共查询到20条相似文献,搜索用时 31 毫秒
1.
Christoph Münkel Noora Eresmaa Janne Räsänen Ari Karppinen 《Boundary-Layer Meteorology》2007,124(1):117-128
The Vaisala ceilometers CT25K and CL31 are eye-safe single lens lidar systems reporting attenuated backscatter profiles; they
often operate 24 h a day in fully automated, hands-off operation mode. These profiles can be used for more than just cloud-base
height determination. In dry weather situations, there is a fairly good correlation between the ceilometer near-range backscatter
and in situ PM10 concentration readings. The comparison of mixing height values based on soundings and on ceilometer backscattering
profiles indicates that ceilometers are suitable instruments for determining the convective mixing height. Its enhanced optics
and electronics enables the CL31 ceilometer to detect fine boundary-layer structures whose counterparts are seen in temperature
profiles. 相似文献
2.
Evaluation of Mixing-Height Retrievals from Automatic Profiling Lidars and Ceilometers in View of Future Integrated Networks in Europe 总被引:2,自引:0,他引:2
M. Haeffelin F. Angelini Y. Morille G. Martucci S. Frey G. P. Gobbi S. Lolli C. D. O’Dowd L. Sauvage I. Xueref-Rémy B. Wastine D. G. Feist 《Boundary-Layer Meteorology》2012,143(1):49-75
The determination of the depth of daytime and nighttime mixing layers must be known very accurately to relate boundary-layer concentrations of gases or particles to upstream fluxes. The mixing-height is parametrized in numerical weather prediction models, so improving the determination of the mixing height will improve the quality of the estimated gas and particle budgets. Datasets of mixing-height diurnal cycles with high temporal and spatial resolutions are sought by various end users. Lidars and ceilometers provide vertical profiles of backscatter from aerosol particles. As aerosols are predominantly concentrated in the mixing layer, lidar backscatter profiles can be used to trace the depth of the mixing layer. Large numbers of automatic profiling lidars and ceilometers are deployed by meteorological services and other agencies in several European countries providing systems to monitor the mixing height on temporal and spatial scales of unprecedented density. We investigate limitations and capabilities of existing mixing height retrieval algorithms by applying five different retrieval techniques to three different lidars and ceilometers deployed during two 1-month campaigns. We studied three important steps in the mixing height retrieval process, namely the lidar/ceilometer pre-processing to reach sufficient signal-to-noise ratio, gradient detection techniques to find the significant aerosol gradients, and finally quality control and layer attribution to identify the actual mixing height from multiple possible layer detections. We found that layer attribution is by far the most uncertain step. We tested different gradient detection techniques, and found no evidence that the first derivative, wavelet transform, and two-dimensional derivative techniques have different skills to detect one or multiple significant aerosol gradients from lidar and ceilometer attenuated backscatter. However, our study shows that, when mixing height retrievals from a ultraviolet lidar and a near-infrared ceilometer agreed, they were 25?C40% more likely to agree with an independent radiosonde mixing height retrieval than when each lidar or ceilometer was used alone. Furthermore, we point to directions that may assist the layer attribution step, for instance using commonly available surface measurements of radiation and temperature to derive surface sensible heat fluxes as a proxy for the intensity of convective mixing. It is a worthwhile effort to pursue such studies so that within a few years automatic profiling lidar and ceilometer networks can be utilized efficiently to monitor mixing heights at the European scale. 相似文献
3.
Comparing mixing-length models of the diabatic wind profile over homogeneous terrain 总被引:1,自引:0,他引:1
Alfredo Peña Sven-Erik Gryning Charlotte Bay Hasager 《Theoretical and Applied Climatology》2010,100(3-4):325-335
Models of the diabatic wind profile over homogeneous terrain for the entire atmospheric boundary layer are developed using mixing-length theory and are compared to wind speed observations up to 300 m at the National Test Station for Wind Turbines at Høvsøre, Denmark. The measurements are performed within a wide range of atmospheric stability conditions, which allows a comparison of the models with the average wind profile computed in seven stability classes, showing a better agreement than compared to the traditional surface-layer wind profile. The wind profile is measured by combining cup anemometer and lidar observations, showing good agreement at the overlapping heights. The height of the boundary layer, a parameter required for the wind profile models, is estimated under neutral and stable conditions using surface-layer turbulence measurements, and under unstable conditions based on the aerosol backscatter profile from ceilometer observations. 相似文献
4.
A radio acoustic sounding system (RASS), operating at an acoustic frequency ƒ 360 Hz, proved to be capable of measuring the vertical temperature profile in the planetary boundary layer (PBL) with an accuracy and vertical resolution comparable to those of traditional apparatus (radiothermosondes borne by tethered or disposable balloons, thermosondes borne by aircraft and so on, yet combined with the advantages typical of remote sensing techniques.Since summer 1983 the system has been running in a completely automatic way by means of a microprocessor and can provide the average thermal profile at preset time intervals (typically 0.5 h). (Previously, the acoustic sounding frequency affording the fundamental condition of Bragg resonance between acoustic and radio wavelengths had to be identified by an operator).The maximum range of measurement has been 1000 m in 50% of cases. Temperature measurements are reliable from an altitude of a few tens of meters.Results for different thermodynamic stability conditions, together with good performances achieved in adverse atmospheric conditions such as strong wind, snow, rain, etc., are presented here.Such results indicate the usefulness of the automatic RASS as a tool for meteorological purposes and for the application of air pollution control strategies.Maximum sounding range attained for different areas of the acoustic antenna is also analysed in order to evaluate the performance of an automatic mobile RASS. 相似文献
5.
John R. Taylor Nathan J. Segal Michael R. Bradshaw David J. Low 《Meteorology and Atmospheric Physics》2013,119(3-4):197-206
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. 相似文献
6.
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 相似文献
7.
D. Engelbart H. Steinhagen U. Görsdorf J. Neisser H. J. Kirtzel G. Peters 《Meteorology and Atmospheric Physics》1999,71(1-2):61-68
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 相似文献
8.
Aggeliki Dandou Maria Tombrou Klaus Schäfer Stefan Emeis Anna P. Protonotariou Elissavet Bossioli Nikolaos Soulakellis Peter Suppan 《Boundary-Layer Meteorology》2009,131(3):425-440
An attempt is made to correlate the mixing heights, derived from ceilometer and Sodar measurements, to those simulated by
different atmospheric boundary-layer parameterization schemes. The comparison is performed at two sites (one suburban and
one rural) close to Munich, Germany for two spring and two winter days. It is found that, under convective conditions, the
mixing height determined, by both Sodar and ceilometer, corresponds to the middle or the top of the entrainment zone, respectively,
as calculated from the eddy-viscosity profiles. Under stable conditions, the measured mixing height is related to the height
where eddy viscosities attain their minimum values (Sodar) or to the height of residual mechanical turbulence (ceilometer).
During a foehn case with weak turbulence, the measured mixing height from both Sodar and ceilometer is better inferred by
considering the eddy-viscosity profiles during daytime and the height of the low-level jet during nighttime. 相似文献
9.
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 相似文献
10.
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 相似文献
11.
Measurements and Parametrizations of the Atmospheric Boundary-Layer Height at Dome C,Antarctica 总被引:2,自引:2,他引:0
Ilaria Pietroni Stefania Argentini Igor Petenko Roberto Sozzi 《Boundary-Layer Meteorology》2012,143(1):189-206
An experimental campaign, Study of the Atmospheric Boundary Layer Environmental at Dome C, was held during 2005 at the French-Italian
station of Concordia at Dome C. Ground-based remote sensors, as well as in situ instrumentation, were used during the experimental
campaign. The measurements allowed the direct estimation of the polar atmospheric boundary-layer height and the test of several
parametrizations for the unstable and stable boundary layers. During the months of January and February, weak convection was
observed while, during the polar night, a long-lived stable boundary layer occurred continuously. Under unstable stratification
the mixing-layer height was determined using the sodar backscattered echoes and potential temperature profiles. The two estimations
are highly correlated, with the mixing height ranging between 30 and 350 m. A simple prognostic one-dimensional model was
used to estimate the convective mixing-layer height, with the correlation coefficient between observations and model results
being 0.66. The boundary-layer height under stable conditions was estimated from radiosounding profiles as the height where
the critical Richardson number is reached; values between 10 and 150 m were found. A visual inspection of potential temperature
profiles was also used as further confirmation of the experimental height; the results of the two methods are in good agreement.
Six parametrizations from the literature for the stable boundary-layer height were tested. Only the parametrization that considers
the long-lived stable boundary layer and takes into account the interaction of the stable layer with the free atmosphere is
in agreement with the observations. 相似文献
12.
乔晓燕 《沙漠与绿洲气象(新疆气象)》2020,14(3):137-143
利用2016年10月~2017年2月激光云高仪资料,分析了霾、雾、轻霾、轻雾、晴空等天气后向散射强度廓线特征,通过统计各高度层后向散射强度、后向散射强度垂直梯度的概率分布,分析了多种天气的气溶胶光学特性。结果表明:雾天气后向散射强度较霾天气大,雾厚度一般不超过300m。霾天气后向散射强度随着高度的增加减小缓慢,霾的厚度大于500m。与雾和轻雾相比,霾和轻霾天气垂直梯度绝对值取小值的概率较大。雾和轻雾天气400m高度以上垂直梯度绝对值较小,400m高度以下数值较大。由于霾区内粒子分布较均匀,雾区粒子分布起伏明显,雾区内后向散射强度忽大忽小,所以雾天气垂直梯度绝对值出现大值的概率较霾天气高。 相似文献
13.
Hironori Iwai Yasuhiro Murayama Shoken Ishii Kohei Mizutani Yuichi Ohno Taichiro Hashiguchi 《Boundary-Layer Meteorology》2011,141(1):117-142
To study the wind field within the atmospheric boundary layer over the Tokyo metropolitan area, Doppler lidar observations
were made 45 km north of Sagami Bay and 30 km west of Tokyo Bay, from 14 May to 15 June 2008. Doppler lidar on 27 May 2008
observed the vertical and horizontal wind structure of a well-developed sea-breeze front (SBF) penetrating from Sagami Bay.
At the SBF, a strong updraft (maximum w approximately equal to 5 m s−1) was formed with a horizontal scale of about 500 m and vertical scale of 2 km. The spatial relationship between the strong
updraft over the nose of the SBF and prefrontal thermal suggests that the strong updraft was triggered by interaction between
the SBF and the thermal. After the updraft commenced, a collocated ceilometer observed an intense aerosol backscatter up to
2 km above ground level. The observational results suggest that the near-surface denser aerosols trapped in the head region
of the SBF escaped from the nose of the SBF and were then vertically transported up to the mixing height by the strong updraft
at the SBF. This implies that these phenomena occurred not continuously but intermittently. The interaction situations between
the SBF and prefrontal thermal can affect the wind structure at the SBF and the regional air quality. 相似文献
14.
Twenty-six months of continuous ceilometer data are used to estimate the convective mixed-layer height for 710 days by identifying
backscatter gradients associated with the entrainment zone. To accomplish this, a semi-automatic procedure is developed that
removes all non-applicable data before applying a mixed-layer height algorithm to the backscatter profiles. Two different
algorithms for estimating the mixed-layer height are assessed: the minimum-gradient method and the ideal-profile method. The
latter of these two algorithms is found to be more robust. Comparisons of mixed-layer height values estimated from the ceilometer
agree with previous observations with slightly higher estimates in the mornings and evenings. For clear days with no cumulus
cloud formation, the seasonal cycle in mixed-layer heights peaks in late June to early July. Daily maximum values are suppressed
by the site’s coastal location, remaining below 800 m for all but a few days. The mean daily maximum mixed-layer height increases
by 384 m for days with boundary-layer clouds. The mean summer diurnal trend is found not to differ greatly from that in spring
on clear days, while days with boundary-layer clouds have higher spring values than in summer. Net surface heat flux and synoptic
stability likely have the largest influence on the mixed-layer heights. Additionally, large intra-monthly variability suggests
a strong influence from regional dynamics. 相似文献
15.
16.
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 相似文献
17.
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
18.
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%. 相似文献
19.
Measurements and Modelling of the Wind Speed Profile in the Marine Atmospheric Boundary Layer 总被引:1,自引:1,他引:0
We present measurements from 2006 of the marine wind speed profile at a site located 18 km from the west coast of Denmark
in the North Sea. Measurements from mast-mounted cup anemometers up to a height of 45 m are extended to 161 m using LiDAR
observations. Atmospheric turbulent flux measurements performed in 2004 with a sonic anemometer are compared to a bulk Richardson
number formulation of the atmospheric stability. This is used to classify the LiDAR/cup wind speed profiles into atmospheric
stability classes. The observations are compared to a simplified model for the wind speed profile that accounts for the effect
of the boundary-layer height. For unstable and neutral atmospheric conditions the boundary-layer height could be neglected,
whereas for stable conditions it is comparable to the measuring heights and therefore essential to include. It is interesting
to note that, although it is derived from a different physical approach, the simplified wind speed profile conforms to the
traditional expressions of the surface layer when the effect of the boundary-layer height is neglected. 相似文献
20.
In this paper, measurements of the first 150 m of the atmospheric boundary layer obtained by a high-frequency acoustic mini-sounder are compared with measurements obtained by a full complement of instruments including sonic anemometers mounted on the Boulder Atmospheric Observatory tower. The acoustic mini-sounder, starting as low as 6 m from the ground, measures in the monostatic mode the profiles of the vertical wind speed, w, and of the temperature structure parameter, C T 2 with enhanced height resolution of the order of 1 m and time resolution of the order of 30 s. The results of the comparison show that the high-frequency mini-sounder is an effective atmospheric boundary-layer profiler that is also portable and relatively inexpensive. Measurements of the spectrum of C T 2 are presented that provide information on the local isotropy of the temperature field. Statistics of the variability of C T 2 in both stable and unstable conditions are also given. The sounder's capabilities are further demonstrated by some detailed observations of the structure and time evolution of a thermal plume root at noon and of a nocturnal, stably stratified layer in which a dynamic instability develops. The plume starts at a height of less than 5 m, possesses substantial internal structure, and includes vertical velocities in excess of 2 m s-1. 相似文献