我国草原下垫面低层大气湍流结构   总被引：3，自引：1，他引：3  

刘树华  刘和平  洪钟祥  李军  刘辉志  那景阳  吴志明 《大气科学》1996,20(3):378-383

利用超声风速仪资料分析了科尔沁草原下垫面低层大气的湍流谱结构，无量纲化湍流速度分量及温度脉动的标准偏差，和湍流通量与稳定度参数的关系。结果表明，草原下垫面低层大气湍流速度谱，在较宽的稳定度范围内， 符合Kolmogorov 相似理论，在惯性副区接近局地各向同性，无量纲化湍流速度分量及温度脉动的标准偏差服从A(1-Bζ)1/3和A(-ζ)-1/3规律， 湍流热通量与稳定度参数ζ存在较好的相关性。  相似文献   

ESTIMATES OF SEA SURFACE FLUXES DURING TOGA-COARE IOP     

Yao Huadong  Li Ji  Ding Yihui 《Acta Meteorologica Sinica》1996,10(2):175-192

With the marine ship observation data set obtained by three cruise-phases of Chinese Xi-angyanghong 5 from November 5,1992 to February 19,1993 in the TOGA-COARE IOP at 2°S,156°E.the sea surface fluxes at this point are estimated by three different bulk schemes.Firstly.aquasi-linear relation is found between the neutral drag coefficients and wind speed.Then,the sta-bility-dependent drag and heat transfer coefficients are solved in the iterative method.Based onthus-derived transfer coefficients,the momentum,sensible and latent heat fluxes are calculated.In the warm pool region,the fluxes corresponding to the westeily winds are much greater thanthose of the easterly trade winds.The magnitude of sea surface fluxes depends upon the atmo-spheric stability as well,in particular in the case of weak wind condition.The estimated sea sur-face net heat budget shows that considerable amount of heat transport from ocean to atmosphere ismainly produced by the effective longwave radiation,latent and sensible heat fluxes.Among themthe value of latent heat flux is the largest and the sensible heat flux is the smallest.Finally,an ac-curacy analysis is made by direct measurements with the eddy-correlation method on the JapaneseR/V Hakuho board at the same time.It is shown that the bulk-derived fluxes are acceptable withmuch confidence.The estimated effective longwave radiation is used to compare with those by di-rect observations on Xiangyanghong 5.This research is compared with TOGA investigation in thetropical western Pacific.  相似文献   

钱塘江江心排污的数值模拟   总被引：2，自引：0，他引：2       下载免费PDF全文

毛献忠  韩曾萃 《水科学进展》1996,7(3):200-206

从立面二维非恒定流体动力学方程出发,应用κ-ε湍流模式计算流场,再用准三维的浓度对流-扩散方程,即考虑了侧向扩散的立面二维浓度控制方程,模拟了钱塘江江心6个竖管排污在潮流作用下近区浓度场,其结果和实际观测值基本吻合。  相似文献   

Estimation of drag coefficient over the western desert sector of the Indian summer monsoon trough     

U C Mohanty  P S Parihar  T Venugopal  Parashuram 《Journal of Earth System Science》1995,104(2):273-287

In the estimation of momentum fluxes over land surfaces by the bulk aerodynamic method, no unique value of the drag coefficient (C _D) is found in the literature. The drag coefficient is generally estimated from special observations at different parts of the world. In this study an attempt is made to estimate drag coefficient over the western desert sector of India using data sets of Monsoon Trough Boundary Layer Experiment (MONTBLEX) during the summer monsoon season of 1990. For this purpose, the fast and slow response data sets obtained simultaneously from a 30 m high micro-meteorological tower at Jodhpur are used. All the observations used in this study are confined to a wind speed regime of 2.5–9.0 ms⁻¹. A comparison of momentum fluxes computed by eddy correlation (direct estimation) with profile and bulk aerodynamic (C _D = 3.9 × 10⁻³, Garratt, 1977) methods revealed that though the nature of variation of the fluxes by all these methods is almost similar, both the indirect methods give an under-estimated value of the fluxes. The drag coefficient is estimated as a function of wind speed and surface stability by a multiple regression approach. An average value of the estimated drag coefficient is found to be of the order of 5.43 × 10⁻³. The estimated value ofC _D is validated with a set of independent observations and found to be quite satisfactory. The recomputed momentum fluxes by bulk aerodynamic method using the estimated drag coefficient are in close agreement with the directly estimated fluxes.  相似文献   

Estimation of abl Parameters Using the Vertical Velocity Measurements of an Acoustic Sounder   总被引：2，自引：0，他引：2  

J. A. Kalogiros  C. G. Helmis  D. N. Asimakopoulos  P. G. Papageorgas 《Boundary-Layer Meteorology》1999,91(3):413-449

The friction velocity, the surface heat flux and the height of the Atmospheric Boundary Layer (ABL) are important parameters. In this work, vertical velocity variance ( _w ² ) and wind velocity structure parameter (C _v ² ) profiles estimated by acoustic sounder measurements are used, along with similarity relations, to estimate these parameters in the unstable Atmospheric Boundary Layer and the friction velocity in the stable one. The data were collected by two acoustic sounders with different height range and resolution under various atmospheric conditions (stability) and at two experimental sites in different terrain. The C _v ² profiles are estimated using gate difference of the vertical velocity measurements and the assumption of local isotropy. The vertical velocity data are corrected for the significant effects of noisy measurements and sampling volume averaging on the _w ² and C _v ² estimations using original techniques that are presented in this work. The results of the similarity method using acoustic sounder data are compared against estimates of the corresponding atmospheric parameters obtained from direct measurements. The comparison confirms the ability of the method to provide reasonably accurate estimates of these parameters especially in the middle of the day.  相似文献   

青藏高原地区能量水分循环：地表能量平衡和湍流热通量   总被引：2，自引：0，他引：2  

苏中波  张廷  马耀明  贾立  文军 《地球科学进展》2006,21(12):1224-1236

文章给出了青藏高原能量水分循环研究的概况和总结，着重估计了能量平衡各分项和湍流热通量等。在能量平衡的计算基础上，尽管能量不平衡的原因解释仍有争论并且没有解决，但我们揭示了GAME/Tibet试验观测资料中能量不平衡现象。我们发现估算的潜热通量比实际观测的要高许多。然而，根据能量平衡假设的计算结果和SEBS的估算一致性很好。在此基础上可以归纳出差异主要由GAME/Tibet试验观测资料中能量不平衡引起，潜热通量的实际观测可能偏小。  相似文献   

Modeling studies of the upper ocean response to a tropical cyclone     

Steven L. Morey  Mark A. Bourassa  Dmitry S. Dukhovskoy  James J. O’Brien 《Ocean Dynamics》2006,56(5-6):594-606

A coupled ocean and boundary layer flux numerical modeling system is used to study the upper ocean response to surface heat and momentum fluxes associated with a major hurricane, namely, Hurricane Dennis (July 2005) in the Gulf of Mexico. A suite of experiments is run using this modeling system, constructed by coupling a Navy Coastal Ocean Model simulation of the Gulf of Mexico to an atmospheric flux model. The modeling system is forced by wind fields produced from satellite scatterometer and atmospheric model wind data, and by numerical weather prediction air temperature data. The experiments are initialized from a data assimilative hindcast model run and then forced by surface fluxes with no assimilation for the time during which Hurricane Dennis impacted the region. Four experiments are run to aid in the analysis: one is forced by heat and momentum fluxes, one by only momentum fluxes, one by only heat fluxes, and one with no surface forcing. An equation describing the change in the upper ocean hurricane heat potential due to the storm is developed. Analysis of the model results show that surface heat fluxes are primarily responsible for widespread reduction (0.5°–1.5°C) of sea surface temperature over the inner West Florida Shelf 100–300 km away from the storm center. Momentum fluxes are responsible for stronger surface cooling (2°C) near the center of the storm. The upper ocean heat loss near the storm center of more than 200 MJ/m² is primarily due to the vertical flux of thermal energy between the surface layer and deep ocean. Heat loss to the atmosphere during the storm’s passage is approximately 100–150 MJ/m². The upper ocean cooling is enhanced where the preexisting mixed layer is shallow, e.g., within a cyclonic circulation feature, although the heat flux to the atmosphere in these locations is markedly reduced.  相似文献   

Evaporation over a Heterogeneous Land Surface: EVA_GRIPS and the LITFASS-2003 Experiment—An Overview     

Frank Beyrich  Heinz-Theo Mengelkamp 《Boundary-Layer Meteorology》2006,121(1):5-32

The Evaporation at Grid/Pixel Scale (EVA_GRIPS) project was realised in order to determine the area-averaged evaporation over a heterogeneous land surface at the scale of a grid box of a regional numerical weather prediction or climate model, and at the scale of a pixel of a satellite image. EVA_GRIPS combined surface-based and airborne measurements, satellite data analysis, and numerical modelling activities. A mesoscale field experiment, LITFASS-2003, was carried out in the heterogeneous landscape around the Meteorological Observatory Lindenberg (MOL) of the German Meteorological Service in May and June, 2003. The experiment was embedded in the comprehensive, operational measurement program of the MOL. Experimental determination of surface fluxes on a variety of spatial scales was achieved by employing micrometeorological flux stations, scintillometers, a combination of ground-based remote sensing instruments, and the Helipod, a turbulence probe carried by a helicopter. Surface energy fluxes were also derived from satellite data. Modelling work included the use of different Soil–Vegetation–Atmosphere Transfer schemes, a large-eddy simulation model and three mesoscale atmospheric models. The paper gives an overview on the background of EVA_GRIPS, and on the measurements and meteorological conditions during LITFASS-2003. A few general results are discussed.  相似文献   

Processing and quality control of flux data during LITFASS-2003   总被引：1，自引：0，他引：1  

Matthias Mauder  Claudia Liebethal  Mathias Göckede  Jens-Peter Leps  Frank Beyrich  Thomas Foken 《Boundary-Layer Meteorology》2006,121(1):67-88

Different aspects of the quality assurance and quality control (QA/QC) of micrometeorological measurements were combined to create a comprehensive algorithm which was then applied to experimental data from LITFASS-2003 (Lindenberg Inhomogeneous Terrain—Fluxes between Atmosphere and Surface: a long term Study). Eddy-covariance measurements of the latent heat flux were the main focus of the QA/QC efforts. The results of a turbulence sensor intercomparison experiment showed deviations between the different eddy-covariance systems on the order of 15%, or less than 30 W m⁻², for the latent heat flux and 5%, or less than 10 W m⁻², for the sensible heat flux. In order to avoid uncertainties due to the post-processing of turbulence data, a comprehensive software package was used for the analysis of experimental data from LITFASS-2003, including all necessary procedures for corrections and quality control. An overview of the quality test results shows that for most of the days more than 80% of the available latent heat flux data are of high quality so long as there are no instrumental problems. The representativeness of a flux value for the target land-use type was analysed using a stochastic footprint model. Different methods to calculate soil heat fluxes at the surface are discussed and a sensitivity analysis is conducted to select the most robust method for LITFASS-2003. The lack of energy balance closure, which was found for LITFASS-2003, can probably be attributed to the presence of low-frequency flux contributions that cannot be resolved with an averaging time of 30 min. Though the QA/QC system has been developed for the requirements of LITFASS-2003, it can also be applied to other experiments dealing with similar objectives.  相似文献   

Improved Representation of Land-surface Heterogeneity in a Non-hydrostatic Numerical Weather Prediction Model   总被引：2，自引：1，他引：2  

Felix Ament  Clemens Simmer 《Boundary-Layer Meteorology》2006,121(1):153-174

This study focuses on the relevance of accurate surface parameters, in particular soil moisture, and of parameterizations for heterogeneous land surfaces, for the prediction of sensible and latent heat fluxes by a mesoscale weather forecast model with horizontal grid resolution of 7 km. The analysis is based on model integrations for a 30-day period, which are compared both to flux measurements obtained from the LITFASS-2003 field experiment and to high-resolution-model (1-km grid spacing) results. At first, the relevance of improved parameter sets and input data compared to usual operational practice for an accurate prediction of near-surface fluxes is shown and discussed. It is demonstrated that an observation-based land-surface assimilation scheme leads to an improved soil moisture analysis, which is shown to be essential for the realistic simulation of surface fluxes. Secondly, the implementation of two efficient parameterization strategies for subgrid-scale variability of the surface, the mosaic and the tile approach, is presented. Using these methods, the simulations are in better agreement with measurements than simulations with simple aggregation methods that use effective surface parameters. Integrations with the mosaic approach reproduce high resolution simulations very well and more accurately than simulations with the tile method. Finally, the high resolution simulations are analyzed to justify and discuss the approximations underlying both methods.  相似文献