海岸边界层的非静力模式

建立了一个３级非静力边界层模式,并采用一种新的非局地反梯度闭合方案在杭州附近复杂地形区进行了数值模拟。通过与实测资料和静力条件下的模拟结果的比较,进一步分析了非局地闭合下非静力３级边界层模式的效能。结果表明,该模式比静力模式更能合理地模拟海岩边界层的风温场和湍流场,且模拟结果与实测更接近。     

山地露天矿自然通风风流与湍流结构的数值模拟

利用建立的三维非力能量闭合的大气边界层数值模式，研究了中性层结条件下某露天矿自然通风的风流和湍流结构特征及影响因子。研究表明：坑内水平风场在坑底或采壁处受地形的影响很大，在矿采深与开口宽度比较小或者来流风速随高度的切变不大时，坑内气流为平直型，有利于通风；反之坑内则形成环流，且在环流范围内较大的湍能，不利于通风，易产生高浓度的污染物。本模式模拟的结果还与风洞模拟和高阶闭合模式模拟的结果作了检验比较     

复杂下垫面地域边界层结构的三维细网格数值模拟

建立了一个可供复杂下垫面地域使用的非静力的三维细网格边界层模式，就复杂下垫面条件下的边界层结构和湍流特征作了以实例为对照的数值模拟试验，模式采用能量闭合方案，舍弃了静力近似。以实测资料为初台输入，同时还做了一些数值试验，分别获得了采用静力与非静力模式和不同闭合方案对ＰＢＬ模型的结果。     

山丘地形的陆面过程及边界层特征的模拟

将模式NP-89的陆面过程参数化方法应用到北京大学的三维复杂地形中尺度数值模式中, 得到了一个较理想的三维陆面过程及边界层模式, 利用这个改进的三维模式对20 km×20 km范围的山丘地形的陆面过程及边界层特征进行了数值模拟。模拟结果表明, 由于地形阻挡所造成山后的湍流较山前强, 进而造成近地面温度梯度和感热支出小, 最终造成山后的温度比山前的温度明显偏高; 而且随着山高的增加, 这种现象更加明显, 即该模式对山丘地形条件下的陆面过程和大气边界层特征具有较强的模拟能力; 模拟结果合理, 对研究过山气流形成机制、起伏地形大气边界层物理特征和污染物的扩散具有理论和应用价值。     

A One-Dimensional Finite-Element Boundary-Layer Model with a Vertical Adaptive Grid

A one-dimensional atmospheric boundary-layer model is developed using the finite element method and a 1.5-order e-l turbulence closure scheme. A vertical adaptive strategy is implemented, based upon an heuristic error estimator that depends upon properties of the layer, such as the stratification. The model is used to simulate a moderately stratified stable boundary layer as described in the GABLS (GEWEX Atmospheric Boundary-Layer Study, where GEWEX is the Global Water and Energy Cycle Experiment) First Intercomparison Project, and then a more complicated diurnal cycle, as used in the GABLS Second Intercomparison Project. In the stable boundary-layer experiment, it is shown that including the adaptive strategy can improve the performance of the model such that the error in the model is significantly less (greater than an order of magnitude with an effective resolution of 8 m) than that of the model without adaptivity. The model’s turbulence closure scheme and the adaptivity strategy also successfully simulate the different stability regimes present in the diurnal cycle simulation, and represented all of the expected features.     

复杂地形城市冬季边界层对气溶胶辐射效应的响应

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.     

边界层方案对华北低层O3垂直分布模拟的影响

利用WRF-Chem模式,采用3种边界层参数化方案 (YSU, MYJ和ACM2),针对1个晴空、静稳日 (2013年8月26日20:00—27日20:00(北京时)) 进行模拟,着重分析不同边界层参数化方案对夜间残留层形成及日出前后O₃浓度垂直分布形式的模拟效果,并与固城站地面及垂直同步观测资料进行对比。结果表明:3种边界层参数化方案均能够模拟出温度及风速的区域分布形式以及风温垂直结构的变化特征;相比之下,MYJ方案模拟的夜间边界层高度较YSU方案和ACM2方案明显偏高,该对比结果可能是导致近地面污染物浓度模拟差异的重要原因;在夜间稳定层结至日出后稳定状态打破的边界层结构演变过程中,采用YSU方案和ACM2方案模拟的温度和风速垂直扩线形式与观测结果更为接近;同样采用非局地闭合的YSU方案和同时考虑局地和非局地闭合的ACM2方案,对于边界层高度内O₃浓度垂直分布形式的模拟效果具有明显优势。     

精细PBL模式及其诊断应用

在已建立的一种三维非静力细网格Ｅ－ε湍能闭合的动力学框架基础上,作了一些改进的技术处理和试验,包括：（１）利用ＧＩＳ提供的地形资料,较精确地计算太阳辐射,进而诊断地面温度;（２）引进位势流概念,处理稳定层结条件下初始内插风场的风向变化;（３）引入动力学调整项Ｇ（αｏｂｓ－α）。在此基础上,就地理信息系统（ＧＩＳ）提供的一个 ６０ｋｍ×４８ｋｍ区域作了边界层结构和湍流特征的数值模拟试验,并与实测作了比较,讨论了精细ＰＢＬ模式的模拟效果,结果表明,新建的ＰＢＬ模式能较好地模拟表征出复杂下垫面地域的陡峭地形和不规则海岸线对局地风场和湍流场的动力和热力学作用。     

地形性中尺度环流的数值模拟及验证

建立了一个高分辨三维边界层诊断模式以模拟下垫面热力和动力的 非均匀性对边界层结构的影响。模式模拟了广东大亚湾核电站厂址区域（12 km×12 km） 47个典型天气系统下的地形性中尺度环流,其大坑的模拟风向、风速和温度与观测值 相比,风向差小于17.5#+[o]的概率为87.5%,风速比值在0.7～1.3之间的概率为72.9%, 温度差小于0.4#+[o]C的概率为72.9%。     

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

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。     

Different Turbulent Regimes and Vertical Turbulence Structures of the Urban Nocturnal Stable Boundary Layer

Turbulence in the nocturnal boundary layer(NBL) is still not well characterized, especially over complex underlying surfaces. Herein, gradient tower data and eddy covariance data collected by the Beijing 325-m tower were used to better understand the differentiating characteristics of turbulence regimes and vertical turbulence structure of urban the NBL. As for heights above the urban canopy layer(UCL), the relationship between turbulence velocity scale(V_TKE) and wind speed(V) was con...     

Modelling the One-Dimensional Stable Boundary Layer with an E−ℓ Turbulence Closure Scheme

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.     

深凹地形边界层风场与湍流场结构及扩散规律的数值研究

建立了一个模拟小尺度复杂地形边界层平均流场和湍流场结构分布特征的三维非静力细网格高阶矩湍流闭合模式,并将此模式与一个拉格朗日粒子随机游动大气扩散数值模式相联结,以边界层气象模式的输出作为扩散模式的输入,构成了一个大气扩和模拟系统,成功地模拟了某地实际深凹露天矿区和理想凹坑地形两种情况下的平均流场、雷诺应力和湍流通量场,分析了其分布特征,并模拟了矿坑内污染物的散布规律     

A STUDY OF 1.5-ORDER CLOSURE TURBULENCE MODEL

Based on turbulence theory,a 1.5-order closure turbulence model is established.The model incorporating with theground surface energy budget equation is constructed by means of a vertical one-dimensional(1-D)40-levelgrid-mesh.The numerical results reveal the 24-h evolution of the clear planetary boundary layer comparing with theWangara boundary layer data of days 33—34.The model also takes into account some physical processes of radiativetransfer and baroclinicity,revealing some important characteristics observed in the boundary layer,especially for theevolution of the mixed layer and low-level jet.The calculated results are in good agreement with the observational data.On the other hand,we also run the high-resolution model of the planetary boundary layer in the Mesoscale Model Ver-sion 4(MM4)with the same physical processes and initial conditions.The results show that the high-resolution modelcan not reveal those important characteristics as the 1.5-order closure model did.In general,it is shown that the 1.5-or-der closure turbulence model based on turbulence theory is better in rationality and reality.     

复杂地形风场的精细数值模拟

风能是一种重要气候资源,随着我国风电规模的迅速增大,发展风能资源评估系统和风功率预测系统已成为一项重要的研究内容。国内外对复杂地形风场结构的数值模拟有大量研究,随着计算机能力增强,以往用于空气动力学精细流场计算的计算流体力学(Computational Fluid Dynamics,CFD)模式越来越多地在气象领域得到应用,人们开始研究用中尺度预报模式和CFD模式结合进行复杂地形风场的数值模拟。本文的耦合模式系统采用中尺度气象模式(WRF),通过嵌套网格到内层尺度(一般是几公里),然后通过耦合CFD模式Fluent软件获得高分辨率(水平30~100 m,垂直150 m高度以下10 m)的风速分布资料,得到精细化的风场信息。通过对鄱阳湖北部区域和云南杨梅山复杂地形的风场模拟,提供了风能评估和预报的一种可行的方法。     

Building morphological characteristics and their effect on the wind in Beijing

An urban boundary layer model (UBLM) is improved by incorporating the effect of buildings with a sectional drag coefficient and a height-distributed canopy drag length scale. The improved UBLM is applied to simulate the wind fields over three typical urban blocks over the Beijing area with different height-to-width ratios. For comparisons, the wind fields over the same blocks are simulated by an urban sub-domain scale model resolving the buildings explicitly. The wind fields simulated from the two different methods are in good agreement. Then, two-dimensional building morphological characteristics and urban canopy parameters for Beijing are derived from detailed building height data. Finally, experiements are conducted to investigate the effect of buildings on the wind field in Beijing using the improved UBLM.     

大气边界层物理与大气环境过程研究进展

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。     

Using a Modified Soil-Plant-Atmosphere Scheme （MSPAS） to Simulate the Interaction between Land Surface Processes and Atmospheric Boundary Layer in Semi-Arid Regions

This paper uses a Modified Soil-Plant-Atmosphere Scheme (MSPAS) to study the interaction betweenland surface and atmospheric boundary layer processes. The scheme is composed of two main parts:atmospheric boundary layer processes and land surface processes. Compared with SiB and BATS, which arefamous for their detailed parameterizations of physical variables, this simplified model is more convenientand saves much more computation time. Though simple, the feasibility of the model is well proved inthis paper. The numerical simulation results from MSPAS show good agreement with reality. The schemeis used to obtain reasonable simulations for diurnal variations of heat balance, potential temperature ofboundary layer, and wind field, and spatial distributions of temperature, specific humidity, vertical velocity,turbulence kinetic energy, and turbulence exchange coefficient over desert and oasis. In addition, MSPAS isused to simulate the interaction between desert and oasis at night, and again it obtains reasonable results.This indicates that MSPAS can be used to study the interaction between land surface processes and theatmospheric boundary layer over various underlying surfaces and can be extended for regional climate andnumerical weather prediction study.     

The Adaptation of the Atmospheric Boundary Layer to a Change in Surface Roughness

The adaptation of the atmospheric boundary layer to a change in the underlying surface roughness is an interesting problem and hence much research, theoretical, experimental, and numerical, has been undertaken. Within the atmospheric boundary layer an accurate numerical model for the turbulent properties of the atmospheric boundary layer needs to be implemented if physically realistic results are to be obtained. Here, the adaptation of the atmospheric boundary layer to a change in surface roughness is investigated using a first-order turbulence closure model, a one-and-a-half-order turbulence closure model and a second-order turbulence closure model. Perturbations to the geostrophic wind and the pressure gradients are included and it is shown that the second-order turbulence closure model, namely the standard k - model, is inferior to a lower-order closure model if a modification to limit the turbulent eddy size within the atmospheric boundary layer is not included within the model.