共查询到20条相似文献，搜索用时 31 毫秒
1.
Profile data from simultaneous sodar and tethered balloon measurements have been analyzed with respect to the complex structure of the atmospheric boundary layer in the Upper Rhine Valley. Special attention was focused on ozone concentration profiles measured with a novel lightweight ozone sensor at the balloon. In general, good agreement was found between the signature of the ozone concentration profiles and special features of the backscattered sound intensity profiles. This allows reliable estimation of the mixing height from the sodar data even in a complex stable ABL, except for very shallow mixing layers (below about 75 m), which could not be detected by the sodar. 相似文献
2.
Atmospheric profiling with the UAS SUMO: a new perspective for the evaluation of fine-scale atmospheric models 总被引：1，自引：0，他引：1
Stephanie Mayer Anne Sandvik Marius O. Jonassen Joachim Reuder 《Meteorology and Atmospheric Physics》2012,116(1-2):15-26
For the first time, unmanned aerial system measurements collected by the small unmanned meteorological observer (SUMO) are used to evaluate atmospheric boundary layer (ABL) parameterization schemes embedded in the Advanced Weather Research and Forecasting model (AR-WRF). Observation sites were located in the vicinity of the almost idealized shaped mountain Hofsj?kull, Central Iceland. SUMO profiles provided temperature, relative humidity and wind data to maximum heights of 3?km above ground. Two cases are investigated, one with calm wind conditions and development of a convective ABL and one with moderate winds and gravity waves over Hofsj?kull. For the high-resolution simulation with AR-WRF, three two-way nested domains are chosen with a grid size of 9, 3 and 1?km. During its first meteorological test, SUMO has proved its great value for the investigation of the diurnal evolution of the ABL and the identification of mesoscale features residing above the ABL, such as subsidence. 相似文献
3.
Ekaterina Batchvarova Xiaoming Cai Sven-Erik Gryning Douw Steyn 《Boundary-Layer Meteorology》1999,90(1):1-20
The purpose of this paper is to test the ability of two quite different models to simulate the combined spatial and temporal variability of the internal boundary layer in an area of complex terrain and coastline during one day. The simple applied slab model of Gryning and Batchvarova, and the Colorado State University Regional Atmospheric Modelling System (CSU-RAMS) are tested by comparison with data gathered during a field study (called Pacific '93) of photochemical pollution in the Lower Fraser Valley of British Columbia, Canada. The data utilised here are drawn from tethered balloon flights, free flying balloon ascents, and downlooking lidar operated from an aircraft flown at roughly 3500 m above sea level. Both models are found to represent the temporal and spatial development of the internal boundary-layer depth over the Lower Fraser Valley very well, and reproduce many of the finer details revealed by the measurements. 相似文献
4.
5.
A. J. Lapworth 《Boundary-Layer Meteorology》1987,39(4):333-378
Wind profiles have been measured through daytime boundary-layer capping inversions at a site surrounded by fairly flat terrain. The measurements were made by an instrument package mounted on a tethered balloon cable. Analysis of the results has shown that in the region of the inversion, the wind profiles generally show strong shears and also relatively narrow jet or minima features that vary with time. The profiles have been compared with the results of simple one-dimensional models which reproduce several of the observed features. The comparison has shown that some of these features are a result of inertial oscillations taking place in the stable layer immediately above the inversion, and suggests that the oscillations are coherent over a distance of hundreds of kilometres. Although their origin is related to that of the noctural jet, the daytime jets observed have a different structure due to the elevation of the stable layer. In particular, a narrow jet is formed when the inertial oscillation is at its minimum. This has no counterpart in the nocturnal case. 相似文献
6.
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
7.
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
8.
S. Khodayar N. Kalthoff M. Fiebig-Wittmaack M. Kohler 《Meteorology and Atmospheric Physics》2008,99(3-4):181-198
Summary The boundary-layer structure of the Elqui Valley is investigated, which is situated in the arid north of Chile and extends
from the Pacific Ocean in the west to the Andes in the east. The climate is dominated by the south-eastern Pacific subtropical
anticyclone and the cold Humboldt Current. This combination leads to considerable temperature and moisture gradients between
the coast and the valley and results in the evolution of sea and valley wind systems. The contribution of these mesoscale
wind systems to the heat and moisture budget of the valley atmosphere is estimated, based on radiosoundings performed near
the coast and in the valley.
Near the coast, a well-mixed cloud-topped boundary layer exists. Both, the temperature and the specific humidity do not change
considerably during the day. In the stratus layer the potential temperature increases, while the specific humidity decreases
slightly with height. The top of the thin stratus layer, about 300 m in depth, is marked by an inversion. Moderate sea breeze
winds of 3–4 m s−1 prevail in the sub-cloud and cloud layer during daytime, but no land breeze develops during the night.
The nocturnal valley atmosphere is characterized by a strong and 900 m deep stably stratified boundary layer. During the day,
no pronounced well-mixed layer with a capping inversion develops in the valley. Above a super-adiabatic surface layer of about
150 m depth, a stably stratified layer prevails throughout the day. However, heating can be observed within a layer above
the surface 800 m deep. Heat and moisture budget estimations show that sensible heat flux convergence exceeds cold air advection
in the morning, while both processes compensate each other around noon, such that the temperature evolution stagnates. In
the afternoon, cold air advection predominates and leads to net cooling of the boundary layer. Furthermore, the advection
of moist air results in the accumulation of moisture during the noon and afternoon period, while latent heat flux convergence
is of minor relevance to the moisture budget of the boundary layer.
Correspondence: Norbert Kalthoff, Institut für Meteorologie und Klimaforschung, Universit?t Karlsruhe/Forschungszentrum Karlsruhe,
Postfach 3640, 76021 Karlsruhe, Germany 相似文献
9.
兰州市冬季大气边界层结构特征的观测和数值模拟研究 总被引：7，自引：1，他引：7
本文利用甘肃省政府和中国科学院的科技合作项目"兰州市大气污染及对策研究"所获得的系留气球探空资料,并且结合数值模拟方法,对兰州市冬季大气边界层温度场特征进行了对比分析,结果表明:在没有特殊天气过程的典型冬季代表性时段,山谷城市兰州逆温边界层结构无论白天或夜间都存在,而且经常出现多层逆温和白天的脱地逆温情况,只有当冷空气过境时,逆温现象才减弱或消失;与观测结果相比较可以看出,数值模拟结果基本上反应了温度场的主要特征。 相似文献
10.
The high-power Defford radar has been upgraded to provide Doppler information regarding the motion of echoes from weak refractive index inhomogeneities within the optically clear atmosphere. A case study is presented in which data from the radar are used to derive the detailed velocity structure in and above the planetary boundary layer. These data are analysed to show how convective circulations in the boundary layer can perturb the height of a shallow inversion overlying it, thereby producing local enhancements of wind shear and a decrease in dynamic stability within the inversion. The measurements were obtained as part of a Boundary-Layer Project in which simultaneous measurements were made using fast-response instruments suspended from a tethered balloon within the region scanned by the radar. The balloon-borne probes showed that the most intense turbulence and fluctuations of temperature and refractivity were encountered when radar-detected hummocks in the height of the inversion were advected through the probes. The fine-scale turbulence measurements within the perturbed inversion are consistent with the existence of Kelvin-Helmholtz billows. 相似文献
11.
Results from radiosoundings, performed both over land and over sea, show that the ascent rate of a radiosounding balloon, the vertical velocity of the balloon, can be used to determine the height of the boundary layer. In many cases the balloon has a higher ascent rate in the boundary layer and a lower, less variable, ascent rate above. The decrease in ascending velocity appears as a jump at the top of the boundary layer. Two examples of potential temperature profiles for unstable stratification and one profile for stable conditions are shown with the corresponding ascent rates. A comparison between the boundary-layer height determined from potential temperature profiles and from ascent rates is presented for a larger dataset. The different ascent rates of the balloon in the boundary layer and above can be explained by a decrease in drag on the balloon in combination with a lowering of the critical Reynolds number in the boundary layer caused by turbulence. Hence, by simply logging the time from release of a radiosonde, it is possible to obtain additional information that can be used to estimate the height of both the unstable and stable boundary layers. 相似文献
12.
Detailed measurements of profiles of mean and turbulent variablesthrough the nocturnal stable boundary layer over a valley arepresented. Two nights of data are analysed in detail, one with only aweakly stable boundary layer and one with a strongly stable boundarylayer. The weakly stratified night shows high levels of turbulence inwhich the flow remains attached to the valley and the boundary layeracts as a single coherent layer. On the strongly stratified night, twoflow regimes are identified: attached flow, as on the weaklystratified night, and decoupled flow in which the air in the valleybecomes so dynamically stable that there is no turbulent interactionwith the mean flow aloft. Because the valley is sloping, the decoupledlower stagnant air then forms a drainage current. We find that theFroude number evaluated at the hill height, FH = U(H)/N(H) H,diagnoses the flow regime: when FH = 2, the flow remainsattached and when FH 2 the flow in the valley becomesdecoupled from the flow aloft. The dynamics of the flow regimes areshown to be understandable in terms of the gradient Richardson number,which indicates the turbulent mixing. We show that the gradientRichardson number is a key parameter in diagnosing each flow regime. 相似文献
13.
A. Lapworth 《Boundary-Layer Meteorology》2006,119(3):501-526
Six years of observations from a surface instrument site have been analysed to determine timings and factors influencing developmental changes in the near-surface wind and turbulent heat fluxes during the morning heating of the atmospheric boundary layer. A simple relationship has been found between near-surface wind speed and screen temperature, together with a predictive equation for the morning transition air temperature. Profile measurements from a probe mounted on a tethered balloon have beenused to supplement the surface data and study the processes underlying these surface relationships. The results have confirmed earlier work and have shown that both before and immediately after morning transition, almost all heating in the surface layer is due to turbulent diffusion from above. In order to explain the mechanisms involved in the relationships, a simple finite difference model has been run and validated against the profile data. The model predictions are compared with observations during both the morning and evening and the differences related to the different temperature profiles. Numerical forecasting rules for the surface wind speed and transition temperature are derived from the results. 相似文献
14.
Zhou Mingyu Chen Jingnan Li Shiming Zheng Yueming Su Lirong L&#;Naiping 《Acta Meteorologica Sinica》1991,5(3):331-341
A Doppler sodar system controlled by microcomputer is described in this paper. The sodar was usedto detect the vertical distribution of wind and temperature stratification in the atmospheric boundary layer.The detecting results show that at night the vertical distribution of wind is very complicated, which can appearas a structure of two or three layers. In nocturnal atmospheric boundary layer sometimes there exists verythin layer in multi-layer inversion and it can be retained for a long time. 相似文献
15.
系留气艇探测风速的误差订正及其应用评估 总被引：1，自引：1，他引：0
使用系留气艇探空系统在常州、苏州、南京市区对边界层风速、温度、湿度廓线进行了观测,原始数据表明探测结果存在明显的系统误差。本文主要讨论风速订正问题,分析发现风速误差与高度和风速有关,据此提出了依据高度和依据风速的两种订正方案。对比结果表明:两种方案都能有效修正系留气艇测量风速的系统误差,高度订正方案表现更好。本文还用订正后的系留气艇探测结果与苏州市气象局的风廓线雷达资料进行对比,结果显示风廓线雷达探测结果在500 m以下系统偏小。 相似文献
16.
V. A. Drake 《Boundary-Layer Meteorology》1984,28(3-4):353-374
A special-purpose radar has been used to observe the vertical distribution of large, strong-flying insects migrating in the nocturnal boundary layer over the central-western plains region of New South Wales. During the period of take-off flight at dusk, the density of insects decreased monotonically with height, and a distribution of this type persisted for much of the night in the zone of steady temperature lapse extending from the top of the inversion layer to the flight ceiling at about 1 km. Later in the night, the insects often became concentrated in the warm air at the top of the inversion layer. The lower boundary of this concentration sometimes became sharply defined, but above the zone of maximum insect density there was usually a smooth decrease of insect numbers with altitude. When the boundary layer was disturbed by an atmospheric density current, the direction and vertical distribution of the migration was permanently changed; solitary wave disturbances, however, had only a transient effect. 相似文献
17.
苏州东山冬季大气边界层结构特征及其对污染物浓度的影响 总被引：5，自引：1，他引：5
利用2015年1月15—27日在苏州东山气象观测站系留气艇观测数据以及细颗粒物浓度观测资料,对东山大气边界层结构特征及其对污染物垂直结构分布的影响进行分析研究。结果表明:苏州东山地区冬季空气污染过程的边界层结构演变比较典型,夜间稳定边界层高度约为200 m,白天最大边界层高度可达1 000 m。边界层内污染物垂直结构分布易受边界层高度的影响,较低的大气边界层高度可使细颗粒物在近地层持续累积;反之,边界层高度较高,湍流发展旺盛,颗粒物垂直分布均匀。夜间大气边界层稳定,逆温结构多发,导致近地面出现细颗粒物堆积。风的垂直结构对细颗粒物空间分布也存在显著影响,在风速较小的低空层细颗粒分布较多,而风速较大的中高层的分布较少。 相似文献
18.
The results of an observational and modeling study of the nocturnal slope winds in a simple valley are presented. The valley was approximately 225 m deep in the region of the measurements, and featured a uniform slope angle of approximately 23 ° on one of its sidewalls. The wind and temperature structure of the katabatic flows on the valley sidewalls were measured with tower-mounted instruments, and a Doppler sodar and instruments on a tethered balloon and a 61-m tower were used to determine the atmospheric conditions near the center of the valley. The temperature structure of the slope flows was summarized by characteristic scale parameters h and T for the inversion depth and strength, respectively. On the sidewalls 50 m above the valley floor, the inversion depths were generally smaller and the inversion strengths were weaker than they were on the sidewalls 100 m higher. These results differ significantly from those obtained over a simple slope of an isolated mountain or ridge. The down-valley winds are shown to be important in limiting the strength of the sidewall inversions. The formation of an inversion in the valley also has a pronounced effect on the structure of the slope flows. Numerical simulations suggest that the presence of adiabatic layers in the valley atmosphere is associated with decreases in the slope-flow inversion depth with increasing downslope distance. The simulations also indicate that the length scales that characterize the momentum and inversion depths behave similarly in flows down simple slopes but not in flows down the sidewalls of a valley.Work supported by the U.S. Army Research Office under Contract DA-AG29-K-0231 and the U.S. Department of Energy under Contract DE-AC06-76RLO 1830. 相似文献
19.
Features associated with the upper limit of convection, observed by turbulence probes supported by a tethered kite balloon and by high-power Doppler radar, are described. The observations illustrate the interaction of thermal plumes with the capping inversion (and stable air aloft) and confirm the existence of non-turbulent, intermittently turbulent and fully turbulent layers. Evidence is presented for entrainment processes occurring on scales ranging from a few metres to several hundred metres. Individual distortions of the inversion interface, tracked by the radar, have a lifetime of about 5 minutes. Other, larger scale (i.e., > 1 km) perturbations of the top of the boundary layer were observed over longer periods, and are thought to be due to topographical effects. 相似文献
20.
BOUNDARY LAYER GROWTH AND LAPSE RATE CHANGES DETERMINED BY LIDAR AND SURFACE HEAT FLUX IN SOFIA* 
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下载免费PDF全文 In this study the results from a boundary layer experiment,conducted in autumn 1991 over a flat,build-up urban area in Southeast Sofia,together with some models for mixed layer growth rates are used to investigate the layered structure of the vertical atmospheric stability distribution in the Sofia Valley.Lidar measurements of aerosol layer heights and morning boundary layer development are combined with surface eddy correlation measurements of kinematic heat and moisture fluxes,profiles of temperature and humidity,wind speed and wind direction.A diagnostic method is presented for determining vertical lapse rates using surface meteorological measurements and lidar returns observed during the transition from nighttime stable stratification to daytime convective boundary layer after the sunrise. 相似文献