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1.
Analysis of Atmospheric Boundary Layer Height Characteristics over the Arctic Ocean Using the Aircraft and GPS Soundings 
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下载免费PDF全文 Utilizing aircraft sounding data collected from the Surface Heat Budget of the Arctic Ocean (SHEBA, 1998) campaign, the authors evaluated commonly-used profile methods for Arctic ABL height estimation by validating against the’true’ABL height from aircraft sounding profiles, where ABL height is defined as the top of the layer with significant turbulence. Furthermore, the best performing method was used to estimate ABL height from the one-year GPS soundings obtained during SHEBA (October 1997-October 1998). It was found that the temperature gradient method produces a reliable estimate of ABL height. Additionally, the authors determined optimal threshold values of temperature gradient for stable boundary layer (SBL) and convective boundary layer (CBL) to be 6.5 K/100 m and 1.0 K/100 m, respectively. The maximum ABL height during the year was 1150 m occurred in May. Median values of Arctic ABL height in May, June, July, and August were 400 m, 430 m, 180 m, and 320 m, respectively. Arctic ABL heights are clearly higher in the spring than in the summer. 相似文献
2.
Atmospheric Boundary-Layer Dynamics with Constant Bowen Ratio 总被引：1，自引：1，他引：0
Amilcare Porporato 《Boundary-Layer Meteorology》2009,132(2):227-240
Motivated by the observation that the diurnal evolution of sensible and latent heat fluxes tends to maintain a constant Bowen
ratio, we derive approximate solutions of the ordinary differential equations of a simplified atmospheric boundary-layer (ABL)
model. Neglecting the early morning transition, the potential temperature and specific humidity of the mixed layer are found
to be linearly related to the ABL height. Similar behaviour is followed by the inversion strengths of temperature and humidity
at the top of the ABL. The potential temperature of the mixed layer depends on the entrainment parameter and the free-atmosphere
temperature lapse rate, while the specific humidity also depends on the free-atmosphere humidity lapse rate and the Bowen
ratio. The temporal dynamics appear only implicitly in the evolution of the height of the boundary layer, which in turn depends
on the time-integrated surface sensible heat flux. Studying the limiting behaviour of the Bowen ratio for very low and very
large values of net available energy, we also show how the tendency to maintain constant Bowen ratio during midday hours stems
from its relative insensitivity to the atmospheric conditions for large values of net available energy. The analytical expression
for the diurnal evolution of the ABL obtained with constant Bowen ratio is simple and provides a benchmark for the results
of more complex models. 相似文献
3.
Summary The article brings together theoretical knowledge about the structure of the atmospheric boundary layer (ABL) which should be typical for smog situations and ABL features observed during two severe smog episodes. It can be shown that the convective boundary layer (CBL) as a special ABL type is very favourable for the occurrence of smog and that at first glance simple modelling of the CBL seems to recommend itself for forecasting purposes.However, the real smog situations show much more complexity, and even high reaching (up to 1500 m) stable boundary layers (SBL) occur. Simple modelling fails because important input parameters (such as vertical wind and advection terms) cannot be derived neither from measurements nor from meso-scale models in sufficient accuracy. Even the most advanced forecast models cannot describe the ABL structure correctly or in sufficient detail to estimate the development of a smog situation.With 19 Figures 相似文献
4.
A. K. Georgoulias D. K. Papanastasiou D. Melas V. Amiridis G. Alexandri 《Meteorology and Atmospheric Physics》2009,104(1-2):103-111
The atmospheric boundary layer (ABL) is characterized by the turbulence eddies that transport heat, momentum, gaseous constituents and particulate matter from Earth’s surface to the atmosphere and vice versa. Thus, the determination of its height has a great importance in a wide range of applications like air quality forecasting and management. This study aims at estimating the height of the ABL in a suburban environment and at investigating its temporal variation and its relationship with meteorological variables, like temperature and wind. For this purpose, radiosonde data from the suburban area of Thessaloniki, Greece, are analyzed. The data analysis reveals that ABL height is usually below 200 m in the morning hours during all seasons of the year and that is also low when near-surface temperature and wind speed are low too. Additionally, noon ABL height exhibits a strong seasonal variation, reaching higher values during summer than during winter.Very high values of ABL height, of the order of ~3,000 m, are occasionally observed in Thessaloniki during summer. Moreover, sea breeze development during summer is related to a slight reduction of the ABL height. 相似文献
5.
We discuss the structure and evolution of a cloud-free atmospheric boundary layer (ABL) during daytime over land, starting from a shallow ABL at sunrise and developing into a deep ABL with strong convection in the afternoon. The structure of the turbulence in the lower half of a convective ABL capped by an inversion is reasonably well understood. Less is known about the details of the turbulence in higher regions affected by entrainment, because of the difficulty in taking turbulence measurements there. For the evolution in time of the height of the ABL and its mean potential temperature mixed-layer models have been developed that give satisfactory agreement with observations. It has been shown that for many practical applications accurate knowledge of forcing functions and boundary conditions is more important than a refinement of the entrainment hypothesis. Observations show that the assumption of well-mixedness of first-order moments of conservative variables is not valid for all quantities. A simple similarity relation for the inclusion of the effect of entrainment on the shape of the vertical profiles is given. 相似文献
6.
The vertical and horizontal temperature structure of the atmospheric boundary layer (ABL) were studied using aircraft observations made in the lowest 2.4 km above ground level during the summer monsoon.The vertical temperature structure of the ABL in the region may be classified into the following four categories.Category The ABL consisted of two layers of thickness 700–900 m separated by a thin transition layer. The lapse rates in the former two layers were dry adiabatic.Category The lowest layer of the ABL of thickness 400–600 m was adiabatically stratified and the overlying layer was stable with gradients of potential temperature 4–5°C km–1. The stable layer contained a thin adiabatic stratified layer of 200–300 m thickness at a height of 1.5 km.Category The lowest 200–400 m layer of the ABL was adiabatically stratified and the overlying layer was stable with potential temperature gradients of 5–6 °C km1.Category The ABL was mainly stable with potential temperature gradients of 6 °C km–1 or greater. Occasionally thin layers with adiabatic stratification were found embedded in the ABL.The temperature distribution of the horizontal temperature at 900 m was mainly normal. The high-frequency portion of the spectra lying between 0.05 and 0.16 Hz (corresponding to wave length 1 km to 300 m) oscillated around the –\2/3 power law line. The spectral curve showed a significant peak at 0.011 Hz having a wave-length of 5 km.Department of Geoscience, North Carolina State University, Raleigh, NC, 27650, U.S.A. 相似文献
7.
A set of atmospheric general circulation model experiments were performed where the Community Atmospheric Model version 3.1 is forced with sea-surface temperatures (SSTs) that have the imprint of tropical instability waves (TIWs) of varying strengths. The presence of TIWs in the SSTs increased the variance in the large-scale circulation in the atmospheric boundary layer (ABL). The impact of TIWs in the SST anomalies is directly seen in enhanced mixing of the air temperature anomalies, thereby diffusing the air temperature gradients setup by the oceanic fronts throughout the ABL. The presence of TIWs transformed the diffusive-natured ABL to advection-dominated regime. This implies that within the ABL, the presence of TIWs leads to the enhanced interactions among the neighboring grid cells and prompts greater horizontal communications among atmospheric variables. However, the advection in the ABL due to the TIWs is not a linear function of increasing TIW strength. Unlike air temperature, zonal, and vertical velocity, the variance in the meridional velocity changes at the top of the ABL due to the momentum mixing across the ABL in the vertical direction. This causes the ABL to be more turbulent beyond seasonal time scales. This analysis also suggests that a simple parameterization is not sufficient to take the account of rectification effects on the atmospheric variables that are missing due to the lack of TIW representation in the coarse-resolution coupled general circulation models. 相似文献
8.
Volker K. Schilling 《Boundary-Layer Meteorology》1991,55(3):283-304
A parameterization scheme has been developed to describe the effects of a tall forest on the mean structure of the atmospheric boundary layer (ABL). The main advantage of the scheme is that dynamical and thermodynamical effects of a forest surface can be simulated satisfactorily using only a coarse-grid resolution within numerical models. Thereby, the canopy layer is parameterized as a quasi-subgrid phenomenon. This makes it possible to study meteorological phenomena within the ABL in a very economical way (with respect to computational time) whereby, nevertheless, more detailed information concerning the forest surface is taken into account than could be done using the same grid resolution and quite simple assumptions describing the canopy, e.g., the effective roughness.The applicability in numerical models is shown by using a slightly modified two-dimensional version of the mesoscale model FITNAH. For comparison, simulations with a high numerical grid resolution within the canopy have been carried out.Model results reproduce the known meteorological phenomena in forested areas, e.g., a stable thermal stratification near the surface during the day, and at night, a neutral — or slightly unstable condition — and, in general, reduced windspeed within the canopy layer.Diurnal variations and spatial distributions of temperature and humidity are found to be similar for both cases. Also, a thermally-induced local circulation system in the vicinity of a large clearing has been simulated satisfactorily.A comparison of the calculated results verifies that the parameterization scheme is quite suitable for simulating the effects of plant canopies on the distributions of meteorological variables in the ABL. 相似文献
9.
Simplified numerical models of the atmospheric boundary layer (ABL) are useful both for understanding the underlying dynamics and potentially providing parsimonious modelling approaches for inclusion in larger models. Herein the governing equations of a simplified slab model of the uniformly mixed, purely convective, diurnal ABL are shown to allow immediate solutions for the potential temperature and specific humidity as functions of the ABL height and net radiation when expressed in integral form. By employing a linearized saturation vapour relation, the height of the mixed layer is shown to obey a non-linear ordinary differential equation with quadratic dependence on ABL height. A perturbation solution provides general analytical approximations, of which the leading term is shown to represent the contribution under equilibrium evaporation. These solutions allow the diurnal evolution of the height, potential temperature, and specific humidity (i.e., also vapour pressure deficit) of the mixed layer to be expressed analytically for arbitrary radiative forcing functions. 相似文献
10.
复杂地形城市冬季边界层对气溶胶辐射效应的响应 总被引：9，自引：3，他引：6
作者着眼于城市气溶胶辐射效应与大气边界层的相互作用问题,针对地形复杂的兰州市及周边地区,开发应用了WRF(Weather Research and Forecasting,天气研究和预报)模式,使之与包含了大气气溶胶辐射效应和气溶胶粒子扩散的综合大气边界层数值模式嵌套起来.通过个例分析,揭示了冬季气溶胶辐射效应对边界层结构的定量影响.主要特征为夜间气溶胶的长波辐射效应使地面附近的气温增高,增温幅度为0.1～0.3 K/h,使低空(25～300 m)大气层冷却,降温幅度为0.08～0.15 K/h,风速在150 m以下减小;白天气溶胶的短波辐射效应使地面层内明显增温,1 h内升温约0.5 K,增温最大值在混合层顶500～600 m高度.受增温影响,垂直风场和水平风场随之调整,风速在450 m以下增大约0.1 m/s左右,而在450 m以上风速减小0.1 m/s左右. 相似文献
11.
The temperature and wind profiles in abaroclinic atmospheric boundary layer (ABL) are investigated.Assuming stationary conditions, the turbulent state in the ABL forstable and neutral conditions is uniquely determined by the Rossbynumber, the external stratification parameter and two externalbaroclinic parameters. A simple two-layer baroclinic model isdeveloped. It consists of a surface layer (SL) and overlyingEkman-type layer. The system of dynamic and heat transfer equations isclosed using K-theory. In the SL the turbulent exchangecoefficient is consistent with the results of similarity theorywhile in the Ekman layer it is assumed constant. The universalfunctions in the resistance, heat and humidity transfer laws arededuced from the analytical solutions for the wind and temperatureprofiles. The solutions of the ABL resistance laws for theinternal ABL parameters, necessary for the calculations of the ABLprofiles, are approximated in terms of the external ABLparameters. Favourable agreement of model results with theavailable experimental data is demonstrated. 相似文献
12.
In this paper we revise the similarity theory for the stably stratified atmospheric boundary layer (ABL), formulate analytical
approximations for the wind velocity and potential temperature profiles over the entire ABL, validate them against large-eddy
simulation and observational data, and develop an improved surface flux calculation technique for use in operational models. 相似文献
13.
A case study of warm air advection over the Arctic marginalsea-ice zone is presented, based on aircraft observations with direct flux measurements carriedout in early spring, 1998. A shallow atmospheric boundary layer (ABL) was observed, which wasgradually cooling with distance downwind of the ice edge. This process was mainly connected with astrong stable stratification and downward turbulent heat fluxes of about 10–20 W m-2, but wasalso due to radiative cooling. Two mesoscale models, one hydrostatic and the other non-hydrostatic,having different turbulence closures, were applied. Despite these fundamental differences betweenthe models, the results of both agreed well with the observed data. Various closure assumptions had amore crucial influence on the results than the differences between the models.Such an assumption was, for example,the parameterization of the surface roughness for momentum (z0) and heat (zT). This stronglyaffected the wind and temperature fields not only close to the surface but also within and abovethe temperature inversion layer. The best results were achieved using a formulation for z0 that took intoaccount the form drag effect of sea-ice ridges together withzT = 0.1z0. The stability within theelevated inversion strongly depended on the minimum eddy diffusivity Kmin. A simple ad hocparameterization seems applicable, where Kmin is calculated as 0.005 timesthe neutral eddy diffusivity. Although the longwave radiative cooling was largest within the ABL, theapplication of a radiation scheme was less important there than above the ABL. This was related to theinteraction of the turbulent and radiative fluxes. To reproduce the strong inversion, it wasnecessary to use vertical and horizontal resolutions higher than those applied in most regional andlarge-scale atmospheric models. 相似文献
14.
Determining Boundary-Layer Height from Aircraft Measurements 总被引：1，自引：0，他引：1
C. Dai Q. Wang J. A. Kalogiros D. H. Lenschow Z. Gao M. Zhou 《Boundary-Layer Meteorology》2014,152(3):277-302
The height of the atmospheric boundary layer (ABL) is an important variable in both observational studies and model simulations. The most commonly used measurement for obtaining ABL height is a rawinsonde profile. Mesoscale or regional scale models use a bulk Richardson number based on profiles of the forecast variables. Here we evaluate the limitations of several frequently-used approaches for defining ABL height from a single profile, and identify the optimal threshold value for each method if profiles are the only available measurements. Aircraft measurements from five field projects are used, representing a variety of ABL conditions including stable, convective, and cloud-topped boundary layers over different underlying surfaces. ABL heights detected from these methods were validated against the ‘true’ value determined from aircraft soundings, where ABL height is defined as the top of the layer with significant turbulence. A detection rate was defined to denote how often the ABL height was correctly diagnosed with a particular method. The results suggest that the temperature gradient method provides the most reasonable estimates, although the detection rate and suitable detection criteria vary for different types of ABL. The Richardson number method, on the other hand, is in most cases inadequate or inferior to the other methods that were tried. The optimal range of the detection criteria is given for all ABL types examined in this study. 相似文献
15.
Hrvoje Kozmar 《Theoretical and Applied Climatology》2011,106(1-2):95-104
The boundary layer wind tunnel at the Technische Universit?t München was tested for atmospheric boundary layer (ABL) simulations. The ABLs developing above rural, suburban, and urban terrains were reproduced using the Counihan method, i.e., castellated barrier wall, vortex generators, and a fetch of surface roughness elements. A series of flow-characteristic evaluations was performed to investigate the flow development and uniformity. Experimental results presented as mean velocity, turbulence intensity, integral length scale of turbulence, Reynolds stress, and power spectral density of velocity fluctuations were compared with the ESDU data and/or theoretical models. Generated ABL wind-tunnel simulations compare well with the rural, suburban, and urban ABLs. In the test section area used for experiments on structural models, the ABL simulation is developed and uniform. Results of this study indicate the boundary layer wind tunnel at the Technische Universit?t München can be successfully employed in a broad spectrum of engineering, environmental, and micrometeorological studies, where it is required to accurately reproduce ABL characteristics. 相似文献
16.
Atmospheric boundary-layer structure observed during a haze event due to forest-fire smoke 总被引：1，自引：0，他引：1
During a haze event in Baltimore, U.S.A. from July 6 to 8, 2002, smoke from forest fires in the Québec region (Canada), degraded air quality and impacted upon local climate, decreasing solar radiation and air temperature. The smoke particles in and above the atmospheric boundary layer (ABL) served as a tracer and provided a unique opportunity to investigate the ABL structure, especially entrainment. Elastic backscatter lidar measurements taken during the haze event distinctly reveal the downward sweeps (or wisps) of smoke-laden air from the free atmosphere into the ABL. Visualisations of mechanisms such as dry convection, the entrainment process, detrainment, coherent entrainment structures, and mixing inside the ABL, are presented. Thermals overshooting at the ABL top are shown to create disturbances in the form of gravity waves in the free atmosphere aloft, as evidenced by a corresponding ripple structure at the bottom of the smoke layer. Lidar data, aerosol ground-based measurements and supporting meteorological data are used to link free atmosphere, mixed-layer and ground-level aerosols. During the peak period of the haze event (July 7, 2002), the correlation between time series of elastic backscatter lidar data within the mixed layer and the scattering coefficient from a nephelometer at ground level was found to be high (R=0.96 for z =324 m, and R=0.89 for z=504 m). Ground-level aerosol concentration was at a maximum about 2 h after the smoke layer intersected with the growing ABL, confirming that the wisps do not initially reach the ground. 相似文献
17.
Ankur R. Desai Kenneth J. Davis Christoph J. Senff Syed Ismail Edward V. Browell David R. Stauffer Brian P. Reen 《Boundary-Layer Meteorology》2006,119(2):195-238
The atmospheric boundary-layer (ABL) depth was observed by airborne lidar and balloon soundings during the Southern Great Plains 1997 field study (SGP97). This paper is Part I of a two-part case study examining the relationship of surface heterogeneity to observed ABL structure. Part I focuses on observations. During two days (12–13 July 1997) following rain, midday convective ABL depth varied by as much as 1.5 km across 400 km, even with moderate winds. Variability in ABL depth was driven primarily by the spatial variation in surface buoyancy flux as measured from short towers and aircraft within the SGP97 domain. Strong correlation was found between time-integrated buoyancy flux and airborne remotely sensed surface soil moisture for the two case-study days, but only a weak correlation was found between surface energy fluxes and vegetation greenness as measured by satellite. A simple prognostic one-dimensional ABL model was applied to test to what extent the soil moisture spatial heterogeneity explained the variation in north–south ABL depth across the SGP97 domain. The model was able to better predict mean ABL depth and variations on horizontal scales of approximately 100 km using observed soil moisture instead of constant soil moisture. Subsidence, advection, convergence/divergence and spatial variability of temperature inversion strength also contributed to ABL depth variations. In Part II, assimilation of high-resolution soil moisture into a three-dimensional mesoscale model (MM5) is discussed and shown to improve predictions of ABL structure. These results have implications for ABL models and the influence of soil moisture on mesoscale meteorology 相似文献
18.
The atmospheric boundary layer (ABL) model of Weng and Taylor with E−ℓ turbulence closure is applied to simulate the one-dimensional stably stratified ABL. The model has been run for nine hours from specified initial wind, potential temperature and turbulent kinetic energy profiles, and with a specified cooling rate applied at the surface. Different runs are conducted for different cooling rates, geostrophic winds and surface roughnesses. The results are discussed and compared with other models, large-eddy simulations and published field data. 相似文献
19.
Xiaolan Li Yangfeng Wang Lidu Shen Hongsheng Zhang Hujia Zhao Yunhai Zhang Yanjun Ma 《Acta Meteorologica Sinica》2018,32(2):302-312
The characteristics of boundary layer structure during a persistent regional haze event over the central Liaoning city cluster of Northeast China from 16 to 21 December 2016 were investigated based on the measurements of particulate matter (PM) concentration and the meteorological data within the atmospheric boundary layer (ABL). During the observational period, the maximum hourly mean PM2.5 and PM10 concentrations in Shenyang, Anshan, Fushun, and Benxi ranged from 276 to 355 μg m–3 and from 378 to 442 μg m–3, respectively, and the lowest hourly mean atmospheric visibility (VIS) in different cities ranged from 0.14 to 0.64 km. The central Liaoning city cluster was located in the front of a slowly moving high pressure and was mainly controlled by southerly winds. Wind speed (WS) within the ABL (< 2 km) decreased significantly and WS at 10-m height mostly remained below 2 m s–1 during the hazy episodes, which was favorable for the accumulation of air pollutants. A potential temperature inversion layer existed throughout the entire ABL during the earlier hazy episode [from 0500 Local Time (LT) 18 December to 1100 LT 19 December], and then a potential temperature inversion layer developed with the bottom gradually decreased from 900 m to 300 m. Such a stable atmospheric stratification further weakened pollutant dispersion. The atmospheric boundary layer height (ABLH) estimated based on potential temperature profiles was mostly lower than 400 m and varied oppositely with PM2.5 in Shenyang. In summary, weak winds due to calm synoptic conditions, strong thermal inversion layer, and shallow atmospheric boundary layer contributed to the formation and development of this haze event. The backward trajectory analysis revealed the sources of air masses and explained the different characteristics of the haze episodes in the four cities. 相似文献
20.
黑河绿洲区不均匀下垫面大气边界层结构的大涡模拟研究 总被引：11，自引：4，他引：7
采用RAMS模式中大涡模拟的方法,加入高分辨率的植被和土壤资料,模拟了黑河（张掖地区）不均匀下垫面条件下大气边界层演变过程。分析了模拟的地表通量、边界层的平均结构和湍流二阶量,并用黑河试验的观测资料检验了模式的模拟性能。结果表明,模拟的平均结构较好地展现了不均匀下垫面条件下边界层内从稳定层结到混合层发展,夹卷层形成,底层逆温层出现,混合层过渡到残留层等的演变过程,呈现出了从初始的稳定边界层发展到对流边界层,最后又形成夜问稳定边界层的日变化规律。湍流二阶量的分析显示,在非均匀下垫面条件下边界层内湍流二阶量的垂直分布与边界层的发展相对应,白天湍流二阶量出现两个峰值,分别位于近地层和混合层顶。与观测资料和现有研究的对比表明,RAMS中陆面模块（LEAF）地表参数不能较好地反映黑河地区的植被特征,模拟的白天地表感热和潜热通量偏小,气温白天偏低、夜间偏高,相对湿度也有偏差。 相似文献