多尺度耦合经验正交分解法反演海洋次表层温盐结构

针对提升利用卫星观测海面信息重构三维温盐场精度的问题, 本文提出了一种基于多尺度耦合正交分解的三维温盐场重构方法。该方法利用多尺度耦合正交分解对历史温盐剖面进行从大尺度到小尺度的迭代分解, 以分层提取不同尺度三维温盐场的特征信息, 然后分别建立海洋表面卫星观测与不同尺度的三维温盐场特征信息的重构模型, 从而达到三维温盐场重构的目的。本文分别利用多尺度耦合正交分解法与单层正交分解法进行三维温盐场重构, 结果显示, 多尺度耦合正交分解优于单层正交分解法, 且随着分解的层次不断细化, 重构温盐场的精度及其垂直梯度精度均呈现明显的提升, 其中组合4精度提升程度最高, 分别提升了25.57%和27.58%; 同时, 对比HYCOM模式数据, 多尺度耦合正交分解重构方法能有效地捕捉次表层海洋的空间特征信息。总体上, 本文耦合经验正交分解法反演的温盐场与Argo温盐场偏差较小, 反演精度较好, 在空间分布上趋于一致。     

江淮梅雨期(6-7月)最高气温的区域特征

利用江淮地区64个测站1961-2001年6-7月最高气温资料，采用旋转经验正交展开(REOF)方法对江淮地区梅雨期最高气温场进行客观分区，并分析了各区域最高气温的长期演变趋势。结果表明：江淮地区梅雨期最高气温场可分为3个区域。各区域的最高气温均具有明显的年代际变化特征，且存在着显著差异，其中东南区长期变化趋势不明显，而北方区和西南区显著降低；各区域存在明显不同的年际、年代际方差构成和多尺度振荡周期。     

估计SURE模型参数的一种方法探讨

提出了计算ＳＵＲＥ（ＳｅｅｍｉｎｇｌｙＵｎｒｅｌａｔｅｄＲｅｇｒｅｓｓｉｏｎＥｑｕａｔｉｏｎｓ－表面无关回归方程）模型参数的一种方法,利用正交变换,以避免在直接计算方差－协方差逆矩阵（或其估计）时,经常导致的不必要的精度损失的困难,较详细地考虑了特殊的ＳＵＲＥ模型的求解过程,在这里,每个方程回归变量集中包含前面方程的回归变量作为当前回归变量集的适当子集。     

近40年我国降水量年际变化的区域性特征

应用方差极大准则下的正文旋转因子分析，对我国近４０年标准化年降水量场序列进行客观区划。结果表明，全国降水量场可明显划分成十大区域，它们各自具有不同的旱涝变化特征。例如，华北区和黄河中上游区变干趋势最为显著；西北地区和淮河、长江中上游地区略有变湿；而长江中下游、东北及珠江流域、华南沿海地区长期趋势呈波动变化．８０年代年降水量略低于５ｏ年代。     

基于非线性正交回归模型预测城市建设用地量

采用非线性正交回归模型(NORM),以GDP、固定资产投资、消费品零售额为主要影响因子,预测天津市塘沽区2006-2010年建设用地量和土地供应量,并分析了塘沽区土地资源利用规律及趋势。预测到2010年,低、高经济运行模式下塘沽区建设用地量分别为93.64 km2和93.98 km2,置信区间分别为±15.79 km2和±15.80 km2;2010年低、高经济运行模式下土地供应量分别为227.58 km2和207.85 km2,分别是同期建设用地量的242%和221%。2005—2009年塘沽区高经济运行模式下建设用地量高于低经济运行模式下建设用地量,2010年后高、低经济运行模式下建设用地量和土地供应量接近,经济发展对土地资源的依赖逐渐减弱,土地资源利用渐趋规范、合理、有序。     

Seasonal Evolution of Dominant Modes in South Pacific SST and Relationship with ENSO

A season-reliant empirical orthogonal function(S-EOF) analysis was applied to the seasonal mean SST anomalies(SSTAs) based on the HadISST1 dataset with linear trend removed at every grid point in the South Pacific(60.5-19.5 S,139.5 E-60.5 W) during the period 1979-2009.The spatiotemporal characteristics of the dominant modes and their relationships with ENSO were analyzed.The results show that there are two seasonally evolving dominant modes of SSTAs in the South Pacific with interannual and interdecadal variations;they account for nearly 40% of the total variance.Although the seasonal evolution of spatial patterns of the first S-EOF mode(S-EOF1) did not show remarkable propagation,it decays with season remarkably.The second S-EOF mode(S-EOF2) showed significant seasonal evolution and intensified with season,with distinct characteristics of eastward propagation of the negative SSTAs in southern New Zealand and positive SSTAs southeast of Australia.Both of these two modes have significant relationships with ENSO.These two modes correspond to the post-ENSO and ENSO turnabout years,respectively.The SEOF1 mode associated with the decay of the eastern Pacific(EP) and the central Pacific(CP) types of ENSO exhibited a more significant relationship with the EP/CP type of El Nin o than that with the EP/CP type of La Nin a.The S-EOF2 mode contacted with the EP type of El Nin o changing into the EP/CP type of La Nin a showed a more significant connection with the EP/CP type of La Nin a.     

The Effects of Vegetation Density on Coherent Turbulent Structures within the Canopy Sublayer: A Large-Eddy Simulation Study

Large-eddy simulation has become an important tool for the study of the atmospheric boundary layer. However, since large-eddy simulation does not simulate small scales, which do interact to some degree with large scales, and does not explicitly resolve the viscous sublayer, it is reasonable to ask if these limitations affect significantly the ability of large-eddy simulation to simulate large-scale coherent structures. This issue is investigated here through the analysis of simulated coherent structures with the proper orthogonal decomposition technique. We compare large-eddy simulation of the atmospheric boundary layer with direct numerical simulation of channel flow. Despite the differences of the two flow types it is expected that the atmospheric boundary layer should exhibit similar structures as those in the channel flow, since these large-scale coherent structures arise from the same primary instability generated by the interaction of the mean flow with the wall surface in both flows. It is shown here that several important similarities are present in the two simulations: (i) coherent structures in the spanwise-vertical plane consist of a strong ejection between a pair of counter-rotating vortices; (ii) each vortex in the pair is inclined from the wall in the spanwise direction with a tilt angle of approximately 45°; (iii) the vortex pair curves up in the streamwise direction. Overall, this comparison adds further confidence in the ability of large-eddy simulation to produce large-scale structures even when wall models are used. Truncated reconstruction of instantaneous turbulent fields is carried out, testing the ability of the proper orthogonal decomposition technique to approximate the original turbulent field with only a few of the most important eigenmodes. It is observed that the proper orthogonal decomposition reconstructs the turbulent kinetic energy more efficiently than the vorticity.     

用经验正交函数构造武汉地区电子浓度总含量的经验模式

本文利用经验正交函数（Empirical Orthogonal Function, 简称EOF）分析了武汉电离层台站一个太阳黑子周期（1980年4月～1990年12月）的实测电离层电子浓度总含量（TEC）资料,在此基础上构建了一个武汉地区的TEC月中值的经验模式.结果表明：（1）以EOF分析观测数据具有一定的物理意义,其基函数表征TEC的日变化,系数表征TEC的长期变化;（2）EOF技术展开收敛速度快,很少数低阶项即能反映TEC的主要变化,采用经验正交函数建模可以用较少的参数表征较复杂的物理过程.此外,本文还就TEC模式的外部驱动量的改进问题作了一些探讨,发现用F107A（107cm太阳辐射通量F107的81天滑动平均值）作TEC建模的外部驱动量能够更好地提高EOF模式的精度和稳定性.     

基于正交小波变换的并行软判决盲均衡算法

针对常数模算法收敛速度慢的缺点,在分析基于正交小波变换盲均衡器结构和并行软判决盲均衡算法的基础上,提出一种基于正交小波变换的并行软判决盲均衡算法.该算法将正交小波变换引入到并行软判决算法中,利用正交小波变换对信号很强的去相关能力,降低信号的自相关性,以加快算法的收敛速度.水声信道仿真结果表明,与并行的软判决盲均衡算法相比,所提出的基于正交小波变换的并行软判决盲均衡算法具有更快的收敛速度.     

中国1960-2016年风能资源的时空分布特征

基于462个气象观测站1960–2016年共57年的近地面风速日资料,利用克里格空间内插,最小二乘法,相关系数检验和经验正交函数分解(EOF)等方法分析了年均和各个季节中国区域风速及有效风能密度的时空变化特征。研究结果表明:在中国北部和部分沿海地区年平均风速在3 m s-1以上,有效风能密度在75 W m-2以上,而在中国南部地区平均风速和有效风能密度均较小。近五十多年以来,中国区域年均和季节平均风速呈明显下降趋势,北部地区春季递减率最大,沿海地区冬季递减率最大。广东部分地区年平均风速有增大的趋势,西南,华南和华中西部地区年平均风速变化不大。平均风速大的区域,递减率也大。年平均风速和年有效风能密度的主要空间分布模态表现出高度的一致性,均呈现逐年减小趋势。中国风速及风能资源的减小趋势,主要与全球变暖及土地利用变化有关。