对中尺度遥感资料进行四维同化的共轭方法及其数值研究

本文探讨了数值天气预报过程中对非定时观测的常规遥感气象资料进行四维同化，形成预报初始场的新途径，把数值预报初始场的形成提为数学上的一类反问题，运用数值模式及其共轭方程对象气资料进行变分同化的共轭方法，使众多观测资料的四维同化与时变的动力模型在初始场的形成过程中统一考察，克服了以往一些方法的局限性，从理论和数值角度证明该方法的可行性，表明该方法有可能作为发展一个新的初值方案的雏形，有潜在的应用价值。     

植被措施与路面汇水对三峡库区土质道路边坡侵蚀影响

研究土质道路边坡在自然恢复、草本、草灌结合及植生带等4种不同植被恢复模式下的降雨侵蚀特征,同时将模拟降雨试验和冲刷试验相结合,研究路面汇水的介入对路堤边坡侵蚀的影响。研究结果表明,在模拟降雨试验下,草灌结合控制路堑边坡侵蚀效果最佳,产流量和产沙量显著低于其他植被模式;草本和草灌结合在路堤边坡降雨和冲刷下,都有显著的截流拦沙能力,且两种措施防护效果相当;路面来水的介入对路堤边坡侵蚀有显著促进作用,加速产流,增加产流量和产沙量。山区道路侵蚀的治理,不但要因地制宜地选择适宜的防护措施,更应该对路面产流和路面汇流进行科学合理的规划,减少其对路面及路堤的冲刷侵蚀。     

Transcriptome analysis elucidates key changes of pleon in the process of carcinization

When megalopa molting to the first juvenile crab stage, the crabs undergo carcinization morphogenesis. To study the key physiological and morphological processe...     

A Methodological Study on Using Weather Research and Forecasting(WRF) Model Outputs to Drive a One-Dimensional Cloud Model简

A new method for driving a One-Dimensional Stratiform Cold （1DSC） cloud model with Weather Research and Fore casting （WRF） model outputs was developed by conducting numerical experiments for a typical large-scale stratiform rainfall event that took place on 4-5 July 2004 in Changchun, China. Sensitivity test results suggested that, with hydrometeor pro files extracted from the WRF outputs as the initial input, and with continuous updating of soundings and vertical velocities （including downdraft） derived from the WRF model, the new WRF-driven 1DSC modeling system （WRF-1DSC） was able to successfully reproduce both the generation and dissipation processes of the precipitation event. The simulated rainfall intensity showed a time-lag behind that observed, which could have been caused by simulation errors of soundings, vertical velocities and hydrometeor profiles in the WRF output. Taking into consideration the simulated and observed movement path of the precipitation system, a nearby grid point was found to possess more accurate environmental fields in terms of their similarity to those observed in Changchun Station. Using profiles from this nearby grid point, WRF-1DSC was able to repro duce a realistic precipitation pattern. This study demonstrates that 1D cloud-seeding models do indeed have the potential to predict realistic precipitation patterns when properly driven by accurate atmospheric profiles derived from a regional short range forecasting system, This opens a novel and important approach to developing an ensemble-based rain enhancement prediction and operation system under a probabilistic framework concept.     

Characteristics and Numerical Simulations of Extremely Large Atmospheric Boundary-layer Heights over an Arid Region in North-west China

Over arid regions in north-west China, the atmospheric boundary layer can be extremely high during daytime in late spring and summer. For instance, the depth of the observed convective boundary layer can exceed 3,000 m or even be up to 4,000 m at some stations. In order to characterize the atmospheric boundary-layer (ABL) conditions and to understand the mechanisms that produce such an extreme boundary-layer height, an advanced research version of the community weather research and forecasting numerical model (WRF) is employed to simulate observed extreme boundary-layer heights in May 2000. The ability of the WRF model in simulating the atmospheric boundary layer over arid areas is evaluated. Several key parameters that contribute to the extremely deep boundary layer are identified through sensitivity experiments, and it is found that the WRF model is able to capture characteristics of the observed deep atmospheric boundary layer. Results demonstrate the influence of soil moisture and surface albedo on the simulation of the extremely deep boundary layer. In addition, the choice of land-surface model and forecast lead times also plays a role in the accurate numerical simulation of the ABL height.     

Simulations of Microphysics and Precipitation in a Stratiform Cloud Case over Northern China:Comparison of Two Microphysics Schemes

Using the Weather Research and Forecasting(WRF) model with two different microphysics schemes, the Predicted Particle Properties(P3) and the Morrison double-moment parameterizations, we simulated a stratiform rainfall event on20–21 April 2010. The simulation output was compared with precipitation and aircraft observations. The aircraft-observed moderate-rimed dendrites and plates indicated that riming contributed significantly to ice particle growth at the mature precipitation stage. Observation...     

Ensemble-based Kalman filters in strongly nonlinear dynamics

This study examines the effectiveness of ensemble Kalman filters in data assimilation with the strongly nonlinear dynamics of the Lorenz-63 model, and in particular their use in predicting the regime transition that occurs when the model jumps from one basin of attraction to the other. Four configurations of the ensemble-based Kalman filtering data assimilation techniques, including the ensemble Kalman filter, ensemble adjustment Kalman filter, ensemble square root filter and ensemble transform Kalman filter, are evaluated with their ability in predicting the regime transition (also called phase transition) and also are compared in terms of their sensitivity to both observational and sampling errors. The sensitivity of each ensemble-based filter to the size of the ensemble is also examined.     

空-谱信息与稀疏表示相结合的高光谱遥感影像分类

针对传统的高光谱遥感影像分类中多依赖光谱信息而忽视空间信息以及提取的特征维数高的问题,提出了一种空-谱信息与稀疏表示相结合的分类算法。首先,利用最小噪声分离对原始影像进行降维,在此基础上,对主成分图上局部影像块内的所有像素进行重组,并用排序的方法得到旋转不变的空-谱特征。然后,对空-谱特征进行监督学习得到字典,并将提取的测试样本的空-谱特征编码到字典中以得到测试样本的稀疏表示。最后,使用支持向量机分类器(SVM)对高光谱影像进行分类。3组高光谱数据试验表明,与传统的分类方法比较,本文方法能有效提高分类精度。     

颅内结核CT诊断(附10例分析)

目的　探讨　颅内结核常见征象及少见征象的ＣＴ表现以提高对本病的认识。材料与方法头颅ＣＴ平扫与增强扫描并随访１０例患者在临床上的愈合情况。结果１０例患者行抗痨治疗后好转或康复。结论ＣＴ能对颅内结核病作出准确的诊断。     

Numerical Simulation of the Rapid Intensification of Hurricane Katrina(2005):Sensitivity to Boundary Layer Parameterization Schemes

Accurate forecasting of the intensity changes of hurricanes is an important yet challenging problem in numerical weather prediction. The rapid intensification of Hurricane Katrina(2005) before its landfall in the southern US is studied with the Advanced Research version of the WRF(Weather Research and Forecasting) model. The sensitivity of numerical simulations to two popular planetary boundary layer(PBL) schemes, the Mellor–Yamada–Janjic(MYJ) and the Yonsei University(YSU) schemes, is investigated. It is found that, compared with the YSU simulation, the simulation with the MYJ scheme produces better track and intensity evolution, better vortex structure, and more accurate landfall time and location. Large discrepancies(e.g.,over 10 hPa in simulated minimum sea level pressure) are found between the two simulations during the rapid intensification period. Further diagnosis indicates that stronger surface fluxes and vertical mixing in the PBL from the simulation with the MYJ scheme lead to enhanced air–sea interaction, which helps generate more realistic simulations of the rapid intensification process. Overall, the results from this study suggest that improved representation of surface fluxes and vertical mixing in the PBL is essential for accurate prediction of hurricane intensity changes.