An Analytical Footprint Model For Non-Neutral Stratification   总被引：9，自引：6，他引：9  

Robert Kormann  Franz X. Meixner 《Boundary-Layer Meteorology》2001,99(2):207-224

We propose an analytical model for the so-called footprint of scalar fluxes in the atmospheric boundary layer. It is the generalization of formulations already given in the literature, which allows to account for thermal stability. Our model is only marginally more complicated than these, and it is therefore simple enough to be applicable for a routine footprint analysis within long-term measurements. The mathematical framework of our model is a stationary gradient diffusion formulation with height-independent crosswind dispersion. It uses the solution of the resulting two-dimensional advection – diffusion equation for power law profiles of the mean wind velocity and the eddy diffusivity. To find the adjoint Monin–Obukhov similarity profile, we propose two different approaches, a purely analytical one and a simplenumerical error minimalization.  相似文献   

地形和层结变化对内潮生成影响的数值模拟研究     

刘昆  徐振华  尹宝树 《海洋科学》2016,40(11):148-154

基于ROMS(Regional Ocean Modeling System)模式,设计了9组理想数值实验,研究了内潮的产生对地形和背景层结环境的敏感性。结果表明:高斯海脊两侧地形梯度较大的超临界坡面处是内潮的主要源区;地形和层结环境的变化对内潮生成有很大影响;如地形和层结保持不变,不同的网格水平分辨率和垂向层数条件下估算的内潮转换率存在差别;地形和跃层的相对空间关系对内潮生成及其引起的水体混合强度存在影响。高分辨率的地形和合适的背景层结是内潮模拟的关键。该结论对于内潮形成的数值模拟研究有一定参考价值。  相似文献   

千岛湖水温垂直分层的空间分布及其影响因素   总被引：1，自引：0，他引：1  

白杨  张运林  周永强  施坤  刘明亮  杨桂军 《海洋与湖沼》2016,47(5):906-914

湖泊热力分层及热力循环深刻影响深水湖泊生态系统。随着全球气候变暖,湖泊热力过程会发生显著变化。作为深水水库型湖泊,千岛湖的热力过程与水环境的变化紧密相连,为了分析千岛湖水体水温、湖泊热力分层参数(温跃层深度、厚度和强度)的分布,探讨温跃层深度与水温、水体透明度以及水深之间的关系,本文根据2014年7月份与2015年5月份对千岛湖全湖60个采样点的水体理化指标的垂向分布调查数据,计算得到千岛湖热力分层参数,进而分析其时空分布特征及主要影响因素。结果表明,千岛湖水体水温垂直分布呈现正温分布,春夏季全湖范围内均存在不同程度的温度分层现象,温跃层深度、厚度和强度均从上游河口向下游敞水区逐步增大,这种空间变化的趋势在7月份比5月份更显著。水温、透明度和水深是影响温跃层深度的主要因素。夏季湖泊热力分层稳定期温跃层深度与表层水温(0—2m)存在显著负相关关系,与透明度和水深存在正相关关系。  相似文献   

露天煤矿边坡稳定性实例分析及优化设计          下载免费PDF全文

宋国龙 《探矿工程》2016,43(10):30-35

结合内蒙古某露天煤矿的边坡实例,综合运用现有的工程地质资料、理论分析以及计算等手段,对该露天矿边坡工程地质条件、稳定性进行了分析和评价,提出了优化设计方案和滑坡治理建议。最后,从技术和工程方面提出了露天矿边坡稳定性的防治措施。  相似文献   

Parameterization of Sheared Entrainment in a Well-developed CBL.Part Ⅱ:A Simple Model for Predicting the Growth Rate of the CBL   总被引：1，自引：0，他引：1  

Peng Liu  Jianning Sun  Lidu Shen 《大气科学进展》2016,33(10):1185-1198

Following the parameterization of sheared entrainment obtained in the companion paper, Liu et al. (2016), the present study aims to further investigate the characteristics of entrainment, and develop a simple model for predicting the growth rate of a well-developed and sheared CBL. The relative stratification, defined as the ratio of the stratification in the free atmosphere to that in the entrainment zone, is found to be a function of entrainment flux ratio (A _e). This leads to a simple expression of the entrainment rate, in which A _e needs to be parameterized. According to the results in Liu et al. (2016), A _e can be simply expressed as the ratio of the convective velocity scale in the sheared CBL to that in the shear-free CBL. The parameterization of the convective velocity scale in the sheared CBL is obtained by analytically solving the bulk model with several assumptions and approximations. Results indicate that the entrainment process is influenced by the dynamic effect, the interaction between mean shear and environmental stratification, and one other term that includes the Coriolis effect. These three parameterizations constitute a simple model for predicting the growth rate of a well-developed and sheared CBL. This model is validated by outputs of LESs, and the results show that it performs satisfactorily. Compared with bulk models, this model does not need to solve a set of equations for the CBL. It is more convenient to apply in numerical models.  相似文献   

河北中南部连续12 d重霾污染天气过程特征及影响因素分析   总被引：5，自引：4，他引：1  

郭蕊  段浩  马翠平  赵娜  曲晓黎  郭卫红  张金满 《气象》2016,42(5):589-597

2013年12月14—25日,河北中南部地区发生了一次长达12 d的重霾污染天气过程。本文通过对同期气象条件、流场、污染物特征进行分析,探讨了这次过程的成因。此次污染过程与霾密切相关,具有持续时间长、范围广及强度大的特点;在静稳的大尺度气象条件和近地面大气层结下,污染物沿近地面风场的弱辐合区迅速积累,是重覆污染天气形成的关键;此次重霾污染天气过程中有两次弱冷空气活动,两次冷空气影响层次有所不同但影响时间均较短,不能彻底改变静稳大气层结,对污染物的扩散能力有限,重霾污染天气得以长时间持续。  相似文献   

近10a新疆短时强降水湿度层结及大气能量结构特征分析     

毛列尼.阿依提看  玉素甫.木沙  郭品文 《沙漠与绿洲气象(新疆气象)》2017,11(2):43-49

为更好地把握中亚低涡造成新疆短时强降水天气过程的机理特征,利用温度露点温度廓线图(T-lnP图)和大气位温-风矢能量图(V-3θ图)研究了中亚低涡背景下新疆短时强降水的湿度特征和大气能量结构特征。主要结论有:(1)根据对短时强降水T-lnP图及湿度特征的分析统计,将短时强降水分成三类:对流层高低层干而中层湿度大型、对流层中层干燥型、对流层整层湿度都显著型。其中第一类最多,占短时强降水总个例的60%;而第二类和第三类分别占27.5%、12.5%。(2)一般在短时强降水天气发生前V-3θ图特征为:三条θ曲线呈曲折增长;有"顺滚流"结构存在;有"蜂腰"形构造;有较为浅薄的超低温层存在。  相似文献   

The hydrodynamic response of the York River estuary to Tropical Cyclone Isabel, 2003   总被引：3，自引：0，他引：3  

Wenping Gong  Jian Shen  William G. Reay 《Estuarine, Coastal and Shelf Science》2007,73(3-4):695-710

Hurricane Isabel made landfall along the North Carolina coast on September 18, 2003 (UTC 17:00) and the storm surge exceeded 2.0 m in many areas of the Chesapeake Bay and in the York River estuary. River flooding occurred subsequently, and the peak river discharge reached 317 and 104 m³ s⁻¹ in the Pamunkey and Mattaponi rivers, respectively. The York River estuary experienced both storm surge and river flooding during the event and the estuary dynamics changed dramatically. This study investigates the hydrodynamics of the York River estuary in response to the storm surge and high river inflows. A three-dimensional model was used to investigate the changes of estuarine stratification, longitudinal circulation, salt flux mechanisms, and the recovery time required for the estuary to return to its naturally evolved condition without the storm. Results show that the salt flux was mainly caused by advection, which was induced by the barotropic gradient during the storm event. The net salt flux increased by a factor of 30 during the rise of the storm surge. However, the large amount of salt transported into the estuary was quickly transported out of the estuary as the barotropic gradient reversed during the descent of the storm surge. Subsequent high freshwater inflow influenced the estuarine circulation substantially. The estuary changed from a partially mixed estuary to a very stratified estuary for a prolonged period. The model results show that it will take about 4 months for the estuary to recover to its naturally evolved salinity distribution after the impacts of the storm surge and freshwater pulse.  相似文献   

Simulation of the seasonal thermal structure in the Bohai Sea   总被引：1，自引：0，他引：1  

Huang Daji  Su Jilan  Chen Zongyong 《海洋学报(英文版)》1995,14(4):461-474

The seasonal thermal structure in the Bohai Sea are examined with a three-dimensional boroclinic primitive equation model for shelf sea.The evolution of the seasonal thermal stratification is well simulated.The stratification appears early in April,first in the area off Qinhuangdao and it is well developed in the middle of May.It intensifies with synoptic and neap-spring fluctuations throughout the summer and reaches its maximum in the middle of July.Eventually,it is destroyed at the end of September.There are cold water belts between well-mixed and stratified regions.They are loGated on the mixed side of tidal fronts,and coincide with the isolines for a temperature difference of 1-2℃ between surface and bottom.The sea surface temperature (SST) distribution shows local maxima at the head of three bays and to the south of Qinhuangdao during the summer.The Bohai Sea responds to the variability in the atmospheric forcing and in tides with the synoptic and neap-spring variations of SST,as well as in the stratification and in variable positions of tidal fronts.  相似文献   

On Conditions of Phytoplankton Blooms in the Coastal Waters of the North-Western East/Japan Sea   总被引：1，自引：0，他引：1  

Yury Zuenko  Marina Selina  Inna Stonik 《Ocean Science Journal》2006,41(1):31-41

Seasonal changes of abundance of the main phytoplankton groups of species (diatoms, dinoflagellates, chrysophytes, small flagellates and cryptophytes) and a set of environmental parameters were investigated in coastal and preestuarine waters of Peter the Great Bay (East/Japan Sea) in May-October of 1998 and 1999. Three periods of mass development were revealed: spring, summer and autumn blooms, with successive change of species. The conditions favourable for each group of species were determined. Driving mechanisms of the succession include nutrients transport through seasonal pycnocline by turbulent mixing, terrestrial nutrients supply by monsoon floods, nutrients supply by upwellings, and light control by the thickness of upper mixed layer. Summer succession could be explained by a simple SST-MLD diagram similar to Pingree S-kh diagram with sea surface temperature as indicator of stratification (S) and mixed layer depth as indicator of light availability (kh).  相似文献