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1.
Mohamed S. Smeda 《Boundary-Layer Meteorology》1979,16(2):115-129
A study has been made of the evolution of the planetary boundary layer height (PBLH), the heat flux, and momentum flux using
Clarke's Wangara data for a period of two days and two nights, 33/34–34/35. The observed Wangara data are considered as being
an output of the first two internal levels of a general circulation model, at 1000 and 2000 m height.
A time-dependent equation has been used to forecast, explicitly, the PBLH for both convectively unstable and stable periods.
A comparison is made between observed and computed values whenever possible.
In the unstable case, the Deardorff model (1974) has been used for the prediction of the unstable PBLH. Part of the stable
case study involved a formulation of a time-dependent model for the prediction of the stable PBLH. The solution obtained from
the model compared favourably with the results of a model suggested by Khakimov.
Contribution number 382. 相似文献
2.
3.
An improved non-stationary two-layer model is presented for the simulation of wind speed maxima in the nocturnal boundary
layer. The model is based on the idea of Blackadar (1957), who proposed as forcing mechanism an inertial oscillation of the
ageostrophic component of the wind vector in the levels above the top of the nocturnal radiation inversion. First, the time-dependent
variation of the nocturnal boundary-layer height is studied by means of prognostic equations; there is a good agreement between
observed and calculated height data for three days of the Wangara experiment. Furthermore, a diurnal variation of the drag
coefficient is considered in the lower layer by decreasing the coefficient by a factor of 10–20 due to stabilization of this
layer during the night. The marked temporal decrease (increase) of the drag coefficient in the first hours after sunset (sunrise)
is described by a function
. The incorporation of these two effects into the model gives results which are in good agreement with observed wind data
for Wangara days 13/14, 30/31, and 33/34. 相似文献
4.
5.
Radiative aerosols are known to influence the surface energy budget and hence the evolution of the planetary boundary layer. In this study, we develop a method to estimate the aerosol-induced reduction in the planetary boundary layer height(PBLH) based on two years of ground-based measurements at a site, the Station for Observing Regional Processes of the Earth System(SORPES), at Nanjing University, China, and radiosonde data from the meteorological station of Nanjing. The observations show that increased aerosol loads lead to a mean decrease of 67.1 W m-2for downward shortwave radiation(DSR) and a mean increase of 19.2 W m-2for downward longwave radiation(DLR), as well as a mean decrease of 9.6W m-2for the surface sensible heat flux(SHF) in the daytime. The relative variations of DSR, DLR and SHF are shown as a function of the increment of column mass concentration of particulate matter(PM2.5). High aerosol loading can significantly increase the atmospheric stability in the planetary boundary layer during both daytime and nighttime. Based on the statistical relationship between SHF and PM2.5column mass concentrations, the SHF under clean atmospheric conditions(same as the background days) is derived. In this case, the derived SHF, together with observed SHF, are then used to estimate changes in the PBLH related to aerosols. Our results suggest that the PBLH decreases more rapidly with increasing aerosol loading at high aerosol loading. When the daytime mean column mass concentration of PM2.5reaches 200 mg m-2, the decrease in the PBLH at 1600 LST(local standard time) is about 450 m. 相似文献
6.
In this paper,mixed layer height and certain mean elements are predicted by using a dry mixed layer model.Their variation with time and some basic properties are discussed.The model is tested with the 1967 Australian Wangara experimental data.Comparison of the calculated results with the observed data is conducted.The aim of this paper is to build a predictive model describing the basic properties of the mixed layer and attempts to formulate a boundary layer parameterization scheme suitable for the numerical weather prediction model. 相似文献
7.
大气边界层高度是天气、气候、大气环境研究中的一个重要参数,目前尚缺少基于激光雷达探测系统反演全天边界层高度的有效方法。文中利用北京朝阳站、大兴站的激光云高仪数据,首先评估了梯度法、标准偏差法、曲线拟合法和小波协方差法反演边界层高度的适用性和局限性,发现梯度法容易受环境噪声的影响,曲线拟合法稳定性较好,但在夜间弱湍流条件下会将残留层高度误判为夜间边界层高度。提出两步曲线拟合法,将一天中边界层结构划分为白天的对流边界层、夜间的残留层和稳定边界层,通过用不同的理想曲线对其进行两步拟合,获取全天边界层高度的变化。将两步曲线拟合法的反演结果与基于L波段探空雷达的位温梯度法的探测结果进行比较发现:两者相关系数为0.91,证明了两步曲线拟合法的可行性以及激光云高仪探测边界层高度的应用潜力。采用该方法反演2017年5—6月朝阳站与大兴站边界层高度,对比发现:城区特殊的下垫面性质使朝阳站日间对流边界层发展更早,边界层高度更高,全天朝阳站边界层高度的变化在308—1391 m,大兴站在197—1302 m。 相似文献
8.
The planetary boundary layer height (PBLH) was calculated using the radiosonde sounding data, including 120 L-band operational sites and 8 GPS sites in China. The diurnal and seasonal variations of PBLH were analyzed using radiosonde sounding (OBS-PBLH) and ERA data (ERA-PBLH). Based on comparison and error analyses, we discussed the main error sources in these data. The frequency distributions of PBLH variations under different regimes (the convective boundary layer, the neutral residual layer, and the stable boundary layer) can be well fitted by a Gamma distribution and the shape parameter k and scale parameter s values were obtained for different regions of China. The variation characteristics of PBLH were found in summer under these three regimes for different regions. The relationships between PBLH and PM2.5 concentration generally follow a power law under very low or no precipitation conditions in the region of Beijing, Tianjin and Hebei in summer. The results usually deviated from this power distribution only under strong precipitation or high relative humidity conditions because of the effects of hygroscopic growth of aerosols or wet deposition. The OBS-PBLH provided a reasonable spatial distribution relative to ERA-PBLH. This indicates that OBS-PBLH has the potential for identifying the variation of PM2.5 concentration. 相似文献
9.
北京城市通量足迹及源区分布特征分析 总被引：2，自引：1，他引：1
城市下垫面具有不同于其他下垫面的特殊复杂性,通量的源汇分布十分不均,导致直接测量以及定量的描述城市中水汽、二氧化碳等通量变得非常困难。涡动观测系统在城市通量观测中得到广泛应用,但由于涡动协方差观测系统传感器都架设在一定的高度上,其测量结果只反映特定点下垫面或某部分下垫面的物理过程,不能说明观测结果是否具有下垫面属性的代表性,无法反映观测通量的空间变异性。足迹函数(Footprint)的产生就是为了解决这一问题,其又称源权重函数,是描述近地面层表面源或汇的空间分布和仪器观测通量值之间关系的函数。本文采用北京325 m气象塔近1年7层涡动协方差观测数据、超声数据,分析了不同风向、不同稳定度、不同高度下足迹函数所表达的通量贡献区域范围的变化规律。结果表明,在大气稳定条件下时,通量贡献区范围的大小与主风向无显著差异,而不稳定条件下计算结果与主风向无关。在不同高度下所有稳定条件下通量贡献区范围要大于不稳定条件,中性条件则介于两者之间。8 m、16 m高度上的观测结果不能完全代表城市下垫面通量贡献区,47 m以上能够代表城市下垫面通量贡献区,280 m则已经包含了郊区和城区的权重平均。同一大气稳定度条件下,高度越高通量贡献区范围越大,90%通量贡献区范围与观测高度成线性关系,这种线性关系可以预测没有观测高度或者更高处的通量贡献区范围。 相似文献
10.
Planetary boundary layer height (PBLH) is an important input parameter for any boundary layer study or model, either climate or atmospheric. The variation of the PBLH is also of great significance to the physical processes of numerical prediction, diagnosis of weather forecasting and monitoring urban pollutants. However, effective ways to monitor the PBLH continuously are lack. Wind profilers are commonly used in monitoring PBLH continuously because of its high temporal and spatial resolution, coupled with capability of continuous detection. In this paper, the covariance wavelet transform (CWT) is used to analyze the range-corrected signal-to-noise ratio (SNR) of the wind profiler to determine the PBLH, which is then compared with the results measured by the gradient method and the radiosonde. The conclusions are as follows: (1) The scaling parameter a and translation parameter b of the wavelet are critical in determination of the PBLH by applying the CWT as different values may get completely different results, which requires to select appropriate values in the calculation carefully. (2) Quality control is crucial in determining the PBLH because good quality control can help remove mutation points, which makes the determined PBLH more consistent with the actual situation. (3) In clear-air, the gradient method is not applicable if the boundary layer turbulence is inhomogeneous and the impact of noise is large for that it is easy to be impacted by the mutation of SNR caused by the atmosphere turbulence instability and other factors, which will cause large errors, while the CWT method as an improvement of the gradient method can determine the PBLH quite well. (4) Through quality control, the PBLHs determined by the CWT are consistent with those of radiosonde, and the correlation coefficient between them is 0.87. 相似文献
11.
The impact of the Wangara experiment 总被引：1，自引：0，他引：1
12.
13.
非均匀网格的过渡湍流理论及其在大气边界层数值模拟中的应用 总被引：1，自引：1，他引：1
本文将Stull提出的均匀网格下的过渡湍流理论推广到非均匀网格情形，推广的非均匀网格的过渡湍流理论满足Stull提出的对过渡矩阵系数的要求并具有清晰的物理意义。然后，将非均匀网格的过渡湍流理论应用于一维大气边界层数值模式中，对Wangara资料进行了模拟，并与均匀网格情形进行了对比。计算表明，非均匀网格的过渡湍流模式能很好地模拟Wangara大气边界层平均量与湍流量的变化；本文非均匀网格的过渡湍流理论的推广是可行的，它可能会在大气边界层数值模拟及其他方面（如：中尺度模式）得到应用。 相似文献
14.
A model of the evolution of the nocturnal stable boundary layer height, based on the heat conservation equation for a turbulent flow, is presented. This model is valid for nights with weak winds and little cloudiness in rural areas. The model includes an expression of vertical profile of potential temperature within the boundary layer, which is obtained using micrometeorological information from Prairie Grass, Wangara and O'Neill Projects. The expression turned out to be a second-grade polynomial of the dimensionless height of the nocturnal stable boundary layer. The resulting model is a function of the Monin–Obukhov length, the surface potential temperature of air and the roughness length. This model was satisfactorily compared with micrometeorological data. It was applied at three stations of Argentina, using surface hourly meteorological information. From the results that were obtained, the monthly average values of the stable boundary layer thickness were analysed. The maximum monthly average values occur during the cold season and the minimum ones take place during the hot season. It was observed that the monthly average thickness increases with latitude. 相似文献
15.
Wavelet analysis was applied to lidar observations to retrieve the planetary boundary layer height(PBLH)over Guangzhou from September 2013 to November 2014 over Guangzhou. Impact of the boundary effect and the wavelet scale factor on the accuracy of the retrieved PBLH has been explored thoroughly. In addition, the PBLH diurnal variations and the relationship between PM_(2.5) concentration and PBLH during polluted and clean episodes were studied. Results indicate that the most steady retrieved PBLH can be obtained when scale factor is chosen between 300-390 m. The retrieved maximum and minimum PBLH in the annual mean diurnal cycle were ～1100 m and ～650 m, respectively. The PBLH was significantly lower in the dry season than in the wet season, with the average highest PBLH in the dry season and the wet season being ～1050 m and ～1200 m respectively. Compared to the wet season, the development of PBLH in the dry season was delayed by at least one hour due to the seasonal cycle of solar radiation. Episode analysis indicated that the PBLH was ～50% higher during clean episodes than during haze episodes. The average highest PBLH in the haze episodes and clean episodes were ～800 m and ～1300 m,respectively. A significant negative correlation between PBLH and PM_(2.5) concentration(r =-0.55**) is discovered.According to China"Ambient Air Quality Standard", the PBLH values in good and slightly polluted conditions were 1/6-1/3 lower than that in excellent conditions, while the corresponding PM_(2.5) concentration were ～2-2.5 times higher. 相似文献
16.
Yidan SI Shenshen LI Liangfu CHEN Chao YU Zifeng WANG Yang WANG Hongmei WANG 《大气科学进展》2018,35(4):479-492
Few studies have specifically focused on the validation and spatiotemporal distribution of planetary boundary layer height(PBLH) and relative humidity(RH) data in China. In this analysis, continuous PBLH and surface-level RH data simulated from GEOS-5 between 2004 and 2012, were validated against ground-based observations. Overall, the simulated RH was consistent with the statistical data from meteorological stations, with a correlation coefficient of 0.78 and a slope of 0.9. However, the simulated PBLH was underestimated compared to LIDAR data by a factor of approximately two,which was primarily because of poor simulation in late summer and early autumn. We further examined the spatiotemporal distribution characteristics of two factors in four regions—North China, South China, Northwest China, and the Tibetan Plateau. The results showed that the annual PBLH trends in all regions were fairly moderate but sensitive to solar radiation and precipitation, which explains why the PBLH values were ranked in order from largest to smallest as follows: Tibetan Plateau, Northwest China, North China, and South China. Strong seasonal variation of the PBLH exhibited high values in summer and low values in winter, which was also consistent with the turbulent vertical exchange. Not surprisingly, the highest RH in South China and the lowest RH in desert areas of Northwest China(less than 30%). Seasonally, South China exhibited little variation, whereas Northwest China exhibited its highest humidity in winter and lowest humidity in spring,the maximum values in the other regions were obtained from July to September. 相似文献
17.
Observations from the Horizontal Array Turbulence Study (HATS) field program are used to examine the attenuation of measured
scalar fluxes caused by spatial separation between the vertical velocity and scalar sensors. The HATS data show that flux
attenuation for streamwise, crosswind, and vertical sensor displacements are each a function of a dimensionless, stability-dependent
parameter n
m
multiplied by the ratio of sensor displacement to measurement height. The scalar flux decays more rapidly with crosswind
displacements than for streamwise displacements and decays more rapidly for stable stratification than for unstable stratification.
The cospectral flux attenuation model of Kristensen et al. agrees well with the HATS data for streamwise sensor displacements,
although it is necessary to include a neglected quadrature spectrum term to explain the observation that flux attenuation
is often less with the scalar sensor downwind of the anemometer than for the opposite configuration. A simpler exponential
decay model provides good estimates for crosswind sensor displacements, as well as for streamwise sensor displacements with
stable stratification. A model similar to that of Lee and Black correctly predicts flux attenuation for a combination of streamwise
and crosswind displacements, i.e. as a function of wind direction relative to the sensor displacement. The HATS data for vertical
sensor displacements extend the near-neutral results of Kristensen et al. to diabatic stratification and confirm their finding
that flux attenuation is less with the scalar sensor located below the anemometer than if the scalar sensor is displaced an
equal distance either horizontally or above the anemometer. 相似文献
18.
L. Mahrt Dean Vickers Jim Edson James M. Wilczak Jeff Hare Jørgen Højstrup 《Boundary-Layer Meteorology》2001,100(1):47-61
The adjustment of the boundary layer immediately downstream froma coastline is examined based on two levels of eddy correlation data collected on a mast at the shore and six levels of eddy correlation data and profiles of mean variables collected from a mast 2 km offshore during the Risø Air-Sea Experiment. The characteristics of offshore flow are studied in terms of case studies and inter-variable relationships for the entire one-month data set. A turbulent kinetic energy budget is constructed for each case study.The buoyancy generation of turbulence is small compared to shear generation and dissipation. However, weakly stable and weakly unstable cases exhibit completely different vertical structure. With flow of warm air from land over cooler water, modest buoyancy destruction of turbulence and reduced shear generation of turbulence over the less rough sea surface cause the turbulence to rapidly weaken downstream from the coast. The reduction of downward mixing of momentum by the stratification leads to smaller roughness lengths compared to the unstable case. Shear generation at higher levels and advection of stronger turbulence from land often lead to an increase of stress and turbulence energy with height and downward transport of turbulence energy toward the surface.With flow of cool air over a warmer sea surface, a convective internal boundary layer develops downstream from the coast. An overlying relatively thick layer of downward buoyancy flux (virtual temperature flux) is sometimes maintained by shear generation in the accelerating offshore flow. 相似文献
19.
A new empirical assessment of the functions A and B of Rossby-number similarity theory is made based on the Wangara data. Variations of these functions with stability, baroclinicity and time of day are discussed. It is found that B is dependent on stability in agreement with older data but contradicting the prediction of Csanady (1972). Coefficients expressing the variation of A and B with the two components of baroclinicity have been derived from the data, and these are claimed to be correct in regard to sign and approximately in regard to magnitude. Longer period time changes, represented by the diurnal cycle, are shown to result in systematic differences in A and B between the case of increasing stability and that of decreasing stability, for the same value of the stability parameter.The first attempt, to our knowledge, to present the actual functional form of the wind departure components (based on field data) is made. As the surface layer is approached in near-neutral conditions, the departure component in the direction of the surface wind assumes the expected logarithmic form. 相似文献
20.
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