共查询到20条相似文献，搜索用时 15 毫秒
1.
Gerhard Kramm 《Boundary-Layer Meteorology》1989,48(3):315-327
The estimation of the surface-layer parameters u
* (friction velocity), * and q
* (temperature and humidity scales),
r
and q
r (temperature and humidity reference values), z
o (roughness length) and d (zero-displacement) from vertical profiles of wind velocity, temperature and humidity by least-squares methods is described. The estimation is based on the flux-gradient relationships and the constant flux assumption for the transfer of momentum, sensible heat and matter near the Earth's surface.Test calculations were carried out with the vertical profile data from the GREIV I 1974 experiment and the Great Plains Turbulence Project. 相似文献
2.
John L. Walmsley 《大气与海洋》2013,51(2):203-233
Abstract In October 1985, the Boundary‐Layer Research Division of the Atmospheric Environment Service conducted an experiment on Sable Island, Nova Scotia, where 10‐m wind measurements were made at a number of locations. Wind data were also collected at 4 levels on one of the 10‐m masts and at 6 levels on a 26‐m mast, both located on the South Beach. Other data used in the present study consisted of air temperature measured at 9 m and sea temperature measured at the beach. The theory for wind speed and temperature profiles over the sea is reviewed. A method of deriving over‐sea profile parameters (u*, θ*, Z0, L) from wind data at one level and the air‐sea temperature difference is described. The method is limited to applications either over homogeneous open ocean or, provided measurements are taken above the internal boundary layer generated by the change of roughness at the coastline, over a flat beach (without coastal orography). The heights at which the method is applied must be within the surface layer which must not have any discontinuities in wind speed or temperature in the vertical, such as are often associated with inversion layers. An application to data collected at beach sites in onshore flow during the October 1985 experiment is illustrated. Once the above parameters are obtained, theoretical wind profiles may be computed and compared with observed profiles. In order to make a proper comparison it is essential to account for internal boundary layers generated at the shoreline by the step‐change in surface roughness. Only the data measured above the internal boundary layer are representative of over‐sea conditions and may, therefore, be used for verifying the theoretical profiles. The agreement between calculated and measured data is generally very good. One complication, however, is a slight upstream‐blockage effect due to a 7‐m high dune located about 140 m downwind of the 26‐m mast. Estimates of the magnitude of this effect partially account for small discrepancies in the results at the 26‐ and 10‐m mast locations. An estimation of the most probable errors in the calculated parameters, based on assumed measurement errors, is included in the computer program. Results suggest that small measurement errors can explain the above discrepancies. 相似文献
3.
High frequency measurements of wind velocity and temperature were made during the Ocean Storms Project in November 1987. The dissipation method was applied to the resulting time series in order to determine friction velocities,u
*, and the characteristic temperature scale,t
*, at 1-min intervals. These values were then compared to the 1-min mean wind speed and air-sea temperature differences to determine relationships for the drag coefficient (C
d
) and Stanton number (C
h
). The drag coefficient was comparable to other values reported in the literature, although the variation with wind speed was greater than reported by other investigators. An examination of the residual time series indicated a systematic low frequency periodicity of about 2-hr duration which was attributed to a fluctuating wind interacting with the surface gravity wave field. The temperature fluctuations did not produce meaningful estimates ofC
h
for stable conditions. For unstable conditions, a value of 1.09±0.02×10–3 was found. 相似文献
4.
A quantative transposition model is introduced which determines hourly wind speeds in a representative tropical region (Central Sudan). The model consists of two parts. Firstly, a local boundary-layer model, based on the energy balance equation and the Businger-Dyer equations, is used to compute the average diurnal cycle of various characteristic boundary-layer parameters. Secondly, a horizontal transposition method is introduced to calculate wind speed behaviour at an arbitrary station from that at a reference station. This method is based on assumed spatial constancy of the turbulence parameter u
* in the period November–April in a region of about (700 × 800) km2 in Central Sudan. The constancy of u
* is concluded from the very stationary character of the climate. Model-computed hourly wind speeds are consistent with the potential wind speeds (at 10 m over open country) calculated from the measured data, and provide better local wind estimates than the conventional procedure which assumes constant regional hourly wind speeds. 相似文献
5.
This contribution investigates the nature of turbulent kinetic energy (TKE) in a steep and narrow Alpine valley under fair-weather
summertime conditions. The Riviera Valley in southern Switzerland was chosen for a detailed case study, in which the evaluation
of aircraft data (obtained from the MAP-Riviera field campaign) is combined with the application of high-resolution (350-m
horizontal grid spacing) large-eddy simulations using the numerical model ARPS. The simulations verify what has already been
observed on the basis of measurements: TKE profiles scale surprisingly well if the convective velocity scale w
* is obtained from the sun-exposed eastern slope rather than from the surface directly beneath the profiles considered. ARPS
is then used to evaluate the TKE-budget equation, showing that, despite sunny conditions, wind shear is the dominant production
mechanism. Therefore, the surface heat flux (and thus w
*) on the eastern slope does not determine the TKE evolution directly but rather, as we believe, indirectly via the interaction
of thermally-driven cross-valley and along-valley flows. Excellent correlation between w
* and the up-valley wind speed solidifies this hypothesis. 相似文献
6.
Isidro A. Pérez M. Luisa Sánchez M. ángeles García 《Theoretical and Applied Climatology》2012,107(1-2):247-253
Temperature and wind speed profiles obtained from 3?years of radio acoustic sounding system sodar measurements at a rural site in the northern Spanish plateau were fitted to polynomial functions. Depending on the extrema of these fits, several groups of profiles were considered. Daily evolution of temperature profiles corresponded to the lower boundary layer evolution. However, wind speed profiles revealed a frequent low-level jet during the whole day. CO2 surface concentrations were analysed, and surface CO2 dilution was also considered by selection of thin canopies with variable depth, resulting in dilution rates of 7 and 18?ppm when the layer increased 100?m for the 95th percentile and temperature and wind speed profiles, respectively. 相似文献
7.
Profiles of wind velocity and temperature in the outer region of the atmospheric boundary layer (ABL) were used together with surface temperature measurements, to determine regional shear stress and sensible heat flux by means of transfer parameterizations on the basis of bulk similarity. The profiles were measured by means of radiosondes and the surface temperatures by infrared radiation thermometry over hilly prairie terrain in northeastern Kansas during the First ISLSCP Field Experiment (FIFE). In the analysis, the needed similarity functions were determined and tested; the main scaling variables used for the ABL were h
i
, the height of the convectively mixed layer, and V
a
and a, the wind speed and potential temperature averaged over the mixed layer. Good agreement (r = 0.80) was obtained between values of friction velocity u
*
determined by this ABL bulk similarity approach and those obtained by Monin-Obukhov similarity in the surface sublayer. Similarly, values of surface flux of sensible heat H determined by this method compared well (r = 0.90) with the regional means measured at six ground stations. The corresponding regional evaporation values, determined with the energy budget equation, also compared favorably (r = 0.94). 相似文献
8.
The characteristics of the boundary layer over complex terrain (Lannemezan - lat.: 43.7° N and, long.: 0.7 ° E) are analyzed for various scales, using measurements obtained during the COCAGNE Experiment. In this first part, the dynamic characteristics of the flow are studied with respect to atmospheric stability and the relief at small (~20 km) and medium scales (~100 km). These relief scales depend on the topographical profile of the Lannemezan Plateau along the dominant axis of the wind (E-W) and the Pyrénées Mountains located at the south of the experimental site. The terrain heterogeneities have a standard deviation of ~48 m and a wavelength of ~2 km.The averaged vertical profiles of wind speed and direction over the heterogeneous terrain are analyzed. The decrease of wind speed within the boundary layer is greater than over flat terrain (WANGARA Experiment). However, a comparison between ETTEX (complex terrain) and COCAGNE vertical wind speed profiles shows good agreement during unstable conditions. In contrast, during neutral conditions a more rapid increase with normalized height is found with COCAGNE than with ETTEX and WANGARA data. The vertical profiles of wind direction reveal an influence of the Pyrénées Mountains on the wind flow. The wind rotation in the BL is determined by the geostrophic wind direction-Pyrénées axis angle (negative deviation) as the geostrophic wind is connected with the Mountain axis.When the geostrophic wind does not interact with the Pyrénées axis, the mean and turbulent wind flow characteristics (drag coefficient C
D, friction velocity u
*) depend on the topography of the plateau. When the wind speed is strong (>6 m s -1), an internal boundary layer is generated from the leading edge of the Plateau. 相似文献
9.
More than 8000 10-min profiles of wind and temperature obtained during an extensive field experiment have been analyzed. The study was carried out in the environs of Valladolid (Spain) where a 100-m and a 6-m meteorological tower are located. Less than 20% of data were discarded due to equipment failure. Because of its exceptional flatness, the site is almost ideal for model performance comparisons.Predicted profiles of wind speed and potential temperature at 12, 26, 51, and 100 m heights were obtained using the methods proposed by Berkowicz and Prahm (1982) and San José (1983) based on values observed on a 6 m tower. Statistical t, F, and R tests were used to determine bias, scatter and correlation. The data were classified according to atmospheric stratification and height above ground. Finally, a determination was made of the predicted wind speeds and potential temperatures that fell within the 1 and 20% confidence ranges centered at the measured value. San José's method performed better than did that of Berkowicz and Prahm for the temperature profiles in both unstable and stable conditions. However, no significant differences were found for the wind speed profiles. 相似文献
10.
This paper deals with the derivation of the convective mixing height and the characteristic convective velocity w
* from profiles of
w
measured by sodar. The parameters were obtained by fitting an analytical profile to the observed data. Results were compared with values obtained by the meteorological preprocessor of a dispersion model and from noon radiosoundings. In addition, a Monte Carlo method was applied to study the influence of measurement errors. It turned out that it is inherently difficult to determine the depth of deep mixed layers from sodar measurements with a limited range, although the determination of w
* should be possible. However, a significant underestimation of
w
, and thus w
*, was found, which is probably due to disproportional sampling of updrafts and downdrafts. 相似文献
11.
Lutz Hasse 《Boundary-Layer Meteorology》1971,1(3):368-379
The deviation of the sea surface temperature from the water temperature below is calculated as a function of the heat flow through the air-sea interface, using wind tunnel determinations of the effective thermal diffusivity in a boundary layer. The influence ofQ, shortwave radiation, andH, latent and sensible heat transfer plus effective back radiation, and U, wind speed, can be described by:T
0 –T
w =C
1 ·H/U +C
2 ·Q/U. The calculated coefficients vary slightly with reference depth, Tables II and III. They are in good agreement with independent observations.On leave at Department of Oceanography, Oregon State University, Corvallis, Oregon in 1969–70. 相似文献
12.
The profile structure of wind speed and temperature in katabatic flow over a melting glacier is analyzed within the log-linear framework. Similarity between windspeed and temperature profiles is indicated but the log-linear model should be restricted to heights within 1.5 m of the ice. Marked deviation from the model occur at greater heights, probably due to the effects of flux divergence.Unlike results from other stable atmospheres, a decreases with increasing stability. This may arise from the use of the Obukhov length L. When the height H at which the wind speed reaches its maximum value is used instead, does not vary with stability. It has mean values of 4.5 and 4.3 for windspeed and temperature profiles, respectively. 相似文献
13.
14.
M. Segal 《Boundary-Layer Meteorology》1990,52(1-2):193-198
Calculations are made of the effects of thermal stability under a range of conditions, over the sea and land, on the physical factors (including the critical wind speed) affecting dust-storm generation, snow drift, and rough sea conditions. The computational procedure involves the surface friction velocity, u
*, and its relation with the aerodynamic roughness over aerodynamically rough, mobile surfaces. The results indicated that even at relatively high wind speeds, thermal effects under extreme advection situations may be significant, particularly for those properties of the agitated surface dependent on u
*
3 and u
*
4. 相似文献
15.
Abstract The relationships between monthly anomalies of sea surface temperature (SST) and monthly anomalies of several surface wind parameters are examined using ten years of data from the mid‐latitude North Pacific Ocean. The wind parameters involve both u3 * and curl τ, where u* is the atmospheric friction velocity and τ the surface stress. These quantities are calculated from surface wind components analysed on synoptic (6‐hourly) maps. In order to examine the effect of synoptic disturbances, the time series of surface wind components at each grid point is high‐pass filtered (passing periods less than 10 days) and the above wind parameters are calculated from both filtered and unfiltered wind components. Two statistically significant relationships are found between monthly anomalies of SST and those of the various wind parameters. The first is a large coherent negative correlation between monthly anomalies of u3 * calculated from the high‐pass filtered wind components and month‐to‐month changes in the SST anomalies in the Central Pacific. This relationship is attributed to the production of turbulent vertical mixing in the ocean by synoptic disturbances in the atmosphere. The second relationship is a large positive correlation between curl τ calculated from the unfiltered wind components and SST anomaly changes in the Eastern Pacific. This relationship, which is opposite to that expected from Ekman pumping, is attributed to a negative association between the wind stress curl and the meridional advection of heat by the eastern boundary current system. It is shown that these atmospheric forcing mechanisms explain up to 10 per cent of the variance of monthly SST anomalies in a large part of the mid‐latitude North Pacific Ocean. This amount is in addition to, but certainly less than, that which can be explained by anomalous horizontal advection through statistical relationships with sea‐level pressure anomalies (Davis, 1976). 相似文献
16.
A theory for the scalar roughness and the scalar transfer coefficients over snow and sea ice 总被引：1，自引：0，他引：1
Edgar L. Andreas 《Boundary-Layer Meteorology》1987,38(1-2):159-184
Although the bulk aerodynamic transfer coefficients for sensible (C
H
) and latent (C
E
) heat over snow and sea ice surfaces are necessary for accurately modeling the surface energy budget, they have been measured rarely. This paper, therefore, presents a theoretical model that predicts neutral-stability values of C
H
and C
E
as functions of the wind speed and a surface roughness parameter. The crux of the model is establishing the interfacial sublayer profiles of the scalars, temperature and water vapor, over aerodynamically smooth and rough surfaces on the basis of a surface-renewal model in which turbulent eddies continually scour the surface, transferring scalar contaminants across the interface by molecular diffusion. Matching these interfacial sublayer profiles with the semi-logarithmic inertial sublayer profiles yields the roughness lengths for temperature and water vapor. When coupled with a model for the drag coefficient over snow and sea ice based on actual measurements, these roughness lengths lead to the transfer coefficients. C
E
is always a few percent larger than CH. Both decrease monotonically with increasing wind speed for speeds above 1 m s–1, and both increase at all wind speeds as the surface gets rougher. Both, nevertheless, are almost always between 1.0 × 10–3 and 1.5 × 10–3. 相似文献
17.
Vertical profiles of the structure parameter of temperature C
infT
sup2
in the stable, nocturnal boundary layer (NBL) have been obtained with the analytic models described by Nieuwstadt (1984, 1985) and Sorbjan (1986) and the numerical model of Duynkerke and Driedonks (1987). These theoretical profiles are compared with observed profiles from the meteorological mast at Cabauw, The Netherlands. From the observations, it is found that C
infT
sup2
is large in the surface layer and small at the top of the NBL. Observations during nights with moderate geostrophic winds or during the first few hours of nights with a high geostrophic wind show a continuous decrease of C
infT
sup2
from the surface layer to the top of the NBL. Observations made later on nights with a high geostrophic wind show the development of a maximum of C
infT
sup2
at about three quarters of the NBL. From the comparison with the models, we conclude that the observed profiles are most satisfactorily described by the model of Duynkerke and Driedonks. 相似文献
18.
本文用大气边界层运动方程的数值积分研究了当边界层顶风向不变但风速变化时对大气边界层的内参数u_*/A(u_*为摩擦速度,A为上界风速)和α角(地面风与上界风向的交角)的影响。设上界处风速随时间指数增加及减少,最后趋于定常。在大气正、斜压时,u_*/A及α角的时间变化均是振幅衰减的振荡,最后趋于定常时相应的值。在时间变化过程中的任一时刻,内参数值与当上界条件取该时刻上界风时的定常解结果有一定的差别,严格说,定常时的内参数值并不能直接用于当上界风非定常时。本文还考虑了上界风速非定常对风廓线的影响。 相似文献
19.
A review is presented of some Russian-language papers published as early as 1952–1954 that are unknown to most English-speaking readers. In these papers the influence of an abrupt change in the surface friction velocityv
*, surface roughnessz
0 and surface temperature or heat flux on the wind velocity profile and vertical motions has been investigated analytically and numerically. Most of the theories are based on the exchange-coefficient approximation for momentum and heat. In terms of this approximation, further generalization and development of the problem is discussed.In an appendix, the Shwetz method for approximate solution of the boundary-layer partial differential equations is briefly described, using as an example an equation for which an exact solution is also possible. 相似文献
20.
Stably stratified flow in a marine atmospheric surface layer 总被引：3，自引：1，他引：2
Data from the marine atmospheric surface layer have been analysed. The data set consists of about two weeks with tower measurements up to 31 m of mean profiles of wind, temperature, and humidity, together with 20 Hz turbulence data. Mean wind, temperature, and humidity profiles up to 2000 m are also available from pibal trackings and radio soundings. Wave height was measured at 2 Hz, using an inverted echo-sounder.It was found from pibal wind profiles that low level jets were present during 2/3 of the measurements, having their maxima in the height interval 40 to 300 m. Here only data from the remaining 1/3 of the measurements, without low level jets, have been analysed.Non-dimensional wind and temperature gradients agree with results over homogeneous land surfaces as regards stability dependence during stable conditions that prevailed during this experiment. Linear regression gave
m
= 1 + 6.8z/L and
m
= 1 + 8.3z/L. No significant sea wave influence was found. The same was vrue for me dimensionless standard deviations of the three wind components, except for the vertical component. The expected wind speed dependence was found for the neutral drag coefficient, givingC
dN
= 0.109U + 0.33 at 10 m, and a dependence on the wave parameter,C/u
*, was confirmed. Note, however, that the data set was restricted to low and moderate wind speeds and that stratification was mainly stable.Power spectra, non-dimensionalized according to suface-layer theories, do not follow the expected stability dependence. It was shown that this may be a consequence of the presence of gravity waves in the stable marine boundary layer. Indicators of gravity waves were found in most runs. The TKE budget agrees with findings over homogeneous land areas. The pressure transport term was found to be a source of energy also for near neutral conditions. 相似文献