MM5模式水平扩散项的改进及其对陕西“8.28”暴雨模拟的影响

在数值预报发展的过程中,我们通常把水平扩散项当作滤波器用来光滑或是过滤掉模式积分过程中所产生的毫无天气意义的并会引起非线性计算不稳定的所谓计算噪音或“超短波”,从而达到阻尼虚假短波以及抑制非线性计算不稳定的目的,但这仅仅只是从计算数学或计算物理的角度来考虑,并不能真正反映扩散的物理本质。本文尝试运用热力学第二定律的思想对MM5模式中的水平扩散项进行改造,以便更好地消除原模式中的扩散项所导致的Gibbs振荡现象。通过对陕西2003年8月28日暴雨的数值模拟表明,改进后的MM5模式的输出量（如相对湿度、温度、速度）的相关系数以及均方根误差均有明显的改进。     

浙江省近百年气温变化研究

利用浙江省近百年气温等级资料，分析全省冬季、夏季和全年气温变化，发现浙江省年气温变化总趋势与北半球、全国比较一致，但年气温上升、下降的时间比北半球、全国年气温变化有滞后现象。冬季最低气温升高，是暖冬的主要特征，夏季极端最高气温天数明显减少，是凉夏的主要特征。     

利用重整化群方法讨论强震前地震活动的临界点现象

基于自组织和临界现象的基本现点，利用重整化群方法对７级以上强震前中小地震增强现象的临界点问题进行了探讨性的研究与讨论。得到的基本结论有：一些７级以上强震前存在中小地震临界点现象，超过临界点后将发生强震；重整化群方法在中期预报中有着广阔的应用前景。     

NUMERICAL SIMULATION OF TROPICAL CYCLONE MOVEMENT WITH THE RELATED CRITICAL POINT PHENOMENON*

A study is made of the paths of tropical cyclones under the joint action of environmental flow and heating fields in terms of a quasi-geostrophic barotropic model with the thermal forcing and dissipation terms involved,in which 16 experiments are designed and integrated for more than 7 model days.Results show that for different parameter values of the environmental flow and heating field,and the cyclone scale,such paths as counterclockwise looping,zigzag form and westward march with an abrupt turning towards the north are reproduced clearly in the model atmosphere,exhibiting their critical points of nonlinear character.     

一种顾及驱动因子重要性的双约束RF-Patch-CA城市扩张模拟方法

城市扩张模拟为实现土地资源合理分配与制定城市发展规划政策提供依据。该文针对传统元胞自动机(CA)在城市扩张模拟中存在城市元胞密集区域团簇现象,耦合随机森林(RF)与基于斑块(Patch)扩张的CA模型,在顾及驱动因子重要性基础上构建基于斑块最大面积和城市扩张总量的双约束RF-Patch-CA模型,并利用该模型模拟重庆主城都市区2010-2017年城市扩张。结果显示:该模型总体精度达97.62%,相比传统的RF-CA、ANN-CA和Logistic-CA模型,Kappa系数分别提高了0.0222、0.0231和0.0245,FoM分别提高了0.0376、0.0391和0.0414;在景观相似度上,该模型相比以上3种模型分别提高了40.92%、41.16%和32.33%,最接近真实情况,而且避免了模拟结果产生城市元胞团簇现象,有效提高了城市扩张模拟精度。     

雨滴谱降水现象仪综合测试系统设计

针对目前国内对雨滴谱降水现象自动观测仪常用标定方法存在的问题:只能模拟一种标准的粒子直径和速度;可以测量粒子的直径但是不能准确测量粒子的速度;只能模拟直径较小的粒子;仅能模拟球状降水粒子无法模拟其他形状的降水粒子;无法涵盖各种类型降水的粒子直径和速度等等。根据气象业务需求,本文从模拟降水粒子设计依据、雨滴谱降水现象仪综合测试系统构成、降水粒子直径与下落速度模拟测量方法和测量精度等诸方面详细阐述一种新型的雨滴谱降水现象仪综合测试系统,并通过对涵盖多种类型降水的不同直径和速度的粒子进行模拟试验,检测其测量的精确性,为国内对雨滴谱降水现象自动观测仪的标定和检测提供一定的借鉴和参考。     

“Ghost cities” identification using multi-source remote sensing datasets: A case study in Yangtze River Delta

Drastic urbanization has taken place in China during the last two decades. Recently, a considerable number of “ghost cities” have emerged due to the extensive and unreasonable urban expansion which far exceeds the practical demand. In order to investigate “ghost cities”, we proposed a feasible framework by utilizing multi-source remote sensing datasets, including nighttime light imagery, land cover type products and population grid. After eliminating blooming effect of nighttime imagery by a proposed modified optimal threshold method (MOTM) and extracting built-up area from land cover type products, we developed a “ghost city” index (GCI) to quantify and evaluate the intensity of “ghost city” phenomenon in Yangtze River Delta at county/district level. The GCI was established according to the intrinsic features of “ghost cities”, comprising three criteria: consistency of lit area and built-up area, illumination intensity and population density. Then, we explored the spatial pattern of “ghost cities” of different GCI categories and the ternary contour was applied to demonstrate the key factor among three criteria. Our finding implies that “ghost cities” are prominently spatial clustered. Meanwhile, counties and new development zones have higher risk of suffering from the phenomenon, while capital cities and municipal cities have an alleviative effect for ambient regions. Besides, regions with higher intensity of the phenomenon tend to have less balanced composition among three criteria. Our results show good consistency with previous reports and studies, providing a more objective and spatial explicit insight into the “ghost city” phenomenon. Our findings do not only prove the capability of monitoring “ghost cities” using remote sensing data, but would also be beneficial to urban planning and regional sustainable development.     

HY-WP1A天气现象视频智能观测仪的业务运行和日常维护

天气现象视频智能观测仪投入业务试运行以来,较好的解决了云、地面凝结现象、雪等天气现象(气象要素)的自动化观测。但是该仪器的结构复杂、参数设置较多、维护要求较高,需要业务人员具有较强的理论知识和动手能力。本文通过从仪器结构、工作原理、安装要求、业务运行等方面对该仪器进行了介绍,让业务人员更加了解天气现象视频智能观测仪的使用,对相关故障排查提供技术支撑。     

旅游地网络口碑再传播影响因素

关注旅游网络口碑的扩散现象、掌握网络环境下旅游口碑的再传播规律是旅游地及相关企业实现病毒式网络营销的关键。通过对收集到的982份有效问卷进行因子分析以归纳旅游地网络口碑再传播的因子,并通过逐步回归分析法探讨影响旅游地网络口碑人际再传播和群体再传播的具体因素。结果表明:对人际再传播有显著影响的因素是口碑趣味性、网站可信度、关系强度以及再传播者的帮助他人动机和知识自我效能动机;对群体再传播有显著影响的因素是关系强度以及再传播者的帮助他人动机、帮助网站动机、自我提升动机和知识自我效能动机。最后提出针对性的旅游地营销策略。     

网络文本数据时空感知计算概念、方法及应用场景

网络文本数据作为网络传感数据的一种,因其包含大量的时空信息,以及丰富的语义信息,不仅能够用于研究社会问题的时空特征,也能够对社会现象的时空规律提供语义上的可解释性,因此存在一定的应用价值,目前已逐渐得到研究者的关注。本文提出了网络文本数据的一般概念表示,分析了网络文本数据的类型和特征,重点梳理了网络文本数据时空感知计算的计算方法,总结了文本优先+地理背景和地理优先+文本增强两种计算模式,并从静态到动态、场景到区域的视角总结了4个相关应用场景。