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1.
森林下垫面陆面物理过程及局地气候效应的数值模拟试验 总被引：5，自引：0，他引：5
文中基于大气边界层和植被冠层微气象学基本原理 ,建立了一个森林植被效应的陆面物理过程和二维大气边界层数值模式。并应用该模式进行了植被和土壤含水量等生物和生理过程在陆面过程和局地气候效应方面的数值模拟试验。所得数值模拟试验结果与实际情况相吻合。结果表明 ,应用该模式可获得植被温度、植被冠层内空气温度、地表温度日变化特征 ;森林下垫面大气边界层风速、位温、比湿、湍流交换系数的时空分布和日变化特征。该模式还可应用于不同下垫面 ,模拟陆面物理过程与大气边界层相互作用机制及其局地气候效应的研究 ,这将为气候模式与生物圈的耦合研究奠定一个良好的基础。 相似文献
2.
使用WRF中尺度数值模式, 分别选用两种不同的边界层参数化方案 (MYJ, YSU) 和3种陆面参数化方案 (SLAB, Noah, RUC), 对2004年7月1日08:00—7月4日20:00 (北京时) 北京地区夏季边界层结构进行1 km的高分辨模拟。对比分析了近地面层风场、温度场以及边界层的日变化特征, 结果发现:WRF模式基本模拟出了北京夏季边界层的日变化特征; 在边界层方案中, MYJ方案描述的边界层结构较YSU方案合理; Noah陆面模式较好地反映了城市的热岛效应; 无降水时, 风速及边界层高度对于陆面过程不敏感, 而降水发生后, 陆面过程对于边界层结构的影响增大; 各方案模拟的城区风速明显偏大, 这是因为没有充分考虑城市建筑物的阻力作用。 相似文献
3.
边界层和陆面过程对中国暴雨影响研究的进展 总被引：1，自引：0，他引：1
总结了近年来我国学者关于边界层和陆面过程对中国暴雨影响的研究成果。此类研究主要应用中尺度数值模式,有的对边界层过程和陆面过程做敏感性试验,有的则对模式中边界层和陆面过程参数化作改进。结果表明：边界层和陆面过程对我国暴雨有明显影响。主要表现在影响暴雨的强度以及使暴雨中心位置有一定的变动,但决定暴雨发生发展的主要因子是大中尺度动力过程。对边界层和陆面过程的改进能有效改善数值模式对暴雨的模拟。 相似文献
4.
不同边界层参数化方案和陆面过程参数化方案对一次梅雨锋暴雨显式对流模拟的影响分析 总被引：1，自引：0，他引：1
利用WRF模式对2007年7月8日淮河地区特大暴雨过程开展显式对流(1.1 km)模拟试验,比较两种边界层参数化方案和三种陆面过程参数化方案对降水模拟的影响。结果表明,不同边界层参数化方案和陆面过程参数化方案主要影响模拟的强降水位置和强度,而对雨带位置的影响不大。采用MYJ边界层方案模拟的强降水更接近观测,采用YSU方案模拟的强降水偏弱;陆面过程参数化方案对比,简单的热扩散方案模拟的强降水最强、最接近观测,而RUC方案模拟的强降水最弱,Noah方案居中;同时改变陆面方案和边界层方案比单一改变其中一种方案对模拟降水的影响更大。造成强降水模拟差异的主要原因是模拟的近地面(约1 km以下)大气的湿度和温度不同,导致支持对流发生发展的入流空气的对流有效位能(CAPE)不同,进而影响模拟的对流强度和地面降水量。对强降水模拟较好的试验模拟的近地面大气湿度更大,环境入流空气的CAPE更大,对流发展更强,地面降水也更强。 相似文献
5.
地表作为大气模块的下垫面,为大气模块提供边界条件,地形对于模式结果的准确性起到至关重要的作用。现有的陆面过程模式在陆面同一网格内的次网格单元采用相同的大气强迫量,没有考虑次网格地形对网格内大气强迫量的影响,这关系到模式对气象要素和陆气交换量的模拟水平。本文在陆面模式NOAH处理次网格单元的同时,将输入的大气强迫量根据其与地形高度的关系进行修订,提出新的次网格地形的参数化方案,并引入到WRF（Weather Research and Forecasting）模式中进行数值试验,通过3组数值模拟试验,与未改进的方案和细网格方案分析比较,探讨新参数化方案对WRF 模式模拟结果的影响。结果表明:地形越复杂区域,次网格地形的影响越大。本文引入的新陆面次网格地形方案对天山山脉和昆仑山脉以及青藏高原南部的地表气温的模拟有较大改善,模拟的地表气温在大范围区域内都更贴近细网格方案。虽然新陆面次网格地形方案和细网格试验都对温度的模拟结果都有改善,但新陆面次网格地形方案对降水的模拟改善甚微,而细网格试验对降水模拟却有改进,这是由于细网格试验在陆面和大气网格都进行了细化,而新陆面次网格地形方案只考虑了陆面次网格的影响。具体来说,新陆面次网格地形方案对温度的模拟结果改进是通过改变地表向上长波和地表感热实现的。而细网格试验由于同时细化了大气和陆面的空间网格,对降水和温模拟的改进是通过综合改变地表能量平衡实现的。 相似文献
6.
水、陆不均匀条件下大气边界层结构的模拟研究 总被引：2，自引：0，他引：2
应用2004年白洋淀野外观测实验资料,对白洋淀地区水、陆不均匀分布条件下的大气边界层开展了数值模拟试验,结果表明:由于下垫面的热力差异,在360多km2的白洋淀地区,地表特征分布的不均匀可以引发弱的局地环流,影响大气边界层内温度和湿度的空间分布;在500m高度以下,下垫面不均匀分布对湍流动能有明显影响.最后将模拟结果与观测资料进行了对比检验. 相似文献
7.
绿洲效应的模拟及内外因子的敏感性实验 总被引：7，自引：2，他引：5
利用一个已发展的陆面物理过程参数化方案与大气边界层数值模式耦合,模拟了半干旱区绿洲戈壁非均匀下垫面的陆面物理过程及其与大气边界层的相互作用,成功地描绘了绿洲戈壁局地气候效应,并进行了绿洲戈壁局地气候效应对于降水、绿洲水平尺度和植被结构等若干内外因子的敏感性实验.结果表明:绿洲的最小临界尺度为5～10 km之间,最大临界尺度为55～65 km之间,而最利于绿洲维持的尺度范围为20 km左右,这一结论与我国西部地区现存的绿洲尺度统计结果十分一致;绿洲植被覆盖率为0.6左右时,最利于绿洲发展.另外对植被空间分布方式和绿洲植被组成比例上也进行了数值实验,并对影响绿洲生存和持续发展的内、外因子气候效应的影响力量级进行了分级.这些结果对于深入了解绿洲气候的形成和维持机理具有重要的意义. 相似文献
8.
本文建立一个三维非静力边界层模式对杭州湾附近复杂地形域区进行了数值模拟。要用常用的能量闭合和一 新的非局地反梯度闭合方案结合实测资料,以验证不同闭合方案模拟实际大气的能力,进一步分析三维边界层模式的效能结果表明,两种闭合方案都能较好的模拟澳陆环流及温度场,而反梯度闭合比能量闭合更能细致、敏感的模拟湍流场随地形的变化,且模拟结果与实测接近。 相似文献
9.
大气边界层物理与大气环境过程研究进展 总被引：3，自引：2，他引：1
总结了近5年来中国科学院大气物理研究所大气边界层物理和大气化学国家重点实验室(LAPC)在第二代超声风速温度仪研制、城市边界层研究、复杂地形大气边界层探测与数值模拟、湍流机理研究、大气污染模式发展与应用等领域的主要进展,其中,第二代超声风速温度仪的野外对比测试结果表明其主要性能完全达到了国际先进水平;北京城市化发展使得北京325 m气象塔周边近地面流场已经具备了典型城市粗糙下垫面的流场特征,近地面夏季平均风速呈现非常明显的逐年递减趋势;北京沙尘暴大风时期湍流运动主要是小尺度湍涡运动,而大风的概率分布偏离高斯分布,风速较大的一侧概率分布呈指数迅速衰减,大风中风速很大的部分具有分形特征;珠穆朗玛峰北坡地区两次综合强化探测实验是迄今为止在青藏高原大型山地中实施的针对山地环流和物质／能量交换最为全面和连续的大气过程探测实验;白洋淀地区的观测研究表明,非均匀边界层具有一般边界层不具备的特点,无论是边界层结构还是湍流输送方面,水、陆边界层之间存在一定的差异,凸显其地表非均匀性的作用;为了解决不同尺度、不同类型的大气污染问题和实际应用,研制或发展完善了多套大气污染模式系统,包括全球大气化学模式、区域大气污染数值模式、城市大气污染数值模式和微小尺度(如街区尺度)范围内污染物输送扩散模式。 相似文献
10.
北京海淀地区大气边界层的数值模拟研究 总被引：10，自引：1，他引：10
采用北京大学的三维复杂地形中尺度数值模式,利用Landsat-TM卫星影像图得到的地表状况计算陆气之间的能量平衡过程,模拟了北京海淀地区大气边界层的风、温场结构以及污染物浓度分布,进而模拟了由于汽车尾气的排放而转化成的气溶胶的浓度分布.模拟表明城郊之间存在热岛效应,边界层风场受到热岛的热力作用以及地形的动力作用影响.污染物及气溶胶浓度也存在城乡差别,最大浓度出现在城区的下风方向. 相似文献
11.
We study the vorticity field induced by flow around surface mounted obstacles, focussing on the streamwise vorticity. A combination of analytical and numerical model results indicates that the mechanisms for the generation of the mean flow vorticity, as well as its form and magnitude, are not significantly influenced by turbulence, at least for a first-order turbulence closure. This result is in qualitative agreement with suggestions of previous studies. The numerical model is used to simulate flow around an asymmetric hill and, in terms of the shape and positioning of the trailing vortex, good agreement is found between the simulations and observations. However, the strength of the vortex appears to be significantly underestimated by the numerical model. The influence of the slope of the hill and of the angle of incidence of the mean wind on the trailing vorticity is also investigated. Finally, it is found that the occurrence of a dominant trailing vortex, at least one of the strength predicted by the numerical model, does not have a significant impact on the momentum budget of the downstream boundary layer. 相似文献
12.
Flow over the summit of an isolated hill 总被引：5，自引：0，他引：5
P. J. Mason 《Boundary-Layer Meteorology》1986,37(4):385-405
Observations of the mean flow and turbulence statistics over the summit of an isolated, roughly circular hill, Nyland hill, are presented, Nyland hill rises 70 m above the surrounding terrain and has a base diameter of about 500 m. The summit of the hill is very smooth and allows representative measurements to be made close to the surface. The flow speed 8 m above the summit is increased by a factor of 2 over the upstream speed 8 m above level terrain, and flow separation occurs in the lee of the hill. The mean velocity profile over the summit shows an increase in velocity with height up to about 2 m and then a near constant velocity between 2 and 16 m. The flow perturbation relative to the upstream profile is thus a maximum at about 2 m. The measurements of turbulence structure show how the influence of the hill depends on the length scale of the turbulent eddies involved. Scales greater than the scale of the hill are modified through the flow speed-up whilst scales shorter than the hill suffer complex changes. The short-scale turbulence over the summit is only in local equilibrium in the lowest fraction of a metre. Above this equilibrium region, there is a complex adjustment towards the rapid distortion dynamics which appear to dominate at heights above about 8 m. The detailed results are compared with previous studies and available theories. 相似文献
13.
本文采用二阶矩湍流闭合方案，分别就非静力和准静力两种条件建立ＰＢＬ数值模式，并模拟了二维山脊流场的结构，计算了二维山体对气流平均场和湍流场的影响。计算结果表明，无论是平均场还是湍流场，采用准静力假设都会造成模拟结果的较大偏差，且对平均场的影响比对湍流场的影响更为显著。两种模式计算结果的差别还随地形坡度和背景风增大而增大。 相似文献
14.
三维非静力E—ε闭合模式对山体流场及浓度分布的模拟 总被引：4，自引：0，他引：4
本文采用三维非静力E-ε闭合模式,在对流层边界层方程组中,加入湍能和耗散率方程描述边界层中的湍流运动。求解孤立三维山地地形上的流场、湍流场和浓度场,并分析地形对气流的影响及对污染物浓度分布的影响。同时做了不同坡度和不同风速下的孤立三维山体的流场、湍流场和浓度场比较。数值计算结果表明,地形能改变气流运动,气流过山时将出现分支现象,山后背坡有反向回流出现,并且回流区大小随着山体坡度的增大而增大。山体对气流的阻挡作用随山体高度的增加而更明显,随风速的增加而减弱。湍能及耗散率随高度衰减较快。随着山体坡度增加,山前气流的垂直速度也增加,湍流运动更强。风速大时湍流运动越显著。污染物在山前出现辐散,迎风坡是浓度高值区,山后背风坡也是相对高值区。山坡度越大,山前迎风坡污物浓度越高。 相似文献
15.
晴天地表太阳辐射的参数化 总被引：2，自引：0，他引：2
讨论了晴天地表太阳总辐射和地表太阳净辐射瞬时值的参数化方法。首先利用辐射传输模式和中纬度夏季标准大气廓线,分谱带计算晴天各种大气条件下地表反射率取定值时的地表太阳总辐射,并把所得的结果作为标准资料,提出参数化方案。然后将地表反射率的影响作为误差项进行订正,从而得到各种地表反射率条件下的晴天地表太阳净辐射的计算方法。该方法的拟合精度较高,拟合值与辐射模式标准值的平均相对误差在0.3%以下。该参数化公式可以用于大尺度数值模式中地表辐射平衡的计算,以期达到地表辐射平衡计算与模式积分同步进行的目的。 相似文献
16.
Anirban Garai Eric Pardyjak Gert-Jan Steeneveld Jan Kleissl 《Boundary-Layer Meteorology》2013,148(1):51-72
Previous laboratory and atmospheric experiments have shown that turbulence influences the surface temperature in a convective boundary layer. The main objective of this study is to examine land-atmosphere coupled heat transport mechanism for different stability conditions. High frequency infrared imagery and sonic anemometer measurements were obtained during the boundary layer late afternoon and sunset turbulence (BLLAST) experimental campaign. Temporal turbulence data in the surface-layer are then analyzed jointly with spatial surface-temperature imagery. The surface-temperature structures (identified using surface-temperature fluctuations) are strongly linked to atmospheric turbulence as manifested in several findings. The surface-temperature coherent structures move at an advection speed similar to the upper surface-layer or mixed-layer wind speed, with a decreasing trend with increase in stability. Also, with increasing instability the streamwise surface-temperature structure size decreases and the structures become more circular. The sequencing of surface- and air-temperature patterns is further examined through conditional averaging. Surface heating causes the initiation of warm ejection events followed by cold sweep events that result in surface cooling. The ejection events occur about 25 % of the time, but account for 60–70 % of the total sensible heat flux and cause fluctuations of up to 30 % in the ground heat flux. Cross-correlation analysis between air and surface temperature confirms the validity of a scalar footprint model. 相似文献
17.
Numerical Simulation Experiment of Land Surface Physical Processes and Local Climate Effect in Forest Underlying Surface 总被引：1，自引：0，他引：1 
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下载免费PDF全文 LIU Shuhu PAN Ying DENG Yi MA Mingmin JIANG Haimei LIN Hongtao JIANG Haoyu LIANG Fuming LIU Heping WANG Jianhua 《Acta Meteorologica Sinica》2006,20(1):72-85
Based on the basic principles of atmospheric boundary layer and plant canopy micrometeorology, a forest underlying surface land surface physical process model and a two-dimensional atmospheric boundary layer numerical model are developed and numerical simulation experiments of biosphere and physiological processes of vegetation and soil volumetric water content have been done on land surface processes with local climate effect. The numerical simulation results are in good agreement with realistic observations, which can be used to obtain reasonable simulations for diurnal variations of canopy temperature, air temperature in canopy, ground surface temperature, and temporal and spatial distributions of potential temperature and vertical wind velocity as well as relative humidity and turbulence exchange coefficient over non-homogeneous underlying surfaces. It indicates that the model developed can be used to study the interaction between land surface process and atmospheric boundary layer over various underlying surfaces and can be extended to local climate studies. This work will settle a solid foundation for coupling climate models with the biosphere. 相似文献
18.
HUBEX试验区近地面层的湍流输送 总被引：8，自引：1，他引：7
1998年淮河流域能量和水循环试验(HUBEX)期间曾进行了1个月的近地面层湍流观测.分析不稳定条件下湍流的统计特性和谱特征,并与Monin-Obukhov相似理论进行了比较.结果表明,不稳定的时候各湍流量的统计特征与相似理论的预期相符.虽然不稳定条件下温度和湿度涨落的相关系数很高,谱的式样也相近,但湿度谱的峰值频率高于温度谱.协谱曲线的形状显示感热通量的谱峰较宽,表现出w和T在较宽范围的强相关性,而水汽通量谱在高频段下降很快,说明水汽的输送更多地出现在低频部分.从谱相关系数可见,在近中性的时候,各尺度湍流涡的热量输送效率普遍较低,随着不稳定性增强而显著提高.分析还发现,不论不稳定性的程度如何,小尺度湍流的水汽输送效率都较低.水汽通量谱的相关系数随稳定度的变化不如热通量的谱相关系数大,表明近中性时除小尺度湍流外其他湍流涡的水汽输送效率高于热量输送. 相似文献
19.
Progress on practical problems such as quantifying gene flow and seed dispersal by wind or turbulent fluxes over nonflat terrain
now demands fundamental understanding of how topography modulates the basic properties of turbulence. In particular, the modulation
by hilly terrain of the ejection-sweep cycle, which is the main coherent motion responsible for much of the turbulent transport,
remains a problem that has received surprisingly little theoretical and experimental attention. Here, we investigate how boundary
conditions, including canopy and gentle topography, alter the properties of the ejection-sweep cycle and whether it is possible
to quantify their combined impact using simplified models. Towards this goal, we conducted two new flume experiments that
explore the higher-order turbulence statistics above a train of gentle hills. The first set of experiments was conducted over
a bare surface while the second set of experiments was conducted over a modelled vegetated surface composed of densely arrayed
rods. Using these data, the connections between the ejection-sweep cycle and the higher-order turbulence statistics across
various positions above the hill surface were investigated. We showed that ejections dominate momentum transfer for both surface
covers at the top of the inner layer. However, within the canopy and near the canopy top, sweeps dominate momentum transfer
irrespective of the longitudinal position; ejections remain the dominant momentum transfer mode in the whole inner region
over the bare surface. These findings were well reproduced using an incomplete cumulant expansion and the measured profiles
of the second moments of the flow. This result was possible because the variability in the flux-transport terms, needed in
the incomplete cumulant expansion, was shown to be well modelled using “local” gradient-diffusion principles. This result
suggests that, in the inner layer, the higher-order turbulence statistics appear to be much more impacted by their relaxation
history towards equilibrium rather than the advection-distortion history from the mean flow. Hence, we showed that it is possible
to explore how various boundary conditions, including canopy and topography, alter the properties of the ejection-sweep cycle
by quantifying their impact on the gradients of the second moments only. Implications for modelling turbulence using Reynolds-averaged
Navier Stokes equations and plausible definitions for the canopy sublayer depth are briefly discussed. 相似文献
20.
A model of the planetary boundary layer over a snow surface has been developed. It contains the vertical heat exchange processes due to radiation, conduction, and atmospheric turbulence. Parametrization of the boundary layer is based on similarity functions developed by Hoffert and Sud (1976), which involve a dimensionless variable, ζ, dependent on boundary-layer height and a localized Monin-Obukhov length. The model also contains the atmospheric surface layer and the snowpack itself, where snowmelt and snow evaporation are calculated. The results indicate a strong dependence of surface temperatures, especially at night, on the bursts of turbulence which result from the frictional damping of surface-layer winds during periods of high stability, as described by Businger (1973). The model also shows the cooling and drying effect of the snow on the atmosphere, which may be the mechanism for air mass transformation in sub-Arctic regions. 相似文献