共查询到10条相似文献,搜索用时 93 毫秒
1.
Renzo Richiardone Elena Giampiccolo Silvia Ferrarese Massimiliano Manfrin 《Boundary-Layer Meteorology》2008,128(2):277-302
We describe the coordinate transformations that can be used to convert the velocity components measured by a set of sonic
anemometers with time-dependent tilt fluctuations into a single, time-independent coordinate system. By applying the planar
fit method (PFM) to each anemometer dataset, it is possible, for planar flows, to locate the flow plane at each measurement
point and compare its orientation with the topography. Installation on a ship is also considered. An application of this method
to intercomparison data has led to the detection of an instrument error due to a misalignment between the assembly of the
sonic transducers and the anemometer pedestal. If this error occurs, pedestal levelling does not guarantee that measurements
are unbiased. A correction method is proposed and the results of two experiments are shown. Flow planarity at different levels
and flow distortion caused by the mast are highlighted. The influence of the error on the evaluation of the Reynolds stresses
using PFM or the double rotation method and the triple rotation method is discussed and the tilt corrected stresses calculated
using the three methods compared. 相似文献
2.
Hyun-Mi Oh Kyung-Ja Ha Ki-Young Heo Kyung-Eak Kim Sang-Jong Park Jae-Seol Shim Larry Mahrt 《Asia-Pacific Journal of Atmospheric Sciences》2010,46(4):513-523
This study presents an evaluation of the atmospheric factors influencing the post-processing for fast-response data of horizontal momentum, vertical wind component, temperature, and water vapor to measure turbulent fluxes. They are observed at the Ieodo ocean research station over the Yellow Sea during the period of October 2004 to February 2008. The post process methods employed here are composed of quality control and tilt correction for turbulent flux measurement. The present result of quality control on the fast-response data shows that total removal ratio of the data generally depends on the factors such as a wind speed, relative humidity, significant wave height, visibility, and stability parameter (z/L). Especially, the removal ratio of water vapor data is significantly increased on light wind and strong stability conditions. The results show that the total removal ratio of water vapor data increases when wind speed is less than 3 m s?1 and wave height is less than 1 m. The total removal ratio of water vapor data also increases with the value of the stability parameter. Three different algorithms of tilt correction methods (double rotation, triple rotation, and planar fit) are applied to correct the tilt of the sonic anemometer used in the observation. Friction velocities in near neutral state are greater than friction velocity in other states. Drag coefficients are categorized in terms of stabilities and seasons. 相似文献
3.
A perturbation theory approach of non-linear mechanics is applied to the solution of a non-linear rotation anemometer dynamic equation in a gusty wind. The first two terms of the perturbation series give a simplified equation for the wind-speed overestimation by a rotation anemometer (u-error) in terms of a wind velocity spectrum (or a correlation function). The equation agrees satisfactorily with all the known analytical or numerical solutions of rotation anemometer equations. It agrees, in particular, with recent theoretical estimations of the u-error magnitude by Kondo et al. (1971) and Hyson (1972), but disagrees significantly with the experimental findings of Izumi and Barad (1970) and Högström (1974). The same approach is also used for the estimation of the influence of the vertical wind fluctuations on the rotation anemometer readings (w-error). It is shown that w-error is usually of the same sign as u-error and that the sum of these both types of errors may be in some cases of the same order as an experimental wind-speed overestimation observed by Izumi and Barad and by Högström. However, it seems probable that some additional types of errors contribute also to the real overspeeding of rotation anemometers in a gusty wind. 相似文献
4.
LIU Li WANG Tijian SUN Zhenhai WANG Qingeng ZHUANG Bingliang HAN Yong LI Shu 《大气科学进展》2012,29(6):1264-1278
Turbulence characteristics of an atmospheric surface layer over a coastal mountain area were investigated under different coordinate frames.Performances of three methods of coordinate rotation:double rotation(DR),triple rotation(TR),and classic planar-fit rotation(PF) were examined in terms of correction of eddy covariance flux.Using the commonly used DR and TR methods,unreasonable rotation angles are encountered at low wind speeds and cause significant run-to-run errors of some turbulence characteristics.The PF method rotates the coordinate system to an ensemble-averaged plane,and shows large tilt error due to an inaccurate fit plane over variable terrain slopes.In this paper,we propose another coordinate rotation scheme.The observational data were separated into two groups according to wind direction.The PF method was adapted to find an ensemble-averaged streamline plane for each group of hourly runs with wind speed exceeding 1.0 m s 1.Then,the coordinate systems were rotated to their respective bestfit planes for all available hourly observations.We call this the PF10 method.The implications of tilt corrections for the turbulence characteristics are discussed with a focus on integral turbulence characteristics,the spectra of wind-velocity components,and sensible heat and momentum fluxes under various atmospheric stabilities.Our results show that the adapted application of PF provides greatly improved estimates of integral turbulence characteristics in complex terrain and maintains data quality.The comparisons of the sensible heat fluxes for four coordinate rotation methods to fluxes before correction indicate that the PF10 scheme is the best to preserve consistency between fluxes. 相似文献
5.
A wind velocity measuring system based on the Gill propeller anemometer is described. A method of calculating the vertical component, which allows for the non-cosine response and avoids the region of stall and nonlinear operation, is presented. A summary of the possible errors in Reynolds stress and drag coefficient estimates is given. A method of establishing the distance constant using field observations is presented. Finally, some preliminary results and some intercomparisons with otheranemometers are described briefly. 相似文献
6.
A wind velocity measuring system based on the Gill propeller anemometer is described. A method of calculating the vertical component, which allows for the non-cosine response and avoids the region of stall and nonlinear operation, is presented. A summary of the possible errors in Reynolds stress and drag coefficient estimates is given. A method of establishing the distance constant using field observations is presented. Finally, some preliminary results and some intercomparisons with other anemometers are described briefly.Now at the Institute of Ocean Sciences, Patricia Bay, B.C., Canada. 相似文献
7.
8.
J. Wieringa 《Boundary-Layer Meteorology》1972,2(4):406-426
For 390 ten-minute samples of turbulent flux, made with a trivane above a lake, the vertical alignment is determined within 0.1 ° through azimuth-dependent averaging. One degree of instrumental misalignment is found to produce an average tilt error of 9 ± 4% for momentum flux, and 4 ± 2% for heat flux. The tilt error in the vertical momentum flux depends mainly ons
u/u*, and cannot be much diminished with impunity by high-pass pre-filtering of the turbulence signals. The effects of rain on trivane measurements of vertical velocity are shown to be negligible at high wind speeds, and adaptable to correction in any case.The normalized vertical velocity variance,s
w/u*, appears to be proportional to the square root ofz/L for unstable stratification. For a wind speed range of 2 to 15 m s–1, the eddy correlation stresses measured at 4- and 8-m heights can be reasonably well estimated by using a constant drag coefficientC
d=1.3 X 10-3, while cup anemometer profile measurements give an overestimate of eddy stress at high wind speeds. A good stress estimate is also obtained from the elevation variance; it is suggested that trivane measurement of this variance might be made from a mobile platform, e.g., a moderately stabilized spar buoy. 相似文献
9.
Remarks on the Definition and Estimation of Friction Velocity 总被引:3,自引:1,他引:2
Rudolf O. Weber 《Boundary-Layer Meteorology》1999,93(2):197-209
One of the mainscaling parameters in similarity theory of the atmospheric boundary layer is friction velocity. Unfortunately, several definitions of friction velocity exist in the literature. Some authors use the component of the horizontal Reynolds stress vector in the direction of the mean wind vector to define friction velocity. Others define the friction velocity by means of the absolute value of the horizontal Reynolds stress vector. The two definitions coincide only if the direction of the mean wind vector is parallel to the horizontal Reynolds stress vector. In general, the second definition gives larger values for the friction velocity. Over complex terrain the situation is further complicated by the fact that the terrain following flow is not necessarily horizontal. Thus, several authors have proposed to use terrain following coordinate systems for the definition of friction velocity. By means of a large dataset of fast-response wind measurements with an ultrasonic anemometer the friction velocities resulting from the different definitions are compared. Furthermore, it is shown that friction velocity can be well estimated from horizontal wind speed, and even better from simple horizontal or vertical turbulence parameters. 相似文献
10.
Errors in turbulence measurements with a sonic anemometer 总被引:1,自引:0,他引:1
Errors in surface-layer wind data obtained by sonic anemometers are estimated as a function of relative wind direction using a comparison between two identical anemometers. The maximum errors in mean windspeed and the standard deviations of the horizontal wind components are found to be between 10 and 20%. Agreement between the size of the measured errors and those calculated from wind-tunnel data is fair.In addition, vertical velocity data are analysed to show the presence of flow distortion induced by the asymmetry in the sonic anemometer probe and the mounting of the probe on the top of a mast. 相似文献