共查询到20条相似文献，搜索用时 15 毫秒
1.
Simultaneous observations were made of the Marine Boundary Layer at Tarapur, a site near Bombay on the sea coast, by acoustic sounder and instrumented tower. The meteorological tower was used to sense wind and temperature at various levels up to a height of 120 m while the acoustic sounder was used to examine the thermal structure of the boundary layer up to a height of 700 m. Data recorded for the year 1982 have been analysed.Analysis of the data shows that while the normal structures of thermal echoes and shear echoes represent the mixing depth of the atmospheric boundary layer, the often observed elevated layers are due to sea breeze reversals with their base giving a measure of the depth of the sea-breeze circulation during the day. A sea breeze has been detected during both spring (March to May) and autumn (October to December) months. The onset times are around 1000 hr during spring months and around noon during the autumn period, the height of development being respectively up to 500 and 350 m. The capability of the sodar to detect the base and thickness of the sea breeze, is clearly revealed. 相似文献
2.
S. K. Aggarwal S. P. Singal Ramesh K. Kapoor B. B. Adiga 《Boundary-Layer Meteorology》1980,18(4):361-371
Simultaneous observations were made by an acoustic sounder and on a meteorological tower during the month of May 1978 at the Atomic Power Station Tarapur. The probing range of the acoustic sounder was 700 m. The meteorological tower could sense wind and temperature at various levels up to a height of 120 m.The site being close to the sea shore, the thermal environment of the lower atmosphere is controlled mostly by land and sea breeze circulations. Thermal convective structures were seen during the daytime and also at night. The frequency of plume formation and the height of the plumes were, however, low during the night. The convective boundary layer in the daytime ranged from 400–500 m while at night it was mostly under 200 m. The observation of thermals at night is explained by the presence of a naturally stable marine layer above 30 m at this site. In the morning hours, winds suddenly change their direction allowing advection of a land breeze which is responsible for the formation of surface-based shear echoes to a height of 200 m during the transition period and for the subsequent development of an elevated layer due to mixing of two different air masses. A marine layer was also seen over Tarapur for a few days during the early evening and night hours. Its height was mostly around 400 m. It may indicate the presence of a subsidence inversion at Tarapur. The need for collection of supporting meteorological data to a height of 500 m by tethered balloon or some other suitable in-situ technique is stressed. 相似文献
3.
P Thomas 《Atmospheric Research》1986,20(2-4)
Two different Doppler acoustic sounders have been operated at the Kernforschungszentrum Karlsruhe (KfK) since 1982. It has been investigated whether meteorological data from these sounders can be used for dispersion modeling and monitoring in the environment of pollutant-emitting plants. Data from the sounders and from a 200 m high meteorological tower have been sampled continuously for intercomparison.Two schemes of stability classification are presented. They are based on 30-min mean values of the following meteorological data measured by the acoustic sounders: (a) standard deviation σw of the vertical wind speed and horizontal wind speed u, at a height of 100 m; and (b) standard deviation σφ of the vertical wind direction at a height of 100 m and vertical profile of the backscattered amplitude Aw.The class limits applied in these schemes are determined by “statistical equivalence” with a standard classification scheme. This standard scheme is based on σφ, measured by a vector vane at the 100 m level of the tower. Statistical equivalence in this context means that the frequency distributions of the classes are approximately equal at the same site and during the same period.The reliability of these schemes is investigated and compared to the standard scheme by correlation analysis. Finally, the schemes are compared with other commonly applied classification methods. 相似文献
4.
Gravity waves associated with stably stratified layers were observed in the planetary boundary layer at two locations in France. Using an array of three monostatic Doppler acoustic sounders, the wave speeds and directions were found. A quantitative study of the waves has been performed to determine their physical characteristics. Based on their dynamics, a classification into three types was possible. Most were found to be trapped beneath a critical level. 相似文献
5.
J. H. Richter D. R. Jensen R. A. Pappert V. R. Noonkester 《Boundary-Layer Meteorology》1973,4(1-4):179-199
Simultaneous lidar and FM-CW (frequency modulated-continuous wave) radar observations are presented and both common and different features observed with the two remote sensors are described. Among the common features are Kelvin-Helmholtz (K-H) waves and turbulent structures. The potential of the FM-CW radar as a meteorological tool for aiding fog dissipation forecasts is illustrated. The data also indicate that the radar often detects echoes from height regions which coincide with cloud tops. A new FM-CW radar sounder is described which incorporates scanning capability and which is fully mobile. Examples of recent observations are presented illustrating the capabilities of this second generation radar sounder.Future applications of the FM-CW radar sounder, such as investigations of the exact nature of the mechanism responsible for the radar returns, require accurate calibration of the radar sounder. It is shown that resolution and sensitivity of a linear frequency-modulated FM-CW radar depend on the time delay of the signal. Range dependency on resolution and sensitivity is calculated for various periodic and stochastic perturbations in a linear modulation and good agreement is found between calculated and measured values. 相似文献
6.
B. R. Bean A. S. Frisch L. G. McAllister J. R. Pollard 《Boundary-Layer Meteorology》1973,4(1-4):449-474
Clear-air plume and wave-like structures are revealed in the atmospheric boundary layer by combined acoustic remote sensing and meteorological tower measurements. The magnitude of turbulent production and dissipation plus properties of velocity and temperature spectra determined from the tower measurements are well correlated with phenomena indicated by the acoustic sounder. Interpretation of either set of records is greatly enhanced by the other. For example, the onset of a sudden burst of turbulent production from the tower measurements may correspond to plume passage or breaking of stable waves recorded by the acoustic echo sounder. 相似文献
7.
Estimation of abl Parameters Using the Vertical Velocity Measurements of an Acoustic Sounder 总被引：2，自引：0，他引：2
J. A. Kalogiros C. G. Helmis D. N. Asimakopoulos P. G. Papageorgas 《Boundary-Layer Meteorology》1999,91(3):413-449
The friction velocity, the surface heat flux and the height of the Atmospheric Boundary Layer (ABL) are important parameters. In this work, vertical velocity variance (
w
2
) and wind velocity structure parameter (C
v
2
) profiles estimated by acoustic sounder measurements are used, along with similarity relations, to estimate these parameters in the unstable Atmospheric Boundary Layer and the friction velocity in the stable one. The data were collected by two acoustic sounders with different height range and resolution under various atmospheric conditions (stability) and at two experimental sites in different terrain. The C
v
2
profiles are estimated using gate difference of the vertical velocity measurements and the assumption of local isotropy. The vertical velocity data are corrected for the significant effects of noisy measurements and sampling volume averaging on the
w
2
and C
v
2
estimations using original techniques that are presented in this work. The results of the similarity method using acoustic sounder data are compared against estimates of the corresponding atmospheric parameters obtained from direct measurements. The comparison confirms the ability of the method to provide reasonably accurate estimates of these parameters especially in the middle of the day. 相似文献
8.
A radar equation which can be applied to any bistatic acoustic sounder is derived. The equation reduces to the expression normally used for the special case of the monostatic sounder. Numerical results using this equation are given for specific acoustic sounders, including the relative contributions to the scattering from the temperature and velocity parameters (C
T
2 and C
V
2), the effect of wind speed on the scattered intensity and the measurement of horizontal wind velocity.Now with the Department of Electrical and Electronic Engineering, Portsmouth Polytechnic, Anglesea Road, Portsmouth PO1 3DJ. 相似文献
9.
An acoustic echo sounder situated in downtown Toronto has been used to detect convective plumes in the planetary boundary layer and to measure, by means of the Doppler effect, the vertical air motions associated with them. The plumes observed were the order of 390 m in horizontal extent, were detectable to a height of about 400 m, and were characterized by peak upward velocities in excess of 1 m s?1. The sounder measurements are shown to be consistent with surface meteorological parameters, and suggest that free convection over an urban area of considerable surface roughness and non‐uniformity is not greatly different from that over uniform land surfaces or water. 相似文献
10.
Tak Kee Cheung 《Boundary-Layer Meteorology》1991,57(3):251-274
Events in the stably stratified lower atmospheric boundary layer within the first several hundreds of meters at Barrow, Alaska were recorded from 27 March to 5 April 1990 using an acoustic sounder (sodar), a tethered balloon, radiosondes, and an instrumented meteorological tower. These events include ground-based and low-level inversion layers, gravity waves, breaking waves, and multiple-layer structures. Even though these events are commonly found in a stable boundary layer, it is perhaps surprising to find them in such a slowly changing environment and over a terrain that is essentially devoid of immediate orographic influence.Visiting Scientist at Wave Propagation Laboratory, NOAA/ERL 325 Broadway, Boulder, CO, 80303, U.S.A. 相似文献
11.
Acoustic sounders have now been used extensively in a series of noctural drainage flow experiments carried out by the U.S. Department of Energy's Atmospheric Studies in Complex Terrain (ASCOT) program. Doppler acoustic sounders, located in three different valleys during the sequence of experiments, reveal drainage-wind profiles that depend strongly on the ambient meteorological conditions and the elevation of each observing site relative to surrounding terrain. In elevated sites that drain easily, Doppler-sounder derived wind profiles show a simply-structured flow; in lower lying areas, subject to topographic constriction and cold-air pooling, and where Archimedean forces are comparable to those due to synoptic and mesoscale pressure gradients, the wind profiles show considerable vertical and temporal variation. In particular, in the Geysers area of northern California, the seabreeze and the depth of the Pacific Coast marine inversion affect not only the initiation of drainage winds but also their subsequent evolution. 相似文献
12.
Zhenglong LI Jun LI Pei WANG Agnes LIM Jinlong LI Timothy J.SCHMIT Robert ATLAS Sid-Ahmed BOUKABARA Ross N.HOFFMAN 《大气科学进展》2018,35(10):1217-1230
Accurate atmospheric temperature and moisture information with high temporal/spatial resolutions are two of the key parameters needed in regional numerical weather prediction(NWP) models to reliably predict high-impact weather events such as local severe storms(LSSs). High spectral resolution or hyperspectral infrared(HIR) sounders from geostationary orbit(GEO) provide an unprecedented source of near time-continuous, three-dimensional information on the dynamic and thermodynamic atmospheric fields—an important benefit for nowcasting and NWP-based forecasting. In order to demonstrate the value of GEO HIR sounder radiances on LSS forecasts, a quick regional OSSE(Observing System Simulation Experiment)framework has been developed, including high-resolution nature run generation, synthetic observation simulation and validation, and impact study on LSS forecasts. Results show that, on top of the existing LEO(low earth orbit) sounders, a GEO HIR sounder may provide value-added impact [a reduction of 3.56% in normalized root-mean-square difference(RMSD)] on LSS forecasts due to large spatial coverage and high temporal resolution, even though the data are assimilated every 6 h with a thinning of 60 km. Additionally, more frequent assimilations and smaller thinning distances allow more observations to be assimilated, and may further increase the positive impact from a GEO HIR sounder. On the other hand, with denser and more frequent observations assimilated, it becomes more difficult to handle the spatial error correlation in observations and gravity waves due to the limitations of current assimilation and forecast systems(such as a static background error covariance). The peak reduction of 4.6% in normalized RMSD is found when observations are assimilated every 3 h with a thinning distance of 30 km. 相似文献
13.
Operation of a monostatic acoustic sounder on the campus of The University of Calgary for the period March to September, 1976, has provided data on the atmospheric boundary layer over Calgary. The formation and dissipation of the nocturnal temperature inversion layer leaves a clear signature in the sounder records. A trend is discerned in which the nocturnal layer tends to form at sunset, whereas convective instability is established some 2–3 hours after sunrise. Comparison of sounder records with an extensive set of radiosonde temperature profiles has shown that the height of the inversion layer can be determined reliably when a single, dark, ground-based return is visible on the sounder charts. On many occasions, however, the sounder detects multiple structures in the atmosphere. In these cases, it is difficult to establish a systematic correspondence of the turbulent structure as observed in the sounder records with the temperature profile as observed by the radiosonde. 相似文献
14.
P. A. Mandics 《Boundary-Layer Meteorology》1973,4(1-4):311-322
The index of refraction and its short-term variations have been measured on a 152-m meteorological tower at three fixed levels and on a moveable platform. Analysis of the data reveals that the time rates of production and dissipation of refractivity fluctuations are approximately in balance under a variety of meteorological conditions, and that changes in the rate of dissipation usually coincide with comparable changes in the rate of production. Under reasonably stationary conditions, terms corresponding to the rate of change and vertical diffusion of refractivity variance are found to be negligible. Power spectral densities of the variations increase when the rate of generation (and dissipation) increase, and conversely. Comparison of the results with simultaneous acoustic sounder returns provides a valuable insight into the mechanisms responsible for changes in the rates of production and dissipation. 相似文献
15.
The planetary boundary layer (PBL) over the Indian Antarctic station, Maitri (70.7° S; 11.7° E; 120 m asl) has been studied using a monostatic acoustic sounder. Acoustic sounder records reveal that the Antarctic PBL remains stably stratified throughout the year except for some periods in the peak summer months. The summertime PBL exhibits a diurnal variation with ground-based inversions developing at night and the convective plumes occurring during the peak sunlight hours. The cyclonic inflow of warm oceanic air towards the continent's interior from the coast helps in the development of the elevated layers and the Kelvin-Helmholtz waves observed on the sodar records. 相似文献
16.
基于2014—2016年南京市常规气象逐时观测数据、逐日用电量和逐时用电负荷数据, 分析南京市用电量变化及其与气象因子的关系。结果表明: 南京市用电量7—8月、12月至翌年1月为两个峰值, 4月和10月为两个谷值, 年变化明显。四季均呈现显著“周末效应”。用电负荷一天内有两个峰值, 分别出现在10时和20时; 两个谷值, 一个谷值冬夏季在04时, 另一谷值冬季在14时, 夏季在18时。南京市用电量与气象条件的变化密切相关, 气象因子与用电量的关系在不同月份有所不同, 如夏(秋、冬)季气温日较差越大(小), 用电量越大; 7月、8月(10月至翌年3月)气温越高(低), 用电量越大; 冬季用电量受气象要素的影响程度总体低于夏季。冬季用电量主要受气温制约; 夏季用电量受气象要素的影响更为复杂, 除了气温, 还需综合考虑水汽、日照等因子。利用逐步回归法, 建立冬、夏季逐月日用电量气象预测方程, 方程中入选气象因子的存在明显的月际差异。不同月份分别针对性地考量入选气象因子的预报值, 做出用电量预估, 可为电力调度提供参考。 相似文献
17.
南阳市土壤湿度与气候变化的关系分析 总被引：1，自引：0，他引：1
根据19812005年的气象观测资料和土壤湿度测定资料,利用统计学方法,分析了南阳市土壤湿度变化规律及与温度、降水的关系,结果表明:土壤湿度无论是年均值或最小值都呈明显下降趋势,年平均相对湿度下降约0.4%;浅层湿度变化幅度小,深层变化幅度大.影响土壤湿度的气象因子中,气温与浅层土壤湿度呈明显的负相关,降水量与深层土壤湿度呈明显正相关;各季土壤湿度与气温和降水量的二元回归方程都通过了F检验,其中春秋冬季通过0.01的显著性检验,夏季通过0.05的显著性检验. 相似文献
18.
西安市冬季采暖气象条件分析和预报方法初探 总被引：6，自引：2，他引：6
对西安市冬季采暖气象条件和预报方法进行了研究。根据国家采暖规范结合西安冬季采暖的实际，首先对西安1951年7月到2003年6月历年的逐日气象资料进行了详尽的分析，比较了国家采暖日期相关规范和规定中的3种不同的统计方法，确定了符合西安特点的采暖初终日。充分利用T213数值预报产品，对2002年和2003年两个冬半年的逐日850hPa和500hPa各时次各类气象要素及与之对应的西安各时次实况的气温作了相关分析，建立了回归方程，提出了采暖期及其逐日气温预报。 相似文献
19.
20.
Between November 15 and 30, 1985, an international mesoscale transport experiment was performed on the Swiss Plain. Seven meteorological groups from Denmark, Germany, Italy and Switzerland measured diffusion properties of near neutral planetary boundary layers during six completely overcast days: four Bise (north-east wind) situations, one transitional situation and one west-wind situation. Diffusion was measured using SF6 as tracer, which was released at the meteotower of the Gösgen nuclear power plant at 6 m above ground level. One hundred automatic samplers plus a mobile gas chromatograph were used to measure the concentration fields at distances up to 90 km downwind. Meteorological parameters were observed using radar-tracked constant-level balloons, tethered balloon soundings, sonic anemometers, an acoustic sounder and several meteorological ground stations, including a 110 m mast. All data were collected on a magnetic tape with free access to interested persons.The aim of the experiments was to obtain knowledge about the general nature of the turbulence, advection and atmospheric dispersion during neutral weak-wind situations over complex terrain. The collected data set will be useful for testing mesoscale transport and diffusion models. The results clearly show the channelling effect of the Jura mountains and the hilly prealpine region. An interesting result is that the SF6 plumes showed intensive horizontal spread but only limited diffusion in the vertical direction. 相似文献