Stratospheric entry point for upper-tropospheric air within the Asian summer monsoon anticyclone     

QiuJun Fan  JianChun Bian  Laura L. Pan 《中国科学:地球科学(英文版)》2017,60(9):1685-1693

The Asian summer monsoon (ASM) anticyclone isolates upper-tropospheric air within the interior of the anticyclone from the outside. Forward trajectory simulations in previous studies have shown that much of the air within the ASM anticyclone can be trapped for up to two or three weeks, not only laterally but also vertically. Here, we investigate the locations of exit points for upper-tropospheric air trapped within the ASM anticyclone, especially the preferred tropopause-crossing locations, using a 3-dimensional trajectory model. Forward trajectory calculations show two-thirds of the air crosses the tropopause at the southern part of the anticyclone via upward diabatic transport. Furthermore, some air crosses at northern and eastern parts via isentropic shedding, but air crosses rarely through the center of the anticyclone. However, calculations also show that many stratospheric parcels within the anticyclone are traceable from the upper-tropospheric anticyclone. This implies they cannot break through the tropopause directly overhead but instead enter the stratosphere via other entry points.  相似文献   

徐霞客对湖南南部岩溶地貌考察研究的述评     

卞鸿翔 《中国岩溶》1991,10(3):239-243

<正> 明代杰出的地理学家徐霞客于公元1637年春季在湖南南部(简称湘南地区)进行了长达115日的考察。湘南地区气候温暖,降雨充沛。这里除南岭,南岳等中山区为花岗岩及变质岩外,广大丘陵低山区古生代碳酸盐岩分布相当广泛,亚热带季风型岩溶地貌在这里发育较为典型。徐霞客在湘南寻访名山幽壑、奇峰异洞,对岩溶地貌的研究成为他这次旅行考察的重要内容。   相似文献   

北极边界层物理过程的考察与研究   总被引：5，自引：3，他引：2       下载免费PDF全文

陆龙骅  卞林根  逯昌贵 《极地研究》2004,16(3):181-192

北极边界层物理过程的考察与研究是北极大气科学研究的重要组成部分。我国的北极边界层实地考察和研究始于上世纪 90年代 ,近 1 0余年来有较大的进展。本文从大气科学角度阐述了北极边界层物理过程考察与研究的意义 ,回顾了国内外北极边界层物理过程考察与研究的历史和现状 ,介绍了近年来我国北极边界层物理过程考察与研究的新进展 ,提出了北极边界层物理过程考察与研究的前沿问题和发展方向。  相似文献   

A Dynamic Network with Individual Mobility for Designing Vaccination Strategies     

Liang Mao  Ling Bian 《Transactions in GIS》2010,14(4):533-545

Vaccination is a primary means to control infectious diseases. Few studies on vaccination strategies have explicitly considered the mobility of individuals. This article aims to evaluate the efficacy of three vaccination strategies in a dynamic social network, in which individuals are mobile between and within communities. The three vaccination strategies are applied to this social network for evaluation, including a travel‐based, a contact‐based, and a random vaccination strategy. Simulation results show that the contact‐based strategy, commonly seen in previous studies, is not always the most effective strategy in dynamic networks. This strategy is preferable for a population with a large number of intercommunity travelers, for instance in urban areas. On the other hand, the travel‐based strategy, although directly accounting for individual mobility, is not necessarily the most effective in dynamic networks either. This strategy is recommended for a population with a small number of intercommunity travelers, such as rural areas. In addition, one advantage of the travel‐based strategy over the other two is its efficacy in confining the spatial extent of affected areas. Results suggest that the intercommunity travel of individuals should be a major consideration for choosing proper vaccination strategies. By adding the spatial context into vaccination strategies, this research provides new insights into community‐based planning for infectious disease control.  相似文献   

大兴安岭中段晚二叠世林西组介形虫化石及环境意义     

郑月娟  张健  张海华  张德军  卞雄飞  陈树旺  苏飞  黄欣  宋绍钧 《吉林大学学报(地球科学版)》2020,50(6):1776-1786

晚二叠世-中三叠世在中亚造山带东段构造演化过程中是承上启下的关键地质时期,所以晚二叠世林西组沉积环境对研究古亚洲洋闭合这一重大问题具有重要意义。大兴安岭地区晚二叠世林西组曾有双壳、叶肢介、植物及孢粉化石记录,但鲜有介形虫化石报道。在大兴安岭中段林西组研究中首次发现介形虫化石,经初步研究,主要分子有Kemeroviana,Volganella,Iniella,Qitaina,Darwinuloides,Palaeocypridopsis,Tomiella,Darwinula和Urumqiella等,暂划为Volganella-Kemeroviana组合,其时代为晚二叠世。与俄罗斯地台晚二叠世介形虫化石群关系较为密切,部分属种曾见于我国新疆准噶尔盆地和塔里木盆地。从介形虫化石组合特征和保存特点来看,其生存环境为淡水湖泊,故认为这一地区的林西组为陆相沉积。  相似文献   

非定常过程对大气边界层的内参数与风廓线的影响(二)          下载免费PDF全文

赵鸣  钟世远  卞新棣 《气象学报》1988,46(2):210-218

本文用大气边界层运动方程的数值积分研究了当边界层顶风向不变但风速变化时对大气边界层的内参数u_*/A(u_*为摩擦速度,A为上界风速)和α角(地面风与上界风向的交角)的影响。设上界处风速随时间指数增加及减少,最后趋于定常。在大气正、斜压时,u_*/A及α角的时间变化均是振幅衰减的振荡,最后趋于定常时相应的值。在时间变化过程中的任一时刻,内参数值与当上界条件取该时刻上界风时的定常解结果有一定的差别,严格说,定常时的内参数值并不能直接用于当上界风非定常时。本文还考虑了上界风速非定常对风廓线的影响。  相似文献   

东明县节约集约利用土地的几点做法   总被引：1，自引：1，他引：0  

宗学成  卞向阳 《山东国土资源》2009,25(11):63-64

在国家土地宏观调控政策趋紧的新形势下，如何破解土地制约瓶颈，缓解项目用地矛盾，确保经济又好又快发展，成为摆在各级政府面前亟待研究解决的一个难题。对此，东明县立足实际，经过反复论证和积极探索，坚持以政策“杠杆”为支点，找准土地政策和项目建设的最佳结合点，合理规划建设用地，确保了全县土地利用的总体平衡，走出了一条符合东明特点的科学合理利用土地之路。  相似文献   

Stochastic mechanics-based Bayesian method calibrating the constitutive parameters of the unified model for clay and sand with CPTU data     

Fu  Yanbin  Ma  Chengtao  Bian  Yuewei  Lv  Guiyang  Hu  Yu  Wang  Changhong 《Acta Geotechnica》2022,17(10):4577-4598

  相似文献   

临沂市城区岩溶地下水流模拟          下载免费PDF全文

郭士昌  姚春梅  张乐进  李景波  卞加升 《山东国土资源》2009,25(4)

地下水动力条件变化是导致临沂市城区岩溶塌陷的诱因和动因，通过分析岩溶区地质及水文地质条件，建立了临沂市城区岩溶地下水流数值模型，预测了2007年6月至2019年6月地下水水位时空变化过程。从流场拟合情况看，所建模型拟合效果良好，客观反映了地下水系统演化规律，可以用于岩溶塌陷预警预报，为岩溶塌陷地质灾害防治提供技术依据。  相似文献   

The Cretaceous volcanic succession around the Songliao Basin,NE China: relationship between volcanism and sedimentation     

Pujun Wang  Yanguang Ren  Xuanlong Shan  Shaobo Sun  Chuanbiao Wan  Weihua Bian 《Geological Journal》2002,37(2):97-115

With volume ratio of 8:1:1.5 amongst acidic, intermediate and basaltic rocks, the Cretaceous volcanics around the Songliao Basin are a series of high‐K or medium‐K, peraluminous or metaluminous, calc‐alkaline rocks, lacking typical basalts and peralkaline members of typical rift‐related types. Their eruption ages range between 133 and 127 Ma, 124 and 122 Ma and 117 and 113 Ma respectively. They are high in total (Rare earth element) REE contents (96.1–326 ppm), enriched in LREE and depleted in HREE (LREE/HREE = 4.6–13.8), with negative Eu and Ce anomalies (Eu/Eu* = 0.04–0.88; Ce/Ce* = 0.60–0.97). They have enriched large‐ion lithophile elements (e.g. K, Ba, Th) and depleted high field strength elements (e.g. Nb, Ti and Y), suggesting a subduction‐related tectonic setting. The volcanic activities migrated from south to north, forming a successively northward‐stepping volcanic series and showing a feature significantly different from the overlying sedimentary sequence striking northeast. Thus, an overlap basin model was proposed. Accompanied by opening of the basin, the volcanogenic succession was formed at the block‐faulting stage (131–113 Ma) owing to the closure of the Mongolia–Okhotsk ocean in the Jurassic and early Cretaceous, while the overlying sedimentary sequence was unconformably deposited at the spreading stage (Albian–Maastrichtian) owing to the oblique subduction of the Pacific plate under the Eurasian plate. The volcanic succession constitutes the lower unit of basin filling and is the forerunner of further basin spreading. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献