欧亚冬季雪盖对北半球夏季大气环流的影响及其与东亚太平洋型遥相 …

利用ＮＯＡＡ的欧亚大陆冬月平均雪盖面积资料和中国气象局的北半球夏季５００ｈＰａ高度场资料进行统计分析,发现欧亚大陆冬了雪盖面积异常可以激发北半球夏季积雪强迫型遥相关,它具有显著的准４年周期,在准４年时间尺度上,建立了积雪强迫型遥相关和东亚太平洋型遥相关的可能联系,推测了准４年循环中的可有作用过程。     

气候变化2007:气候变化影响、适应和脆弱性——IPCC第2工作组第4次评估报告主要结论介绍

阐述了政府间气候变化专门委员会(IPCC)第2工作组第四次评估中与决策相关的重要发现。本次评估体现了当前关于气候变化对自然、管理和人类系统的影响、这些系统的适应能力及脆弱性方面的科学认识。该评估基于此前IPCC的评估,并吸收了第3次评估以来的新认识。评估报告认为:从所有大陆和多数海洋得到的观测证据表明,许多自然系统正在受到区域气候变化,特别是温度升高的影响;人为增暖可能已对许多自然和生物系统产生可辨别的影响;气候变化对自然和人类环境所造成的其他影响清晰可辨。当前关于未来气候变化影响的认识,可以更详细地评估未来气候对各类系统和部门,以及对世界各大区域的影响,也可以对全球升温的影响进行估算,预估极端天气气候所带来的影响。必须采取更广泛的适应措施以应对气候变化所造成的影响,可持续发展能够降低对气候变化的脆弱性,兼顾适应和减缓的措施,能够减低气候变化相关风险。     

CORRECTION OF ASYMMETRIC STRENGTHENING OF QUIKSCAT WIND FIELD AND ASSIMILATION APPLICATION IN TYPHOON SIMULATION

As an approach to the technological problem that the wind data of QuikSCAT scatterometer cannot accurately describe the zone of typhoon-level strong wind speed, some objective factors such as the typhoon moving speed, direction and friction are introduced in this study to construct the asymmetric strengthening of the QuikSCAT wind field. Then by adopting a technology of four-dimensional data assimilation, an experiment that includes both the assimilation and forecasting phases is designed to simulate Typhoon Rananim numerically. The results show that with model constraints and adjustment, this technology can incorporate the QuikSCAT wind data to the entire column of the model atmosphere, improve greatly the simulating effects of the whole-column wind, pressure field and the track as well as the simulated typhoon intensity covered by the forecast phase, and work positively for the forecasting of landfall locations.     

使用卫星资料进行边界层四维变分同化研究综述

数值天气预报是当前天气预报的重要手段之一,而同化工作一直是数值预报研究的重点。在查阅了近年来国内外相关文献的基础上,对使用卫星举行资料边界层四维变分同化的研究进展进行了论述,并对最优插值法和变分法2种主要的研究方法进行了简单介绍。研究结果认为,变分方法对于初始场的改善具有明显的效果,与纯粹的统计插值方法相比,变分法具有十分明显的优势;理论上变分法能够同化所有类型大气探测资料,对非常规探测的包容能力极强,不仅能最大限度地获得观测中的信息量,而且避免了各种反演不适定问题。     

3维地学模拟与虚拟矿山系统

3维地学模拟（3D Geoscience Modelling，简称3DGM）与虚拟矿山系统（Virtual Mine System，简称VMS）是数字矿山（Digital Mine，简称DM）战略实施的关键技术，其中3DGM是VMS及所有真3维地学虚拟现实系统的基础。基于国内外VMS研究与应用分析，指出目前2．5维VMS的缺陷和不足；同时，对当前国际学术界3DGM理论与方法进行了评析。进而，从3DGM与VMS耦合的角度出发，提出了一种新的3DGM方法：类三棱柱（Analogic Tri-Prism，简称ATP）法。ATP模型由点、TIN边、TIN面、棱边、侧面TIN和ATP体共6组基本元素组成。本文设计了ATP的数据结构，并给出了基于实验钻孔的3DGM可视化图。     

The Structure of Background-error Covariance in a Four-dimensional Variational Data Assimilation System: Single-point Experiment

A four dimensional variational data assimilation (4DVar) based on a dimension-reduced projection (DRP-4DVar) has been developed as a hybrid of the 4DVar and Ensemble Kalman filter (EnKF) concepts. Its good flow-dependent features are demonstrated in single-point experiments through comparisons with adjoint-based 4DVar and three-dimensional variational data (3DVar) assimilations using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5). The results reveal that DRP-4DVar can reasonably generate a background error covariance matrix (simply B-matrix) during the assimilation window from an initial estimation using a number of initial condition dependent historical forecast samples. In contrast, flow-dependence in the B-matrix of MM5 4DVar is barely detectable. It is argued that use of diagonal estimation in the B-matrix of the MM5 4DVar method at the initial time leads to this failure. The experiments also show that the increments produced by DRP-4DVar are anisotropic and no longer symmetric with respect to observation location due to the effects of the weather trends captured in its B-matrix. This differs from the MM5 3DVar which does not consider the influence of heterogeneous forcing on the correlation structure of the B-matrix, a condition that is realistic for many situations. Thus, the MM5 3DVar assimilation could only present an isotropic and homogeneous structure in its increments.     

An Economical Approach to Four-dimensional Variational Data Assimilation

Four-dimensional variational data assimilation (4DVar) is one of the most promising methods to provide optimal analysis for numerical weather prediction (NWP). Five national NWP centers in the world have successfully applied 4DVar methods in their global NWPs, thanks to the increment method and adjoint technique. However, the application of 4DVar is still limited by the computer resources available at many NWP centers and research institutes. It is essential, therefore, to further reduce the computational cost of 4DVar. Here, an economical approach to implement 4DVar is proposed, using the technique of dimension-reduced projection (DRP), which is called ``DRP-4DVar." The proposed approach is based on dimension reduction using an ensemble of historical samples to define a subspace. It directly obtains an optimal solution in the reduced space by fitting observations with historical time series generated by the model to form consistent forecast states, and therefore does not require implementation of the adjoint of tangent linear approximation. To evaluate the performance of the DRP-4DVar on assimilating different types of mesoscale observations, some observing system simulation experiments are conducted using MM5 and a comparison is made between adjoint-based 4DVar and DRP-4DVar using a 6-hour assimilation window.     

云迹风在热带气旋路径数值预报中的应用研究

通过一系列四维变分同化试验对GMS5卫星资料反演的云迹风资料在西北太平洋热带气旋的初始化及路径数值预报中的作用进行研究,同化资料为中国国家卫星气象中心提供的GMS5水汽和红外云迹风资料,其中70%在400hPa以上,50%集中在200～300hPa。应用美国NCAR/PSU中尺度模式MM5及其四维变分同化系统,同化窗口为6h,对初始时刻和6h后的云迹风进行同化。同化前对云迹风资料进行了简单的类似ECMWF初值检验方法的质量控制。对2002年8个西北太平洋热带气旋共进行了22组试验。结果表明,采用四维变分同化技术同化云迹风对热带气旋路径预报有一定改善,12,24,36和48h预报的平均距离误差分别降低5%,12%,10%和7%,但同化云迹风的作用与初始气旋强度有关。选择初始中心海平面气压960hPa作为强、弱气旋的分类标准,则11个较强气旋平均路径误差12h减小了13%,12h以后的预报误差减小率维持在20%以上。而对于11个较弱气旋,平均路径误差反而略有增加,说明同化云迹风资料对不同初始强度的气旋作用也有所不同。其主要原因是由于强度较强的热带气旋往往具有较为深厚的垂直结构,因此受高层大气流场的影响更明显;同时,较弱热带气旋的云迹风观测相对稀少且凌乱,并且更容易受环境气流的影响,因此对于较弱的热带气旋,当模式变量与模式或变量之间在同化后不够协调的话,就会产生负效应。     

基于四维灾体模型的浙江省气象灾害损失年景评价

应用浙江省气象灾情统计年鉴资料,运用四维灾体评估模型,对浙江省的气象灾害损失进行科学评估。浙江省2003—2017年灾害损失年景评价分析结果显示,2004年和2005年为气象灾害损失明显偏重年景,进入2010年以来,2013年为年景最差年份;台风灾害损失在每年浙江省气象灾害损失年景评价中具有非常重要的作用,重大台风事件易造成气象灾害偏重或明显偏重的损失年景。评估结果表明,四维灾体模型下的气象灾害评估较为科学客观。     

滩涂数字地形模型的建模与应用

采用数字高程模型描述上海市滩涂地形,研究和设计了数字高程模型的数据结构,较好地解决了海量数据的存储、查询和检索问题,由此建立了多年的滩涂数字地形模型。在此基础上研究了滩涂地形分析方法,并在地理信息系统平台上开发了滩涂地形分析系统。试用结果表明,该系统数据结构合理、功能齐全、运行快速稳定,较好地满足了滩涂海塘管理工作的需要。