A Case Study Of An On-Ice Air Flow Over The Arctic Marginal Sea-Ice Zone

A case study of warm air advection over the Arctic marginalsea-ice zone is presented, based on aircraft observations with direct flux measurements carriedout in early spring, 1998. A shallow atmospheric boundary layer (ABL) was observed, which wasgradually cooling with distance downwind of the ice edge. This process was mainly connected with astrong stable stratification and downward turbulent heat fluxes of about 10–20 W m^-2, but wasalso due to radiative cooling. Two mesoscale models, one hydrostatic and the other non-hydrostatic,having different turbulence closures, were applied. Despite these fundamental differences betweenthe models, the results of both agreed well with the observed data. Various closure assumptions had amore crucial influence on the results than the differences between the models.Such an assumption was, for example,the parameterization of the surface roughness for momentum (z₀) and heat (z_T). This stronglyaffected the wind and temperature fields not only close to the surface but also within and abovethe temperature inversion layer. The best results were achieved using a formulation for z₀ that took intoaccount the form drag effect of sea-ice ridges together withz_T = 0.1z₀. The stability within theelevated inversion strongly depended on the minimum eddy diffusivity K_min. A simple ad hocparameterization seems applicable, where K_min is calculated as 0.005 timesthe neutral eddy diffusivity. Although the longwave radiative cooling was largest within the ABL, theapplication of a radiation scheme was less important there than above the ABL. This was related to theinteraction of the turbulent and radiative fluxes. To reproduce the strong inversion, it wasnecessary to use vertical and horizontal resolutions higher than those applied in most regional andlarge-scale atmospheric models.     

深圳海岸复杂地形气流与湍流特征的数值模拟

利用三维非静力能量闭合（Ｅ－ε）的边界层模式，以深圳海岸复杂地形进行了实际模拟。结果给出了该地区海陆风情形下气流和湍流孤变化特征。在海风发展盛期，气流方向由大面积的水域和内陆的位置决定，不规则海岸线对局地气流影响不大，夜间陆风时，不规则海岸线对局地气流影响较大，湍流能量高值颁在陆地上空的不稳定层内，水面上湍能很小。模拟结果与实测结果上比较吻合。     

AN EVALUATION OF SEVERAL TURBULENCE SCHEMES FOR THE PREDICTION OF MEAN AND TURBULENT FIELDS IN COMPLEX TERRAIN

A prognostic three-dimensional mesoscale model has been developed andused in one- and two-dimensional modes to evaluate ten local turbulenceclosure schemes. The schemes ranged from first-order to the two-equationprognostic schemes. Predictions by the models were compared for aone-dimensional convective boundary layer using mixed layer scaling andmeasurements to interpret the results. Two-dimensional simulations were alsoperformed for a sea-breeze flow and for flow over a hill. The results showedthat for all of the models considered, minor differences were produced in themean meteorological fields and in the vertical scalar fluxes, but majordifferences were apparent in the velocity variances and dissipation rate.Predicted tracer concentrations were very sensitive to the turbulence modelformulation for dispersion from a point source in the convective boundarylayer, particularly for the prediction of maximum concentrations. Predictedtracer concentrations from a surface volume source for the two-dimensionalsimulations were similar for all models, although the degree of mixing in themorning growth period produced some differences. Generally, good results forthe mean meteorological fields can be obtained with first-order schemes, evenif they underpredict the magnitude of turbulence in the convective boundarylayer, and reasonable tracer concentrations can also be obtained with thesemodels provided near-source effects are not important. The two-equationprognostic models performed best for the prediction of turbulence in theconvective boundary layer.     

Turbulent fluxes over inhomogeneous landscape

Mesoscale surface turbulent fluxes over a complex terrain surrounded by oceans have been investigated using a 3-D numerical mesoscale model, under conditions with and without synoptic flows. The study indicated that under synoptically calm condition, the allocation and intensity of mesoscale surface turbulent fluxes (MSTFs) were greatly impacted by the thermally forced mesoscale circulation (TFMC) over mesoscale heterogeneous landscape. The max-imum values of sensible (Hs) and latent (LE) heat fluxes were located over the convergent zones and considerably im-pacted by the soil wetness (M), but did not depend strongly on the atmospheric background thermal stability (β0). The simulated results suggested that the sensible heat flux was closely proportional to the square of wind speed in the surface layer. By the action of synoptic flow, the allocation of LE was shifted to downwind, its intensity increased.     

用GMS卫星资料反演复杂地形下的降水率

强降水主要由生命史短的中小尺度天气系统造成,对此类天气系统的预报,目前只有依靠卫星和雷达的实时监测并结合中系统的概念模式外推来完成。由于中国西北地区地形极为复杂,造成雷达盲区,影响其估算降水率。因此采用GMS-4卫星的红外和可见光展宽云图资料,经处理并转换后,再加入相应网格点上的数字化地形高度资料作为因子之一,用多级逐步判别模式估算逐时雨强等级,最后形成一套可在微机上对雨强场进行图像显示及处理的软件系统,满足了现时预报的需要。结果表明,小雨以上的降雨区域不论面积、形状均与实况基本一致。     

闽浙沿海火山岩地区银矿成矿规律

本根据闽浙沿海火山岩地区银矿成矿规律和成矿预测的研究及近年来的矿产勘查，成矿预测和专科研成果，综合论述了闽浙沿海火山岩地区银矿的成矿地质条件，矿床类型和矿床特征，分析和总结了银矿的成矿规律和成矿作用，建立了区域成矿模式和成矿系列，同时指出，火山热液充填充代型银矿是本区最重要、也是最普遍的成因类型，并阐明了找矿方向。     

中国火山岩地区金的成矿环境及分布规律

中国是一个火山岩广泛分布的国家，火山岩区的金矿不论其数量和储量在全国均占有重要地位，根据金和火山活动的关系，可划分出６种金矿类型，它们主要分布在６个火山岩区中，不同地区金的成矿作用各有其特色，总体可概括出７条成矿特征，这对于在我国广阔的火山岩区寻找金矿具有重要的指导意义。     

二维地电条件下充电法地形改正的一种方法

本文首先讨论了充电法地形改正方法及存在的问题，提出了一种基于比值法思想的地改方法，经理论模型验算表明，有较好的地改效果     

Numerical modeling of 3-D terrain effect on MT field

Using the boundary element method, the numerical modeling problem of three-dimensional terrain effect on magnetotelluric (MT) field is solved. This modeling technique can be run on PC in the case of adopting special net division. The result of modeling test for 2-D terrain by this modeling technique is basically coincident with that by 2-D modeling technique, but there is a great difference between the results of 3-D and 2-D modeling for 3-D terrain. Project supported by the National Natural Science Foundation of China.     

俄罗斯远东金属矿床形成条件的古地球动力学分析

根据本区地质构造的新资料,提出了区域板块构造模型。研究了从俯冲到加利福尼亚型转换和由后者又到俯冲的古地球动力学环境更替的意义。这种更替发生在对本区最重要的中—新生代历史时期,对区域成矿带整体乃至一些金属矿床的形成具有重要影响。论证了一些地体性质,尤其是俯冲-增生杂岩对矿床形成的重要意义。