Radiative effects on torrential rainfall during the landfall of Typhoon Fitow (2013)

Cloud microphysical and rainfall responses to radiative processes are examined through analysis of cloud-resolving model sensitivity experiments of Typhoon Fitow(2013) during landfall.The budget analysis shows that the increase in the mean rainfall caused by the exclusion of radiative effects of water clouds corresponds to the decrease in accretion of raindrops by cloud ice in the presence of radiative effects of ice clouds,but the rainfall is insensitive to radiative effects of water clouds in the absence of radiative effects of ice clouds.The increases in the mean rainfall resulting from the removal of radiative effects of ice clouds correspond to the enhanced net condensation.The increases(decreases) in maximum rainfall caused by the exclusion of radiative effects of water clouds in the presence(absence) of radiative effects of ice clouds,or the removal of radiative effects of ice clouds in the presence(absence) of radiative effects of water clouds,correspond mainly to the enhancements(reductions) in net condensation.The mean rain rate is a product of rain intensity and fractional rainfall coverage.The radiation-induced difference in the mean rain rate is related to the difference in rain intensity.The radiation-induced difference in the maximum rain rate is associated with the difference in the fractional coverage of maximum rainfall.     

机器学习法在面向对象影像分类中的对比分析

针对如何选择遥感影像面向地理对象分类方法的问题,该文面向地理国情普查中的地表覆盖分类应用,以3个典型区域(山区、平原、城区)的多源高分辨率遥感影像为实验数据,从分类效果、分类精度等方面对比分析3种分类方法(支持向量机、决策树、随机森林)的优劣。在相同影像分割、特征提取、样本采集条件下,通过333组分类实验,得出以下规律:支持向量机分类方法稳定性强,分类速度快,但对特征数的要求高,特征数目与总体精度、地物环境之间的规律性不强,从而增加了特征提取与选择的难度,而随着特征的增加,决策树、随机森林的总体分类精度均为先升高后降低,最后趋于平衡。最后,综合随机森林对特征的优选机制和支持向量机的高分类精度,得到新的组合分类器。     

城市地理空间数据集成应用探讨

城市地理空间数据是表达城市地理要素的数量、质量、分布特征、相互关系、变化规律的位置信息和属性信息。分析城市地理空间数据的组成结构、组织管理、集成利用,并将这些数据有效应用于城市地理信息系统建设之中,将在城市信息化道路上起到举足轻重的作用。该文以开发的"兰州市城关区地理信息集成系统"为例,重点阐述了城市地理空间数据的构成与获取方式,研究了城市地理空间数据与业务部门数据的集成方法,并对城市地理空间数据在晕渲图制作、三维景观生成、数据可视化等主要应用上进行了分析和探讨。     

WRF模式中QNSE方案的湍流长度尺度系数的调整试验研究

边界层参数化方案中湍流混合对数值模拟起着重要的作用,湍流混合作用的恰当描述对于温度、湿度、风场以及降水的准确模拟至关重要。我国长江中下游流域人口密集,暴雨灾害频发,很有必要寻找一种适合该地区降水模拟的边界层参数化方案。本文运用WRF（Weather Research and Forecasting）中尺度数值模式,以QNSE（Quasi-Normal Scale Elimination）边界层参数化方案为基础,将其中湍流混合长度尺度系数调整为可变参数。本文将Noh et al.（2003）提出的Prandtl公式与Janji?提出的修正湍流长度尺度系数的方法相结合,通过考虑非局地项的强迫、地表稳定度与边界层高度对湍流长度尺度系数的影响,强调大气的动力结构特征与热力结构特征对湍流混合的共同影响,从而提高QNSE边界层参数化方案在不同地理环境下的模拟能力。文章通过进行长江中下游地区的典型暴雨试验,将调整参数后的QNSE方案与原方案进行比较,重点分析调整参数后的方案与原方案对关键基本气象要素场、边界层结构特征以及降水的模拟能力,并将模拟结果与观测结果进行对比,结果表明:调整参数后的方案一定程度上改进了地表温度、边界层结构以及降水的模拟效果。进一步研究表明,调整参数后的方案主要通过改变边界层混合缓解水汽混合比、位温模拟方面的误差。     

顾及轨道误差BDS/GPS实时钟差融合估计的观测权函数设计

实时钟差产品是高精度广域差分位置服务(亚米级、分米级、厘米级)的基础产品,本文针对BDS/GPS轨道精度差异,设计了一种顾及轨道精度差异观测权函数,优化了实时钟差估计的随机模型,在此基础上基于非差法实现了BDS/GPS联合的实时钟差估计。采用MGEX和iGMAS跟踪站的实时观测数据进行实时钟差解算,并与iGMAS产品综合中心提供的事后精密钟差产品进行了比较分析。结果表明:基于该方法估计的钟差精度对单GPS、单BDS和BDS/GPS融合都有提高,其中BDS钟差精度整体较GPS更为显著,提高幅度约12.8%,其中IGSO/MEO更为突出,提高幅度约20%,验证了方法的有效性。     

混合智能优化算法的SAR图像特征选择

为提高SAR图像自动目标识别的准确率及实时性,提出了一种基于混合智能优化的SAR图像特征选择算法。首先,采用分形特征对SAR图像进行增强,基于分割后的图像提出了一种基于图像矩的方位角估计方法。然后基于未校正和校正后的图像分别提取Zernike矩、Gabor小波系数和灰度共生矩阵构成候选特征集合,使用遗传算法结合二值粒子群的混合优化算法实现SAR图像特征选择。最后,采用MSTAR数据库验证本文算法的有效性。实验结果表明,优化后的特征集合具有一定泛化能力,一方面提高了SAR目标识别的准确率,另一方面减小了SAR图像目标识别的时间。     

气象卫星发展回顾与展望

回顾了国际气象卫星和中国风云气象卫星的发展,综述了气象卫星在图像解译、定量产品应用和数据同化方面的成就以及辐射校正技术的进步。围绕大气科学,特别是数值天气预报对天基观测的需求,展望了未来气象卫星的技术发展方向。     

Spatio-Temporal Characteristics of Heavy Precipitation Forecasts fromECMWF in Eastern China

This study examines the spatio-temporal characteristics of heavy precipitation forecasts in eastern China fromthe European Centre for Medium-Range Weather Forecasts (ECMWF) using the time-domain version of the Method forObject-based Diagnostic Evaluation (MODE-TD). A total of 23 heavy rainfall cases occurring between 2018 and 2021 areselected for analysis. Using Typhoon “Rumbia” as a case study, the paper illustrates how the MODE-TD method assessesthe overall simulation capability of models for the life history of precipitation systems. The results of multiple tests withdifferent parameter configurations reveal that the model underestimates the number of objects’ forecasted precipitationtracks, particularly at smaller radii. Additionally, the analysis based on centroid offset and area ratio tests for differentclassified precipitation objects indicates that the model performs better in predicting large-area, fast-moving, and long lifespan precipitation objects. Conversely, it tends to have less accurate predictions for small-area, slow-moving, and short lifespan precipitation objects. In terms of temporal characteristics, the model overestimates the forecasted movement speedfor precipitation objects with small-area, slow movement, or both long and short lifespans while underestimating it forprecipitation with fast movement. In terms of temporal characteristics, the model tends to overestimate the forecastedmovement speed for precipitation objects with small-area, slow movement, or both long and short lifespans while un derestimating it for precipitation with fast movement. Overall, the model provides more accurate predictions for theduration and dissipation of precipitation objects with large-area or long-lifespan (such as typhoon precipitation) whilehaving large prediction errors for precipitation objects with small-area or short-lifespan. Furthermore, the model’s simu lation results regarding the generation of precipitation objects show that it performs relatively well in simulating thegeneration of large-area and fast-moving precipitation objects. However, there are significant differences in the forecastedgeneration of small-area and slow-moving precipitation objects after 9 hours.     

海绵铁对活性艳红K-2BP废水的脱色动力学研究

为了开发新型的脱色填料,进行海绵铁对活性艳红K-2BP的脱色动力学研究。试验结果表明,海绵铁对活性艳红K-2BP具有较高的脱色率,在10min,30min和60min脱色率分别为58.78%,85.2%和93.89%。在海绵铁表面衰减分析的基础上,建立了脱色动力学模型,并研究了pH值、温度、粒径和投加量对反应速度常数K和表面衰减系数Ka的影响。