辅助模型辨识方法(1):自回归输出误差系统

研究了自回归输出误差(AR-OE)系统的辅助模型随机梯度算法、辅助模型多新息随机梯度算法、辅助模型递推最小二乘算法,自回归输出误差自回归滑动平均(AR-OEARMA)系统(即AR-Box-Jenkins系统)的辅助模型广义增广随机梯度算法、辅助模型多新息广义增广随机梯度算法、辅助模型递推广义增广最小二乘算法,以及AR-Box-Jenkins系统的基于滤波的辅助模型广义增广随机梯度算法、基于滤波的辅助模型多新息广义增广随机梯度算法、基于滤波的辅助模型递推广义增广最小二乘算法等.     

沈阳都市圈的范围及城镇空间分布的分形研究

科学界定都市圈范围是研究都市圈的基础,采用2014年沈阳市及周边市县镇乡社会经济统计数据,采用断裂点和经济隶属度模型,界定沈阳都市圈范围。用经济隶属度指标划分城镇体系。用分形理论分析沈阳都市圈城镇的空间分布特征,结果为：集聚维数、容量维数、信息维数和关系维数分别为1.430 1、1.294 1、1.473 5和0.393 8,说明沈阳都市圈城镇空间向心性集聚分布较为显著,城镇空间分布的均衡性较好,城镇空间分布具有较强的相关性,形成了以沈阳市为中心呈凝聚态分布的都市圈城镇空间结构,城镇间联系较为紧密,相互作用较强。进而提出沈阳都市圈城镇空间分布优化的对策。     

基于A-Train卫星编队资料的热带气旋强度估算

准确估算热带气旋(TC)强度,对于预测TC发展、减少财产损失具有重要的意义。前人将TC看作满足静力平衡和梯度风平衡的轴对称涡旋系统,基于云顶高度、云顶温度、海表面气压等物理量建立了TC强度估算模型,该模型未考虑环境垂直风切变对TC强度的影响。本文提出一种修正模型,通过统计拟合手段将垂直风切变加入原模型中。从2006—2015年的Cloud Sat资料中筛选出穿心个例共63个。针对云雷达(CPR)数据特点,提出根据反射率因子的垂直分布确定眼墙和外围边界位置的方法。分别用原模型与修正模型对这63个TC个例进行强度估算。与最佳路径数据相比,原模型结果总体偏大,尤其对风切变较大、强度较小的个例估算效果不佳。修正模型对于风切变大于5 m·s~(-1)的个例误差明显减小,平均绝对误差MAE、均方根误差RMSE和平均绝对误差百分比MAPE分别从5.8 m·s~(-1)、7.7 m·s~(-1)和19.5%变为3.5 m·s~(-1)、4.9 m·s~(-1)和11.5%。在一定强度范围内,修正模型估算效果随着强度的增强而提升。修正模型对于成熟阶段的个例效果更好,北半球的估算精度高于南半球,纬度越高,估算误差越小。试验结果表明,用该修正模型估算TC强度是可行的,可以对现有的技术进行辅助和补充。     

上海大气湿度的城、郊对比分析

本文通过对１９８４－１９９０年上海城区１１个气象站和近郊４个县气象站逐月平均水汽压及对１９８４年１、４、７、１０等４个月逐日０２、０８、１４、２０时等４个观测时刻气象观测资料的对比分析结合上海城市下垫面特征，阐明上海“城市”这个人为因子对大气湿度（水汽压ｅ）的影响，发现在年、月水汽压平均值上均是城区ｅｕ小于郊区ｅｒ，但在１、４、７、１０等月逐日４个观测时刻水汽压的城、郊水汽压差值△ｅｕ－ｒ上，却出     

复杂多通道带乘性噪声系统的最优固定域平滑算法

研究 1种在更弱的乘性噪声限制条件下系统的状态最优估计算法。在最优滤波算法的基础上 ,进一步给出了在线性最小方差意义下最优的固定域平滑算法。针对该算法所进行的仿真研究已表明该算法的有效性     

Near-shore swell estimation from a global wind-wave model: Spectral process,linear, and artificial neural network models

Estimation of swell conditions in coastal regions is important for a variety of public, government, and research applications. Driving a model of the near-shore wave transformation from an offshore global swell model such as NOAA WaveWatch3 is an economical means to arrive at swell size estimates at particular locations of interest. Recently, some work (e.g. Browne et al. [Browne, M., Strauss, D., Castelle, B., Blumenstein, M., Tomlinson, R., 2006. Local swell estimation and prediction from a global wind-wave model. IEEE Geoscience and Remote Sensing Letters 3 (4), 462–466.]) has examined an artificial neural network (ANN) based, empirical approach to wave estimation. Here, we provide a comprehensive evaluation of two data driven approaches to estimating waves near-shore (linear and ANN), and also contrast these with a more traditional spectral wave simulation model (SWAN). Performance was assessed on data gathered from a total of 17 near-shore locations, with heterogenous geography and bathymetry, around the continent of Australia over a 7 month period. It was found that the ANNs out-performed SWAN and the non-linear architecture consistently out-performed the linear method. Variability in performance and differential performance with regard to geographical location could largely be explained in terms of the underlying complexity of the local wave transformation.     

Estimation of boundary values in a North Atlantic circulation model using an adjoint method

A 1° × 1° resolution version of the MIT-GCM in the North Atlantic is used to test whether open-boundary conditions can be constrained by observations inside the domain using an adjoint method. In this preliminary feasibility study, the model is run during 1993 with a simplified vertical mixing physics. It is constrained by monthly SST fields, monthly climatological θ, S fields and TOPEX/POSEIDON altimetry. The adjoint model is built using automatic differentiation software. The method aims at bringing the model’s trajectory to consistency with data, by adjusting the initial θ, S fields, the time-varying atmospheric forcing fields and the time-varying open-boundary values. An originality of the work is the ‘nested approach’, which uses optimized fields from a global, coarser resolution model for the open-boundary conditions and for the prior estimates of the surface conditions adjustments. A solution is obtained after 75 iterations. This study shows that significant changes can be obtained on the open-boundary values, and that a general improvement in the circulation is achieved in the constrained solution, mainly in the Gulf Stream and equatorial regions. Changes at the open boundaries are characterized by a large temporal variability and small spatial scales. Large local adjustments are found close to the bottom and are likely unrealistic. There, the method tends to compensate for some model’s deficiencies by computing large corrections on the open-boundary values. The analysis of the cost function gradients with respect to the controls allows us to explore the local consistency between the constraints from the different data sets. This study suggests that no fundamental difficulty emerges when constraining open-boundary values. Its extension to a longer run with complete mixing physics can be envisaged.