity profiles were carried out
in July 2005 and in 2008–2010 synchronously in the centre of Moscow and at a rural site. The summertime nocturnal LLJs have
a very clear diurnal cycle and exhibit features predicted by the Blackadar mechanism. In contrast, the long-lasting wintertime
jets do not have any clear diurnal variability. The urban environment strongly influences LLJs in both seasons: above the
city LLJs are higher, weaker and observed more rarely than at the rural site. In very cold periods (air temperature below
−8°C) no LLJs were observed over the city, instead convection emerged in the urban boundary layer. The results are based on
observations made in July 2005, January and December 2009, and January 2011. 相似文献
12.
I. V. Petenko 《Meteorology and Atmospheric Physics》1999,71(1-2):69-79
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 相似文献
13.
A Two-Moment Bulk Microphysics Coupled with a Mesoscale Model WRF: Model Description and First Results 总被引:1,自引:0,他引:1
The Chinese Academy of Meteorological Sciences (CAMS) two-moment bulk microphysics scheme was adopted in this study to investigate the representation of cloud and precipitation processes under different environmental conditions.The scheme predicts the mixing ratio of water vapor as well as the mixing ratios and number concentrations of cloud droplets,rain,ice,snow,and graupel.A new parameterization approach to simulate heterogeneous droplet activation was developed in this scheme.Furthermore,the improved CAMS scheme was coupled with the Weather Research and Forecasting model (WRF v3.1),which made it possible to simulate the microphysics of clouds and precipitation as well as the cloud-aerosol interactions in selected atmospheric condition.The rain event occurring on 27-28 December 2008 in eastern China was simulated using the CAMS scheme and three sophisticated microphysics schemes in the WRF model.Results showed that the simulated 36-h accumulated precipitations were generally agreed with observation data,and the CAMS scheme performed well in the southern area of the nested domain.The radar reflectivity,the averaged precipitation intensity,and the hydrometeor mixing ratios simulated by the CAMS scheme were generally consistent with those from other microphysics schemes.The hydrometeor number concentrations simulated by the CAMS scheme were also close to the experiential values in stratus clouds.The model results suggest that the CAMS scheme performs reasonably well in describing the microphysics of clouds and precipitation in the mesoscale WRF model. 相似文献
14.
大孔径闪烁仪是近年兴起的测量大尺度(500 m~10 km)地表通量的仪器。北京师范大学等单位分别于2002年、2004年在北京昌平小汤山开展了大孔径闪烁仪短期观测实验, 2006年6月又在北京密云建立了长期观测站。利用这些数据, 对大孔径闪烁仪观测数据进行处理与分析, 结果表明:闪烁仪光径高度和风速是影响观测显热通量的关键因子。当地表粗糙元的高度变化相对于光径高度不可忽略时, 零平面位移需要精确确定。波文比在湿润地表需要准确确定, 而气温、气压和动力学粗糙度则为不敏感因子。计算中所需的大气稳定度可用理查孙数判断, 也可借助日出日落时间或净辐射观测值确定。稳定条件下的普适函数目前无统一表达式, 可采用仪器说明书推荐的函数。通过几个站点闪烁仪观测显热通量与涡动相关仪测量值的比较表明:大孔径闪烁仪在均匀和非均匀地表都能得到合理的显热通量观测值。 相似文献
15.
The strong destructive winds during tornadoes can greatly threaten human life and destroy property. The increasing availability of visual and remote observations, especially by Doppler weather radars, is of great value in understanding tornado formation and issuing warnings to the public. In this study, we present the first documented tornado over water detected by a state-of-the-art dual-polarization phased-array radar (dual-PAR) in China. In contrast to new-generation weather radars, the dual-PAR shows great advantages in tornado detection for its high spatial resolution, reliable polarimetric variables, and rapid-scan strategy. The polarimetric signature of copolar cross-correlation coefficient with anomalously low magnitude appears to be effective for verifying a tornado and thus is helpful for issuing tornado warnings. The Guangdong Meteorological Service has been developing an experimental X-band dual-PAR network in the Pearl River Delta with the goal of deploying at least 40 advanced dual-PARs and other dual-polarization weather radars before 2035. This network is the first quasi-operational X-band dual-PAR network with unprecedented high coverage in the globe. With such high-performance close-range PARs, efficient operational nowcasting and warning services for small-scale, rapidly evolving, and damaging weather (e.g., tornadoes, localized heavy rainfall, microbursts, and hail) can be expected. 相似文献
16.
J. Winkler P. Blank K. Glaser J. A. G. Gomes M. Habram C. Jambert W. Jaeschke S. Konrad R. Kurtenbach P. Lenschow J. C. Lörzer P. E. Perros M. Pesch H. J. Prümke B. Rappenglück Th. Schmitz F. Slemr A. Volz-Thomas B. Wickert 《Journal of Atmospheric Chemistry》2002,42(1):465-492
During the Berlin Ozone Experiment BERLIOZ in July–August 1998 quasi-continuous measurements ofC2–C12 nonmethane hydrocarbons (NMHCs) were carried out at 10 sites in and around the city of Berlin using on-line gas-chromatographic systems (GCs) with a temporal resolution of 20–120 minutes. Additional airborne NMHCmeasurements were made using canister sampling on three aircraft and an on-line GC system on a fourth aircraft. The ground based data are analyzed to characterize the different sites and to identify the influence of emissions from Berlin on its surroundings. Benzene mixing ratios at the 4 rural sites were rather low (<0.5 ppbv). Berlin (and the surrounding highway ring) was identified as the main source of anthropogenic NMHCs at Eichstädt and Blossin, whilst other sources were important at the furthermost site Menz. The median toluene/benzene concentration ratio in Berlin was 2.3 ppbv/ppbv, agreeing well with measurements in other German cities. As expected, the ratios at the background sites decreased with increasing distance to Berlin and were usually around one or below. On 20 and 21 July, the three northwesterly sites were situated downwind of Berlin and thus were influenced by its emissions. Considering the distance between the sites and the windspeed, the city plume was observed at reasonable time scales, showing decreasing toluene/benzene ratios of 2.3, 1.6 and 1.3 with increasing distance from Berlin. Isoprene was the only biogenic NMHC measured at BERLIOZ. It was themost abundant compound at the background sites on the hotter days, dominating the local NMHC reactivity with averaged contributions to the total OH loss rate of 51% and 70% at Pabstthum and Blossin, respectively. Emissionratios (relative to CO and to the sum of analysed NMHCs) were derived from airborne measurements. The comparison with an emission inventory suggests traffic-related emissions to be the predominating source of the considered hydrocarbon species. Problems were identified with the emission inventory for propane, ethene and pentanes. 相似文献
17.
Dongxu YANG Janne HAKKARAINEN Yi LIU Iolanda IALONGO Zhaonan CAI Johanna TAMMINEN 《大气科学进展》2023,40(1):1-1
China’s first carbon dioxide(CO2) measurement satellite mission, TanSat, was launched in December 2016. This paper introduces the first attempt to detect anthropogenic CO2 emission signatures using CO2 observations from TanSat and NO2 measurements from the TROPOspheric Monitoring Instrument(TROPOMI) onboard the Copernicus Sentinel-5 Precursor(S5P) satellite. We focus our analysis on two selected cases in Tangshan, China and Tokyo, Japan.We found that t... 相似文献
18.
Evolution of some boundary-layer parameters mainly estimated with a Doppler Sodar during perturbed meteorological situation is examined during the Mesogers 84 experiment. A case study of the sodar detection of frontal evolution and the prevailing wind field is presented in conjunction with the surface network measurements. The frontal boundary-layer signature has been observed to be structured into two strong shear layers in the ABL. At the surface, several modifications of the boundary-layer parameters are noticed well in advance of the frontal onset. 相似文献
19.
Measurements of natural ice nuclei were made in winter continental airmasses with a continuous flow thermal gradient diffusion chamber (described in a separate paper). Over the range of temperatures −7°C to −20°C, the concentration of ice nuclei was closely related to ice supersaturation (SSi) for humidities both below and above water saturation. Measurements below water saturation were interpreted as deposition nuclei with average concentrations (per liter) approximately 0.32 SSi(%)0.81. Measurements were made up to 5% above water saturation and activated both deposition and condensation-freezing nuclei. The average concentration of condensation-freezing nuclei was 0.25 e−0.15 T(°C). Sample residence time in the chamber was probably too small to detect contact nuclei, unless the nucleating aerosols are extremely small. There was large variability in nucleus concentrations, as much as two orders of magnitude at −15°C. Comparisons are made between these ice nuclei measurements and aircraft observations of ice crystal concentrations in winter orographic clouds. 相似文献
20.
The European Centre for Medium-Range Weather Forecasts Re-Analysis Interim
(ERA-Interim) meteorology and measurements from the Microwave Limb Sounder,
High Resolution Dynamics Limb Sounder, and Ozone Monitoring Instrument
onboard the Earth Observing System Aura satellite were applied to analyze
the dynamical and chemical features of a cutoff low (COL) event over
northeast China in early July 2007. The results showed the polar
stratospheric origin of an upper-level warm-core cyclone at 100--300 hPa,
associated with a funnel-shaped tropopause intruding into the
mid-troposphere just above the COL center. The impacts of the stratospheric
intrusion on both column ozone and ozone profiles were investigated using
satellite measurements. When the intensity of the COL peaked on 10 July
2007, the total column ozone (TCO) increase reached a maximum (40--70 DU).
This could be dynamically attributed to both the descent of the tropopause
(~75%) and the downward transport of stratospheric ozone across the
tropopause (~25%). Analysis of the tropospheric ozone profiles
provided evidence for irreversible transport/mixing of ozone-rich
stratospheric air across the tropopause near the upper-level front region
ahead of the COL center. This ozone intrusion underwent downstream transport
by the upper tropospheric winds, leading to further increase in TCO by
12--16 DU over broad regions extending from east China toward the northern
Japan Sea via South Korea. Meteorological analysis also showed the
precedence of the stratospheric intrusion ahead of the development of
cyclones in the middle and lower troposphere. 相似文献