Sensitivity analysis of planetary boundary layer schemes using the WRF model in Northern Colombia during 2016 dry season     

《Dynamics of Atmospheres and Oceans》2021

This study conducted meteorological simulations in northern Colombia by analyzing different planetary boundary layer (PBL) schemes available in the numerical Weather Research and Forecasting (WRF) model. The study area included three nested domains with horizontal resolutions of 18 km, 6 km, and 2 km, with 38 vertical levels. The evolution and structure of the PBL were analyzed during the driest months (March, April, and May 2016) and in regions with the highest particulate matter concentrations. Sensitivity analysis of the WRF model was performed with two local and two non-local PBL schemes. The results were validated using observations of the surface air temperature, relative humidity, and surface wind speed collected from three meteorological stations in the area. The PBL heights were experimentally determined using radiosonde data provided by a station located in the center of the study area. Variations in PBL heights were estimated using linear regression methods and minimization of statistical errors for the bulk Richardson number, as well as analysis of vertical temperature and wind profiles. The WRF model reliably reproduced the daily values and diurnal cycles of temperature, relative humidity, and wind speed within the PBL and accounted for the influence of topography and sea breezes. Horizontal heat advection dominates the upwelling of air masses when sea breezes are active. The onshore wind direction starts to change from east to northwest, implying a decay in the land breeze regime. All schemes overestimate the mixing height and tend to underestimate surface air temperature values at night. All show wetter conditions and underestimate wind speed. Although the non-local Yonsei University (YSU) scheme shows the best performance, it also shows the largest sources of errors when determining the behavior of the surface layer during stable conditions. Relative humidity and wind speed estimates provided by the local Mellor‐Yamada‐Nakanishi‐Niino (MYNN) scheme were closer to those recorded at the meteorological stations.  相似文献   

从理念到行动：温室气体与局地污染物减排的协同效益与协同控制研究综述     

毛显强  曾桉  邢有凯  高玉冰  何峰 《气候变化研究进展》2021,17(3):255-267

自20世纪90年代IPCC提出协同效益概念以来,大量研究充分证实了温室气体减排政策、措施能产生可观的局地生态环境质量和健康效益。相应地,既有研究也证实局地大气污染物减排政策、措施对温室气体减排同样具有协同效益。中国进入工业化成熟期不久,局地大气污染压力即达到峰值,又迎头遭遇国际应对气候变化浪潮,同时面临空气污染物与温室气体双重减排压力。因此,国内研究不仅关注“由碳及污”或“由污及碳”的单向协同效益评估,更加重视对综合减排措施的协同效益评价。21世纪初,美国国家环保局提出的温室气体与局地大气污染物协同控制概念在中国得到更为广泛的欢迎和接受,并由中国学者首先定义了协同控制的内涵,认为协同控制是实现最大化协同效益的手段和途径。这一进展将人们对协同效益的认识提升到“全球视野、局地行动”的新高度,推动人们从被动地接受“协同效益”,转而主动寻求“协同控制”温室气体和局地大气污染物,为统筹全球和国内（局地）两个减排战场,提供了从认识论、方法论到实践论的全方位支持。中国学者在国内外协同效益、协同控制研究基础上,构建协同控制效应评价和协同控制路径规划方法,并通过多个行业、城市、区域的案例研究证实了该方法体系的科学性和可行性。“协同控制”也已上升成为国家应对气候变化和持续改善大气环境质量的重要策略。在中国推进美丽中国建设、实现碳达峰目标和碳中和愿景的过程中,协同控制的理念、措施、政策将发挥愈加重要的作用。未来,协同控制研究需要将所关注的对象要素,从仅局限于大气扩展至整个生态环境系统;而对建立协同控制的治理体系的研究,将成为实现宏观层面气候变化与生态环境治理协同的关键。  相似文献   

Strategies and tactics for local market making in the Temporary Staffing Industry     

《Geoforum》2016

This paper examines the increasing complexity of interactions between temporary staffing agencies and their client firms within the local labour market of Birmingham, UK. Temporary Staffing Agencies have been identified as active and influential agents in local, national and international labour markets. Their influence on local labour market functioning, national labour regulation and international regulatory frameworks is growing. Existing literature demonstrates the power of large multinational temporary staffing agencies in both established and emerging temporary staffing markets. Such analyses also contend that multinational agencies operate in very different ways to smaller independent ‘back-street’ temporary staffing agencies, with different types of clients and at different ends of the market. However, the research conducted in Birmingham, UK suggests that the reality is more complex. It is argued that there can be more subtle and intricate nuances of relevance to the temporary staffing industry in respect of the relationships that exist between large and small temporary staffing agencies, as well as between such agencies and their clients. We highlight how smaller agencies in Birmingham are utilising a variety of strategies and tactics to creatively ‘bolt-on’ to more formalised national agreements established by multinational agencies with their clients. Moreover, smaller agencies – in some instances – are able to exploit their knowledge of local labour markets to subvert, sabotage and/or infiltrate the activities of multinational agencies in increasingly astute ways. In turn, this generates a series of questions for understanding the nature of ‘market making’ associated with the temporary staffing industry more broadly.  相似文献   

长白山哈尔巴岭气象塔湍流局地相似性研究     

张惠彬  关彩虹  黄顺祥  王丙兰  胡非 《气象科学》2016,36(4):474-482

利用长白山脉哈尔巴岭气象塔高频率湍流梯度观测数据,分析了2007—2009年间2月和7月2 m、30 m和100 m 3个观测高度湍流统计特征,对复杂下垫面局地相似理论适用性进行了检验,求出了无量纲风速标准差、无量纲温度和湿度标准差与稳定度关系的经验公式,发现了该地域湍流统计特征的新现象。结果表明:(1)冬季和夏季对流条件下2 m、30 m和100 m高度上无量纲风速标准差与稳定度Z/L之间能较好的满足1/3幂律,但夏季能更好地满足1/3幂律,且变化趋势明显,而冬季变化趋势平缓,接近直线。通过和其他学者的研究结果进行比较,发现了一些差异。(2)冬季无量纲温度、湿度标准差观测值随稳定度分布十分离散,但总体变化趋势基本满足-1/3幂律,而夏季观测值分布集中,变化趋势较好地满足-1/3幂律,反映出该地域无量纲温度、湿度标准差与稳定度关系随季节变化十分明显,且夏季对流强于冬季。(3)在30 m和100 m高度上,摩擦速度具有明显的日变化,但2 m高度上摩擦速度的变化比较特异,出现了夜间高于日间的情况,通过研究三维风速的脉动资料,发现夜间的风速脉动资料明显偏大,是导致夜间摩擦速度u*取值较大的直接原因,这种现象的发生可能是由该地域地形效应和下垫面特征引起的。  相似文献   

夏季太湖局地气候效应的数值模拟研究   总被引：1，自引：1，他引：0  

唐滢  黄安宁  田栗嵘  孙慧  戚鹏达  沈沛丰 《气象科学》2016,36(5):647-654

利用WRF模式,通过数值模拟试验研究了夏季太湖的局地气候效应,揭示了太湖对局地降水、温度等气象要素的影响,并探讨了内在的物理机制。结果表明:太湖主要在局地尺度上引起夏季地面气温降低和降水的减少,影响强度从湖区向周边地区逐渐减弱;太湖引起的夏季降水减少主要来源于对对流性降水的减弱作用;太湖对湖区及邻近区域夏季地面气温和降水的影响表现出明显的日变化特征,白天影响程度明显强于夜间且在午后的影响最强;太湖在午后引起湖区及邻近地区低层大气显著降温和异常辐散,抑制了该区域的大气对流活动并引起对流降水的明显减少,进而造成夏季太湖及邻近地区降水的减少。  相似文献   

1990年代初夏季东北亚低压的年代际转变   总被引：1，自引：1，他引：0  

杜梦醒  林中达  陆日宇 《大气科学》2016,40(4):805-816

夏季东亚地区对流层低层受到一个陆地低压系统控制;该低压中心位于东亚的北部地区,文中称之为东北亚低压。基于NCEP/DOE、NCEP/NCAR、ERA-40和ERA-Interim四种不同的再分析数据,本文分析了夏季东北亚低压的年代际变化特征,并进一步探讨了其转变的可能物理机理。研究结果表明夏季东北亚低压在1990年代初期存在一次显著的年代际转变, 之后低压强度减弱。对应此次年代际转变,东北亚地区对流层位势高度呈现为正压结构的正异常,其南侧的高空西风急流中心强度减弱。进一步,基于观测和简单线性斜压模式模拟结果,我们提出环贝加尔湖地区夏季气温增加可能是导致1990年代初期之后夏季东北亚低压减弱的原因。  相似文献   

A locally conservative finite element framework for the simulation of coupled flow and reservoir geomechanics     

Birendra Jha  Ruben Juanes 《Acta Geotechnica》2007,2(3):139-153

In this paper, we present a computational framework for the simulation of coupled flow and reservoir geomechanics. The physical model is restricted to Biot’s theory of single-phase flow and linear poroelasticity, but is sufficiently general to be extended to multiphase flow problems and inelastic behavior. The distinctive technical aspects of our approach are: (1) the space discretization of the equations. The unknown variables are the pressure, the fluid velocity, and the rock displacements. We recognize that these variables are of very different nature, and need to be discretized differently. We propose a mixed finite element space discretization, which is stable, convergent, locally mass conservative, and employs a single computational grid. To ensure stability and robustness, we perform an implicit time integration of the fluid flow equations. (2) The strategies for the solution of the coupled system. We compare different solution strategies, including the fully coupled approach, the usual (conditionally stable) iteratively coupled approach, and a less common unconditionally stable sequential scheme. We show that the latter scheme corresponds to a modified block Jacobi method, which also enjoys improved convergence properties. This computational model has been implemented in an object-oriented reservoir simulator, whose modular design allows for further extensions and enhancements. We show several representative numerical simulations that illustrate the effectiveness of the approach.  相似文献   

Local tomography and focal mechanisms in the south-western Alps: Comparison of methods and tectonic implications     

Bthoux Nicole  Sue Christian  Paul Anne  Virieux Jean  Frchet Julien  Thouvenot Franois  Cattaneo Marco 《Tectonophysics》2007,432(1-4):1-19

We investigate how focal solutions and hypocenter locations may depend on the ray tracing algorithm and the strategy of velocity inversion. Using arrival times from a temporary seismological network in the south-western Alps, a local earthquake tomography has been performed by Paul et al. [Paul, A., Cattaneo, M., Thouvenot, F., Spallarossa, D., Béthoux, N., and Fréchet, J., 2001. A three-dimensional crustal velocity model of the south-western Alps from local earthquake tomography. J. Geophys. Res. 106, 19367–19390.] with the method developed by Thurber [Thurber, C.H., 1993. Local earthquake tomography: velocity and Vp/Vs-Theory, in Seismic Tomography: Theory and practice, Iyer, H.M., and Irahara eds., Chapman and Hall, New York, 563–583.]. Another inversion of the same data set is performed here using a different tomography code relying on a shooting paraxial method and cubic interpolation of velocities. The resulting images display the same main features, although Thurber's code appears to be more robust in regions with scarce ray coverage and strong velocity contrasts. Concerning hypocenter location in Piemont units, one major result is the concentration of hypocenters at the boundary between the mantle wedge of the Ivrea body and the European crust. Forty-six focal mechanisms are shown that were computed using both the take-off angles in the minimum 1-D model and in the 3-D velocity structures resulting from the two inversions. The sets of focal solutions are very similar, proving the reliability and the coherency of the focal solutions. The widespread extension in the core of the western Alps is confirmed whereas a few compressive solutions are found east of the Piemont units. These results constrain the sharp change of stress tensor and evidence a decoupling of strain beneath the east of Dora Maira massif up to beneath the north of Argentera massif. On a geodynamical point of view seismicity and focal mechanism distribution are compatible with the present day models published for the western Alps, where the major feature is the lithospheric thickening [Schmid, S.M., and Kissling, E., 2000. The arc of the western Alps in the light of geophysical data on deep crustal structure. Tectonics, 19, 62–85.], implying widespread extension in the core of the western Alps [Sue, C., Thouvenot, F., Fréchet, J., and Tricart, P., 1999. Widespread extension in the core of the western Alps revealed by earthquake analysis. J. Geophys. Res., 104, 25611–25622.]. However the existence of compressive events dealing at depth with the boundary of Ivrea body allows to postulate that this geological structure is still tectonically active. Even if field work has not shown this so far, the Insubric line appears to extend toward the south at depth, as a blind fault, and to play a key role in the dynamics of the south-western Alps.  相似文献   

The importance of crustal structure in explaining the observed uncertainties in ground motion estimation     

John Douglas  Hideo Aochi  Peter Suhadolc  Giovanni Costa 《Bulletin of Earthquake Engineering》2007,5(1):17-26

In this short article, the possible reduction in the standard deviation of empirical ground motion estimation equations through the modelling of the effect of crustal structure is assessed through the use of ground-motion simulations. Simulations are computed for different source-to-site distances, focal depths, focal mechanisms and for crustal models of the Pyrenees, the western Alps and the upper Rhine Graben. Through the method of equivalent hypocentral distance introduced by Douglas et al. [(2004) Bull Earthquake Eng 2(1): 75–99] to model the effect of crustal structure in empirical equations, the scatter associated with such equations derived using these simulated data could be reduced to zero if real-to-equivalent hypocentral distance mapping functions were derived for every combination of mechanism, depth and crustal structure present in the simulated dataset. This is, obviously, impractical. The relative importance of each parameter in affecting the decay of ground motions is assessed here. It is found that variation in focal depth is generally more important than the effect of crustal structure when deriving the real-to-equivalent hypocentral distance mapping functions. In addition, mechanism and magnitude do not have an important impact on the decay rate.  相似文献   

虚拟局域网技术在信息网络管理中的应用     

兰陵  哈斯高娃 《内陆地震》2006,20(1):88-92

根据新疆维吾尔自治区地震局局域网的现状和存在的问题,将虚拟局域网技术引用到新疆维吾尔自治区地震局局域网管理中,分析和讨论建立虚拟局域网的实现方法和实际意义,解决目前局域网存在的问题,从而提高局域网网络管理和网络服务质量。  相似文献