Pre-summer Persistent Heavy Rain over Southern China and Its Relationship with Intra-seasonal Oscillation of Tropical Atmosphere     

邱迪  姚素香  夏依聪 《热带气象学报(英文版)》2022,28(4):445-456

Based on daily precipitation data supplied by the Chinese meteorological administration, hourly reanalysis datasets provided by the ECMWF and daily outgoing long wave radiation supplied by the NOAA, the evolution regularity of continuous heavy precipitation over Southern China (SC) from April to June in 1979-2020 was systematically analyzed. The interaction between specific humidity and circulation field at the background-scale, the intra-seasonal-scale and the synoptic-scale, and its influence on persistent heavy precipitation over the SC during the April-June rainy season were quantitatively diagnosed and analyzed. The results are as follows. Persistent heavy rainfall events (PHREs) over the SC during the April-June rainy season occur frequently from mid-May to mid - and late-June, exhibiting significant intra-seasonal oscillation (10-30-day) features. Vertically integrated moisture flux convergence (VIMFC) can well represent the variation of the PHREs. A multiscale quantitative diagnosis of the VIMFC shows that the pre-summer PHREs over the SC are mainly affected by the background water vapor (greater than 30 days), intra-seasonal circulation disturbance (10-30-day) and background circulation (greater than 30 days), and water vapor convergences are the main factor. The SC is under the control of a warm and humid background and a strong intra-seasonal cyclonic circulation, with strong convergence and ascending movements and abundant water vapor conditions during the period of the PHREs. Meanwhile, the westward inter-seasonal oscillation of tropical atmosphere keeps the precipitation system over the SC for several consecutive days, eventually leading to the occurrence, development and persistence of heavy precipitation.  相似文献   

中文文本蕴含气象灾害事件信息多模型融合抽取方法     

胡段牧  袁武  牛方曲  袁文  韩嫒嫒 《地球信息科学学报》2022,24(12):2342-2355

随着气候变暖加剧,全球极端天气事件频发,重大气象灾害的发生频率与日俱增。研究气候变化与气象灾害发生频率的关系,对于气候变化背景下的防灾减灾具有重要意义。文献资料及泛在网络数据中蕴含了海量的气象灾害时空事件,为此,本文基于自然语言处理技术研发了文本气象灾害时空事件自动抽取方法。① 提出了基于专业文献的由粗到精的气象灾害标注语料训练库构建方法。首先针对不同文献资料存在的歧义和不兼容等问题,构建了面向文本事件统一的气象灾害知识体系。然后构建了基于章节结构的粗标注方法,分别针对长文本（现代文）和短文本（文言文）研发了基于Labeled LDA模型及基于TF-IDF和N-gram模型的精细标注语料筛选方法,解决了语料库的快速构建问题;② 基于BERT-CNN模型研发了融合上下文语义特征和多粒度的局部语义特征的、面向长短文本一体化处理的气象灾害时空事件自动分类方法;③ 利用该方法分别从文言文和泛在网络数据中自动抽取了灾害时空事件,其宏F1值分别达到89.09%和80.06%,主要气象灾害时空事件分布与专业统计数据相关性较高;④ 基于以上结果,重建了我国各历史时期灾害时空演变过程,发现各时期灾害数据量整体呈现出逐步上升趋势,暴雨灾害、洪涝灾害与干旱灾害是影响我国的主要灾种。本方法既可实现网络长文本事件的自动发现,也可实现文言文短文本事件的自动检测,为文本数据便捷应用于气象灾害研究和监测提供了新的技术方法。  相似文献   

降水时间随机性对月总降水量的影响          下载免费PDF全文

苏京志 《大气科学学报》2019,42(1):109-116

降水量在时间分布上呈现较大的随机性,极端降水事件尤为如此。受此影响,月初(月末) 1～5 d之内的累积降水量很可能会超过当月总降水量的50%乃至更多。对1961—2017年中国2 400多站点资料统计分析结果发现,月初(月末) 1～5 d累积降水量对当月总降水量显著影响事件的出现频次,在季节和空间分布上都有鲜明特征。主要包括:1)月初累积降水量对秋冬季中各月的总降水量影响更大,月末累积降水量对1—4月的月总降水量影响较大。2)受月初累积降水量的影响,显著站点数在某些年份的某些月份出现极大值;受单次事件显著影响的站点数占全国总站点数的30%～50%,此即对应着一次全国大范围的极端降水事件。3)受月初(月末)累积降水量显著影响的站点空间分布随季节变化呈现出明显空间集聚特征。  相似文献   

基于GIS的山区村镇多灾种耦合风险评估     

王嘉君  何亚伯  杨琳  陈瑶 《中国地质灾害与防治学报》2018,29(1):102-112

为解决在山区村镇多灾种综合风险评估中忽略灾害间相互作用、对村镇防灾减灾规划指导缺乏的问题,提出基于GIS的多灾种耦合风险评估模型。本文以神农架林区为研究对象,选取山洪、泥石流和滑坡3种主要自然灾害为评价对象,从危险性、易损性两个方面,致灾因子、孕灾环境、承载体暴露性与敏感性、防灾减灾能力四个角度建立评价体系,基于ArcGIS 10.1空间分析技术进行多灾种风险耦合分析,利用风险矩阵完成综合评估。结果显示:神农架自然灾害风险高值区主要分布在林区西部和南部大部分地区、东北部局部地区。该模型提高了多灾种耦合风险评估的准确度、角度精度,改进后的模型具有较高的实用价值。  相似文献   

塔东北库鲁克塔格地区震旦-奥陶纪地质事件及生储盖组合          下载免费PDF全文

赵明胜  田景春  苏炳睿  张翔 《中国地质》2018,45(3):591-603

塔里木盆地库鲁克塔格地区是重要的油气资源战略接替区域之一,其特殊的构造背景成为研究盆山耦合及区域构造演化的有效切入点。冰川、火山、风暴、浊流等事件沉积的产物,广泛发育于塔东北库鲁克塔格地区震旦—奥陶系的地层中。这些地质事件的发生时期与库鲁克塔格地区的构造演化具有明显的耦合关系。Rodinia超大陆的裂解是全球新元古代冰川沉积的诱发因素,也使库鲁克塔格地区在震旦纪发育冰川相的沉积。发生于早寒武世的火山事件也是Rodinia超大陆同期裂解的表现。在塔东北地区,裂解导致的持续拉张作用一直延续到早奥陶世末期,但在晚寒武世曾发生过一次持续时间较短的构造反转,区域构造应力场由拉张转为挤压,导致南、北沉积相区水体变浅,受到风暴作用影响。在挤压的区域构造背景下,中—晚奥陶世库鲁克塔格急剧隆升,物源供给的加大,为浊流事件的沉积提供了有利条件。另外,区域的构造背景变化也对于该地区的源岩和储层的产生起了决定性的因素。在震旦—早奥陶世晚期拉张的大地构造背景下,早—中寒武世及早奥陶世成为烃源岩的主要形成时期。优质储层主要为碳酸盐岩及碎屑岩,发育于晚震旦世、晚寒武世、中—晚奥陶世。孔隙类型主要为晶间孔、溶孔、裂缝等。这些源岩和储层与地层中的泥岩在垂向上组成多套生储盖组合。  相似文献   

Simulating regional grain yield distributions to support agricultural drought risk assessment     

《Applied geography (Sevenoaks, England)》2015

Most food insecure countries do not have long-term records of either agricultural drought or the impacts of agricultural drought on food security. This lack of data impedes famine early warning and crop insurance programs. One recent paper addresses this issue by using resampled rainfall data, a basic crop yield model, and linear regression to simulate distributions of grain yield. We expand on this process by incorporating flexible regression models and defining a set of criteria to test model performance. We also examine how well a model fit on national data can emulate yield distributions at regions within a country. We find that models with spatially varying coefficients are better able to simulate distributions than basic linear regression models. Generalized additive models also perform well but do not offer substantial improvement over varying coefficient models. We also find that simulated yield distributions are most accurate in higher producing regions that have lower within region diversity of yields.  相似文献   

海南冬种瓜菜气象灾害风险评估与区划     

张蕾  霍治国  黄大鹏  姜燕  肖晶晶 《地理研究》2015,34(2):293-305

基于自然灾害风险理论,利用海南省18个站点气象资料、瓜菜生产和社会经济要素资料,通过灾情反演,构建苗期湿涝、冬季寒害和春季干旱致灾等级指标。综合致灾、孕灾、灾损、防灾能力,进行瓜菜气象灾害的综合风险分析与区划。结果表明:苗期湿涝危险性从西南至东北增加,春季干旱危险性东西高、中间低;西瓜寒害危险性从中部向两边减小,豇豆和丝瓜寒害危险性从南往北加重,辣椒寒害危险性从东南到西北增加;苗期湿涝孕灾环境敏感性从中部山区向沿海和平原地区增加,春季干旱和冬季寒害趋势相反;瓜菜灾损风险和防灾能力在区域上存在明显差异;西瓜、豇豆和辣椒气象灾害综合风险总体趋势一致,高风险区集中在海南东部地区;丝瓜气象灾害综合风险高值区在北部地区。  相似文献   

Projects,people, professions: Trajectories of learning through a mega-event (the London 2012 case)     

《Geoforum》2015

Planning and organization of large-scale events such as Olympic Games are accomplished by several specialized project organizations, in charge of securing finances, completing the infrastructures, negotiating with multiple stake-holders and the day-to-day management of the actual event. These organizations have to cope with a key challenge. Due to their inherently temporary nature they cannot provide the specialized knowledge and specific “project capabilities” (Davies and Brady) on their own, but have to mobilize them from the past and from outside their boundaries, e.g. from previous events or other mega-projects in the host city. Rather than in permanent organizations, then, the knowledge on preparing and performing mega-events is primarily sedimented and embodied in professionals.Drawing on the planning and organization of the London Olympics 2012 as empirical case, the paper addresses, on the one hand, this particular mobilization process. On the other, it looks at how this process is intertwined with three different trajectories that both affect and are affected by the mega-event: the trajectory of the project that aims to recruit necessary skills; the trajectory of individual persons who perceive working for the Olympics as a rewarding episode in their careers; the trajectory of professional communities that expect learning benefits for the construction and project management industry in the UK.  相似文献   

Geochemical characteristics of Holocene aeolian deposits and their environmental significance in the Mu Us Desert,northern China     

Bing Liu  He‐Ling Jin  Liang‐Ying Sun  Zhong Sun  Qing‐He Niu  Cai‐Xia Zhang 《Geological Journal》2016,51(3):325-337

This paper addresses the surface and Holocene aeolian deposits in the southeastern Mu Us Desert, N. China, systematically analysing the evolution of the geochemical characteristics of aeolian sand–palaeosol sequences and their environmental significance. Our results indicate that the geochemical components of the Holocene aeolian deposits and surface deposits had the similar material sources, sediment transport and deposition processes in the study region, which were dominated by SiO₂, Al₂O₃, and Na₂O. In the weathering process of the Jinjie (JJ) profile, the Na, K, and Si presented the slight leaching and migration in general, while the other elements were relatively accumulated. The Holocene aeolian deposits and surface deposits incurred weaker geochemical weathering under cold and dry conditions and were only weakly leached, which implies a relatively arid environment in the Holocene epoch and the modern era. The weathering degree was controlled by the regional temperature and precipitation, and was probably more sensitive to the precipitation changes. In the sedimentary profile, the geochemical parameters and migration of elements demonstrated that there have been several alternating warm–wet and cold–dry intervals in the Mu Us Desert in the Holocene epoch; there were relatively warm and wet conditions prior to 4.6 ka, and it has been cold and dry since then. Six millennial‐scale dry events were recorded during the Holocene, which were not only accordant with the history of palaeoclimatic changes in the different latitudes and archives of the Northern Hemisphere, but also correspond to the millennial‐scale variation of cosmic radiation and solar activity during that period. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

2001-2012年新疆融雪型洪水时空分布特征   总被引：4，自引：3，他引：1  

阿不力米提江·阿布力克木  陈春艳  玉素甫·阿不都拉  巴哈古丽·瓦哈甫 《冰川冻土》2015,37(1):226-232

利用2001-2012年新疆区域内发生的融雪型洪水资料,分析研究了近12 a新疆融雪型洪水时空分布特征.结果表明:新疆融雪型洪水与前一年10月至当年3月新疆全站总累计降水量大小相关,降水量大的年份,对应的融雪型洪水发生次数也多;冬末至夏季融雪型洪水在北疆地区基本上是从西向东、从南向北的先后顺序出现,而在南疆地区的融雪洪水基本上是从西向东、从北向南先后顺序出现.新疆融雪型洪水主要集中出现在春夏季,其中,北疆地区在3月,南疆地区在7月发生较多;伊犁河谷、昌吉、阿勒泰、和田等地区及青河、乌鲁木齐、阿克陶、民丰等市县是新疆融雪型洪水的高发区.  相似文献