2016年北京地区一次雷暴大风的观测研究   总被引：2，自引：2，他引：0  

程月星  孙继松  戴高菊  张慧洁 《气象》2018,44(12):1529-1541

利用常规气象观测资料、风廓线资料、北京观象台多普勒天气雷达产品、多普勒雷达变分同化分析系统（VDRAS）的反演资料和地面自动气象站客观分析资料,对2016年7月27日北京地区出现的一次雷暴大风天气的环境条件特征、风暴结构特征及演变机制进行了分析。结果显示：本次雷暴大风天气过程出现在弱天气尺度强迫环境中,较好的热力不稳定增强机制促使线状对流发展为弓形回波,形成雷暴大风天气。探空曲线中低层接近于干绝热的环境温度直减率和下沉对流有效位能突增等现象,对预报大风天气有较好的指示意义。上游雷暴的冷池出流与山前偏南暖湿气流在北京西部形成了明显的风向辐合,在强烈的扰动温度梯度和地形抬升的共同作用下,位于地面辐合抬升最强处触发新生单体并迅速发展。新生单体与风暴主体合并下山过程中,由于地形作用抬升了冷池出流高度,与平原地区偏南暖湿气流形成显著的不稳定层结,产生显著的扰动温度梯度,触发不稳定能量使雷暴在下山过程中强度增强。多普勒雷达产品上也表现为强的反射率因子核,并出现回波悬垂和有界弱回波区等特征,速度产品上可看到一对明显的端点涡旋。在冷池不断加强和端点涡旋对后入气流不断加速的共同作用下,后侧入流气流加强成为后侧入流急流,在低仰角速度产品上表现为显著的大风区。后侧入流气流将环境中的干冷空气夹卷进入云体,通过蒸发作用产生负浮力,使冷空气加速下沉,加之降水粒子的拖曳作用,最终造成剧烈的地面大风。  相似文献   

Exploring the effects of drastic institutional and socio-economic changes on land system dynamics in Germany between 1883 and 2007     

《Global Environmental Change》2014

Long-term studies of land system change can help providing insights into the relative importance of underlying drivers of change. Here, we analyze land system change in Germany for the period 1883–2007 to trace the effect of drastic socio-economic and institutional changes on land system dynamics. Germany is an especially interesting case study due to fundamentally changing economic and institutional conditions: the two World Wars, the separation into East and West Germany, the accession to the European Union, and Germany's reunification. We employed the Human Appropriation of Net Primary Production (HANPP) framework to comprehensively study long-term land system dynamics in the context of these events. HANPP quantifies biomass harvests and land-use-related changes in ecosystem productivity. By comparing these flows to the potential productivity of ecosystems, HANPP allows to consistently assess land cover changes as well as changes in land use intensity. Our results show that biomass harvest steadily increased while productivity losses declined from 1883 to 2007, leading to a decline in HANPP from around 75%–65% of the potential productivity. At the same time, decreasing agricultural areas allowed for forest regrowth. Overall, land system change in Germany was surprisingly gradual, indicating high resilience to the drastic socio-economic and institutional shifts that occurred during the last 125 years. We found strikingly similar land system trajectories in East and West Germany during the time of separation (1945–1989), despite the contrasting institutional settings and economic paradigms. Conversely, the German reunification sparked a fundamental and rapid shift in former East Germany's land system, leading to altered levels of production, land use intensity and land use efficiency. Gradual and continuous land use intensification, a result of industrialization and economic optimization of land use, was the dominant trend throughout the observed period, apparently overruling socio-economic framework conditions and land use policies.  相似文献   

COMPARATIVE ANALYSIS OF THE INTENSIFYING AND WEAKENING LANDFALL TROPICAL CYCLONES DURING EXTRATROPICAL TRANSITION OVER CHINA   总被引：1，自引：1，他引：0  

李侃  徐海明 《热带气象学报(英文版)》2015,21(1):23-33

Based on the Tropical Cyclone(TC) Yearbooks data and JRA-25 reanalysis data from the Japan Meteorological Agency(JMA) during 1979-2008, dynamic composite analysis and computation of kinetic energy budget are used to study the intensifying and weakening TCs during Extratropical Transition over China. The TCI shows strong upper-level divergence, strengthened low-level convergence and significantly enhanced upward motion under the influence of strong upper-level troughs and high-level jets. The TCI is correspondingly intensified after Extratropical Transition(ET); TCW exhibits strong upper-level divergence, subdued low-level convergence and slightly enhanced upward motion under the influence of weak upper-level troughs and high-level jets. It then weakens after ET. The increase(decrease) of the generation of kinetic energy by divergence wind in TCI(TCW) at low level is one of the major reasons for TCI’s intensification(TCW’s weakening) after transformation. The generation of kinetic energy by divergence wind is closely related to the development of a low-level baroclinic frontal zone. The growth of the generation of kinetic energy by rotational wind in TCI at upper level is favorable for TCI’s maintenance, which is affected by strong upper-level troughs. The dissipation of the generation of kinetic energy by rotational wind in TCW at upper level is unfavorable for TCW’s maintenance, which is affected by weak upper-level troughs.  相似文献   

Sensitivity of tropical cyclone intensification to inner-core structure     

Xuyang Ge  Wei Xu  Shunwu Zhou 《大气科学进展》2015,32(10):1407-1418

In this study, the dependence of tropical cyclone (TC) development on the inner-core structure of the parent vortex is examined using a pair of idealized numerical simulations. It is found that the radial profile of inner-core relative vorticity may have a great impact on its subsequent development. For a system with a larger inner-core relative vorticity/inertial stability, the conversion ratio of the diabatic heating to kinetic energy is greater. Furthermore, the behavior of the convective vorticity eddies is likely modulated by the system-scale circulation. For a parent vortex with a relatively higher inner-core vorticity and larger negative radial vorticity gradient, convective eddy formation and radially inward propagation is promoted through vorticity segregation. This provides a greater potential for these small-scale convective cells to self-organize into a mesoscale inner-core structure in the TC. In turn, convectively induced diabatic heating that is close to the center, along with higher inertial stability, efficiently enhances system-scale secondary circulation. This study provides a solid basis for further research into how the initial structure of a TC influences storm dynamics and thermodynamics.  相似文献   

Land tenure and agricultural expansion in Latin America: The role of Indigenous Peoples’ and local communities’ forest rights     

《Global Environmental Change》2015

Agricultural expansion remains the most important proximate cause of tropical deforestation, while interactions between socio-economic, technological and institutional factors represent the fundamental drivers. Projected population increases could further raise the pressure on the remaining forests, unless agricultural intensification allows raising agricultural output without expanding agricultural areas. The purpose of this article is to understand the role of institutional factors in governing the intensification process towards the goal of preserving forests from agricultural pressures, with a focus on Indigenous Peoples’ and local communities’ rights to forests (as embedded in the various tenure regimes). In this paper we adopt an international dimension and analyse the process of agricultural expansion across eleven Latin American countries over the period 1990–2010 to assess whether, in a context of agricultural intensification, different land tenure regimes impact differently on the realization of land-sparing or Jevons paradox. The results, based on a number of multivariate statistical models that controls for socio-economic factors, strongly suggest that the formal recognition of Indigenous Peoples and local communities’ forest rights has played an important role in promoting land sparing or attenuating Jevons paradox.  相似文献   

台风Rammasun(2014)与飓风Wilma(2005)快速增强过程的内核结构变化比较     

郑秀丽  吴立广  周星阳  邱文玉  杨华栋  谢彤 《热带气象学报》2020,36(2):219-231

热带气旋的快速增强机制目前仍然不太清楚,不少研究开始关注快速增强过程中热带气旋内核结构的变化。通过比较模拟的西北太平洋超强台风Rammasun (2014)和大西洋5级飓风Wilma (2005)快速增强过程中内核结构的变化特点,理解内核结构在快速增强过程中的变化特点。飓风Wilma是一个典型的快速增强热带气旋,快速增强期间具有弱的环境垂直切变、对称的眼墙、较小的中心倾斜以及比较直立的眼墙。但是,台风Rammasun快速增强发生在较强切变(超过10 m/s)环境下,眼墙对流呈高度不对称,强对流基本固定在台风中心的南侧。整个快速增强期间,Rammasun在垂直方向上维持较大的中心倾斜以及较大的眼墙倾斜。结果表明,快速增强也可能在不完全对称的内核结构和倾斜垂直结构的情况下发生。   相似文献   

Seasonal variation in benthic macroinvertebrate assemblages and water quality in an Afrotropical river catchment,northeastern Tanzania     

《Limnologica》2020

Population growth and economic development have resulted in increased water demands, threatening freshwater resources. In riverine ecosystems, continuous monitoring of the river quality is needed to follow up on their ecological condition in the light of water pollution and habitat degradation. However, in many parts of the world, such monitoring is lacking, and ecological indicators have not been defined. In this study, we assessed seasonal variation in benthic macroinvertebrate assemblages in a tropical river catchment in northeastern Tanzania, which currently experiencing an increase in agricultural activities. We examined the potential of in-stream environmental variables and land-use patterns to predict the river macroinvertebrate assemblages, and also identified indicator taxa linked to specific water quality conditions. Macroinvertebrate abundance, taxon richness and TARISS (Tanzania River Scoring System) score were higher in the dry season most likely due to higher surface runoff from agricultural land and poorer water quality in the wet season. In the wet season macro invertebrates seem to be limited by chlorophyll-a, oxygen and phosphorous while in the dry season, when water flow is lower, nitrogen and turbidity become important. Substrate composition was important in both seasons. Given the fact that different selective filters limit macroinvertebrate assemblages in both seasons, a complete picture of water quality can only be established by monitoring in both seasons. Riparian buffer zones may help to alleviate some of the observed negative effects of agricultural activities on the river system in the wet season while limiting irrigation return flows may increase water quality in the dry season.  相似文献   

浅谈岸线蚀退与保滩促淤     

袁勇 《海岸工程》2009,28(2):34-37

简要介绍了海岸线蚀退对胜利油田的危害，分析了海岸线蚀退的主要原因，提出应进行重点研究的内容，并提供了几种潜堤的结构型式。  相似文献   

2020年西北太平洋和南海台风活动概述          下载免费PDF全文

周冠博  董林  王海平  刘达 《海洋气象学报》2021,41(1):1-10

利用中央气象台台风实时业务定位资料和地面气象观测资料对2020年西北太平洋和南海的台风活动主要特征以及主要影响我国的台风路径、强度及风雨情况进行了统计分析.2020年西北太平洋和南海共有23个台风生成,较多年平均值(27.0个)偏少4.0个;有5个台风登陆我国,较多年平均值(7.0个)偏少2.0个.2020年台风活动的...  相似文献   

昆山城市热岛效应特征及其关键影响因子研究北大核心          下载免费PDF全文

季群  包云轩  汪婷  吴俊梅  陈粲 《气象科学》2023,43(2):155-166

昆山地处长三角超大城市群中,在热岛效应上受到了上海、苏州等大、中城市的显著影响。利用2014—2017年昆山气象站网逐小时观测资料分析昆山城市热岛强度时空分布特征的基础上,结合归一化建筑指数(Normalized Difference Built-up Index,NDBI),揭示了城市功能分区和城市扩张对该市热岛强度的影响,并通过一套用于城市气候研究的系统的场地分类方法—局地气候分区体系(Local Climate Zones,LCZ),探讨了不同城市用地的热岛强度特征。研究发现:昆山市热岛强度总体呈现夜间强、白天弱的特征。季节变化上表现为秋季最强,冬季次之,春季和夏季较弱;昆山市城市热岛强度处于逐年增长的过程,各镇中平均年际热岛强度增长率最高可达0.19℃·a^(-1)。高热岛强度范围由东南向西北延伸,湖陆风效应对昼夜热岛强度的分布及其变化有一定的影响,由于水体的作用,昆山市NDBI与夜间热岛强度的相关性较差,而与白天的热岛强度呈高度正相关。各镇不同的功能分区对热岛效应有显著影响,且当各镇的平均NDBI每增加0.1时,白天平均热岛强度会增加0.16℃;不同LCZ类型的热岛强度具有显著的差异,且地块城市化程度越高,热岛效应越强。密集低层建筑区(LCZ 3)和工业厂房(LCZ 10)的热岛强度与人类活动密切相关;开阔低层建筑区(LCZ 6)与茂密树木区(LCZ A)热岛强度表现出相似的变化特征;森林绿地(LCZ A、LCZ B)对热岛效应有缓解作用;水体(LCZ G)在白天有一定的降温效果,在夜间则会加剧热岛效应。  相似文献