夏季东海西部表层海水中的pCO₂及海-气界面通量   总被引：10，自引：0，他引：10  

谭燕  张龙军  王凡  胡敦欣 《海洋与湖沼》2004,35(3):239-245

根据2001年夏季长江口及东海西部海域表层海水pCO  相似文献   

Global thermal and dynamical perturbations due to Cretaceous mantle avalanche     

Philippe Machetel 《Comptes Rendus Geoscience》2003,335(1):91-97

The numerical models of mantle convection agree to depict avalanches behaviour according to the level of endothermicity of the spinel → perovskite phase change. Their potential effects on the global thermal and dynamical states of the mantle have been computed thanks to a numerical code, which takes into account both the 400-km exothermic and the 660-km endothermic phase changes. The cycle followed by the avalanches is: local layering, destabilization of the 660-km thermal layer, travelling and spreading on the core, and reappearing of the local layering. Therefore, mantle convection is characterized by quiet periods of partial layering embedded in catastrophic events. During the avalanche, the amplitude of the surface velocity is multiplied by two, which would imply an enhanced plate tectonic and ridge activities. The global thermal effects of the avalanche are compatible with a high mantle temperature and an acceleration of Earth's rotation during the Cretaceous. They also offer a coherent explanation to locate the origin of mantle plumes both within the CMB and just below the transition zone.  相似文献   

Turbulence Statistics Inside and Over Forest: Influence on Footprint Prediction   总被引：2，自引：0，他引：2  

Ü. Rannik  T. Markkanen  J. Raittila  P. Hari  T. Vesala 《Boundary-Layer Meteorology》2003,109(2):163-189

Observations of wind statistics within and above a Scots pine forest are comparedwith those predicted from an analytical second-order closure model. The roughnesssublayer (RSL) effects, and the influence of stability on similarity functions, arestudied using observations. The commonly accepted forms of similarity functionsdescribe the influence of diabatic effects above the RSL well. According to earlierstudies they are expected also to apply within the RSL. As an exception, the averagewind speed normalised with friction velocity was found to be invariant with stabilityclose to the canopy top under unstable conditions. Lagrangian stochastic trajectorysimulations were used to evaluate the influence of canopy turbulence profiles onfootprint prediction. The main uncertainty was found to arise from parameterisationof the random forcing term in the Lagrangian velocity equation. The influence ofdiabatic conditions was studied, and it was found that thermal stability affectssignificantly the footprint function above the forest canopy, but significantuncertainty exists because of uncertainties in the formulation of stability functions.  相似文献   

基于通量距平的大气-海洋-海冰耦合模式   总被引：2，自引：0，他引：2  

张学洪  俞永强  金向泽  刘辉 《应用气象学报》1997,(Z1)

该文是对基于月平均通量距平（ＭＦＡ）的海气耦合方案及其在４个海气耦合的环流模式中应用情况的一个综合评述．这些模式的实施情况表明，由于采用精细化了的参考通量，修正的ＭＦＡ（ＭＭＦＡ）比它的原型具有更为稳定的控制气候漂移的能力．  相似文献   

A Simple Parameterisation for Flux Footprint Predictions   总被引：9，自引：6，他引：9  

N. Kljun  P. Calanca  M. W. Rotach  H. P. Schmid 《Boundary-Layer Meteorology》2004,112(3):503-523

Flux footprint functions estimate the location and relative importance of passive scalar sources influencing flux measurements at a given receptor height. These footprint estimates strongly vary in size, depending on receptor height, atmospheric stability, and surface roughness. Reliable footprint calculations from, e.g., Lagrangian stochastic models or large-eddy simulations are computationally expensive and cannot readily be computed for long-term observational programs. To facilitate more accessible footprint estimates, a scaling procedure is introduced for flux footprint functions over a range of stratifications from convective to stable, and receptor heights ranging from near the surface to the middle of the boundary layer. It is shown that, when applying this scaling procedure, footprint estimates collapse to an ensemble of similar curves. A simple parameterisation for the scaled footprint estimates is presented. This parameterisation accounts for the influence of the roughness length on the footprint and allows for a quick but precise algebraic footprint estimation.  相似文献   

中国西部干旱地区太阳直接辐射通量密度与大气质量的关系   总被引：1，自引：0，他引：1  

王尧奇  韦志刚 《高原气象》1990,9(3):327-336

本文根据中国西部干旱地区大气物理状态(大气可降水量和大气浑浊度)的变化范围,利用太阳直接辐射通量密度的理论计算公式,计算了各种大气透明系数状况下的太阳直接辐射通量密度。计算结果表明,大气质量m=2时的透明系数P_2和m相同时,由于水汽和气溶胶的含量配置不同而引起太阳直接辐射通量密度的差异,在辐射日变程的主要时段(m=1-3)内并不大。于是得到各种透明系数P_2状况下太阳直接辐射通量密度随大气质量变化的平均关系。不同海拔高度比较,当透明系数P_2相同时,各自的大气物理状态虽然不同,但m相同时的太阳直接辐射通量密度基本相同。现有的表征太阳直接辐射通量密度值和大气质量联系的关系式都不能很好地描述计算结果。根据太阳直接辐射通量密度随大气质量变化的特性,我们提出了新的关系式。最后,整理了不同拔海高度和不同地理景观的四个日射站(西藏那曲、青海格尔木、甘肃敦煌和民勤)的多年观测资料。经验计算结果与观测值比较,一致性良好。  相似文献   

通量传输事件磁场的理论计算及其与观测的比较     

刘振兴  王德驹 《地球物理学报》1991,34(5):538-551

根据涡旋诱发重联理论,对通量传输事件（FTEs）磁场分布特性作了计算.结果表明,卫星测到的FTEs的不同磁场分布形态,是取决于通量管的运动方向及卫星穿越通量管的部位.在北半球,当通量管由低纬向高纬（由南向北）直向运动时,不论卫星通过什么部位,绝大多数情况下观测到先正后负的B_x,变化（即正FTE）,个别部位观测到先负后正的B_x变化（即反FTE）;B_z是单峰分布形式,表现为V型、倒V型或是U型和倒U型.当通量管在x方向有正或负速度分量即斜向运动时,大部分部位测到的B_x呈不规则变化,B_z表现为双极分布.与61个FTEs的观测实例作了对比,理论计算与观测符合得较好.  相似文献   

斜压半地转模式中的非频散周期解   总被引：2，自引：0，他引：2  

何建中  何金海 《热带气象学报》1994,10(1):57-63

给出了３个通量矢量，从而将非线性平流项表示为３个通量矢量的旋度和散度，它们分别对纬向风和经向风的低频加速产生贡献。经过卷积运算，还建立了低频变化的动力学模型。给出了通量矢量Ｅ．、Ｇ１．、Ｇ２．等的空间分布及其相应的流函数与势函数的水平分布和时间演变，从而指出，瞬变扰动间的相互作用对流动具有低频加速作用。  相似文献   

The harmonious character in equilibrium aeolian transport on mixed sand bed   总被引：1，自引：0，他引：1  

Mao Xing   《Geomorphology》2007,86(3-4):230-242

Wind tunnel experiments were carried out to measure the spatial distribution in equilibrium transport of four types of mixed sand. The flux profiles of each grain size group were calculated. It is found that the vertical distribution of mean grain size has a close relation with the grain size distribution in the sand bed. In a log-linear plot, the flux profiles of main grain size groups are all straight lines and their slopes are nearly equal. It is also found that the ratio of transport rate of each size group to the whole transport rate is directly proportional to the mass ratio of each size group in the sand bed and the proportion value is only dependent on the grain size. This harmonious law is applicable to all four types of mixed sand used in the experiment.  相似文献   

Energy Balance Of A Sparse Coniferous High-Latitude Forest Under Winter Conditions   总被引：1，自引：0，他引：1  

Sven-Erik Gryning  Ekaterina Batchvarova  H. A. R. De Bruin 《Boundary-Layer Meteorology》2001,99(3):465-488

Measurements carried out in Northern Finland on radiation and turbulent fluxes over a sparse, sub-arctic boreal forest with snow covered ground were analysed. The measurements represent late winter conditions characterised by low solar elevation angles. During the experiment (12–24 March 1997) day and night were about equally long. At low solar elevation angles the forest shades most of the snow surface. Therefore an important part of the radiation never reaches the snow surface but is absorbed by the forest. The sensible heat flux above the forest was fairly large, reaching more than 100 W m^-2. The measurements of sensible heat flux within and above the forest revealed that the sensible heat flux from the snow surface is negligible and the sensible heat flux above the forest stems from warming of the trees. A simple model for the surface energy balance of a sparse forest is presented. The model treats the diffuse and direct shortwave (solar) radiation separately. It introduces a factor that accounts for the shading of the ground at low solar elevation angles, and a parameter that deals with the partial transparency of the forest.Input to the model are the direct and diffuse incoming shortwave radiation.Measurements of the global radiation (direct plus diffuse incoming shortwaveradiation) above the forest revealed a considerable attenuation of the globalradiation at low solar elevation. A relation for the atmospheric turbidity asfunction of the solar elevation angle is suggested. The global radiation wassimulated for a three month period. For conditions with a cloud cover of lessthan 7 oktas good agreement between model predictions and measurementswere found. For cloud cover 7 and 8 oktas a considerable spread can beobserved. To apply the proposed energy balance model, the global radiationmust be separated into its diffuse and direct components. We propose a simpleempirical relationship between diffuse shortwave and global radiation asfunction of cloud cover.  相似文献