Quantification of contemporary storm-induced boulder transport on an intertidal shore platform using radio frequency identification technology

Extreme storm events are known to produce, entrain, transport and deposit sizable boulders along rocky coastlines. However, the extent to which these processes occur under moderate, fetch-limited wave conditions is seldom considered. In this study we quantify boulder transport at a relatively sheltered location subject to high-frequency, low-magnitude storm activity. This was achieved by deploying radio frequency identification (RFID) tags within 104 intertidal limestone boulders ranging in size from fine to very coarse (intermediate axis: 0.27–2.85 m). The study was conducted over 3 years (July 2015–July 2018) and encompassed numerous storm events. Tagged boulders were relocated during 17 field surveys and their positions recorded using a differential global positioning navigation satellite system (DGNSS). On completion, we identified boulder displacement in 69% of the tagged array. The accrued boulder transport distance amounted to 233.0 m from 195 incidents of displacement, including the movement of a boulder weighing an estimated 11.9 t. Transport was not confined to autumn and winter storms alone, as displacement was also recorded during summer months (April–September), despite the seasonally reduced wave magnitude. Boulder production by wave quarrying was documented in three tagged clasts, confirming observations that the shore platform is actively eroding. Incidents of overturning during transport were also recorded, including multiple overturning of clasts weighing up to 5 t. We further identify a statistically significant difference (maximum p-value ≤ 0.03) between the transport distances attributed to constrained and unconstrained boulders, suggesting that the pre-transport morphological setting exerts considerable control over boulder transport potential. The findings establish low to moderate storm waves as a key component in the evolution of the study site. More broadly, we claim that high-frequency, low-magnitude storms regularly modify these overlooked rocky coastal locations, suggesting that the hydrodynamic capability at such sites may previously have been underestimated. © 2020 John Wiley & Sons, Ltd.     

气候变化背景下淮河流域场次暴雨事件时空演变分析

全球气候变化对暴雨洪涝等极端天气事件的发生产生了显著影响,识别气候变化背景下暴雨事件的时空变化特征是暴雨洪涝灾害综合应对的关键.以淮河流域为研究区,基于流域内229个气象站点1950-2012年的实测逐小时降水数据,遵循淮河流域实际情况对暴雨事件进行场次划分,并以此作为基础统计单元,借助地理信息系统平台,运用统计学方法并结合气象学理论,以场次暴雨事件开始时间、达到雨强峰值历时、场次平均暴雨历时及暴雨事件发生频次4个指标分析不同年代背景下淮河流域场次暴雨事件发生的过程变化及时空演变特征.结果表明：在气候变化的背景下,场次暴雨发生时间呈现宽幅化和极值化的变化趋势,暴雨发生时间出现了后移和双峰化的特征;暴雨历时及到达雨强峰值历时均呈现增加趋势,整个流域场次暴雨事件在1990s-2000s进入一个增加时期;全球性的气候变化使流域内暴雨事件发生的频次不断增加,历时不断增大,长历时高频次特征明显,尤其是近20 a来,淮河流域暴雨事件高发区域呈现出从流域部分地区向全流域扩张的趋势.     

河西走廊东部低温事件变化特征

根据1960-2015年河西走廊东部5个气象站逐日最低、平均气温资料,通过固定阈值和百分位阈值法定义了低温事件,采用气候统计学方法,分析了该区域低温事件的强度、极值和日数的变化特征,统计结果显示,受海拔高度、地形地势和植被覆盖的影响,河西走廊东部低温事件的空间分布均存在明显地域差异,均为高寒山区天祝强度和极值最强,日数最多,绿洲平原区凉州强度和极值最弱,日数最少。河西走廊东部年代和年低温事件强度和极值呈减弱趋势,日数呈减少趋势,2010-2015年减弱和减少的趋势尤为明显。年低温事件强度、极值和日数的时间序列均存在着周期性变化,但都没有发生气候突变,只出现了转折年份。两种标准的低温事件均出现在1~3月和11~12月,强度、极值和日数高峰值均在1月或12月。年低温事件存在一定的异常性,正常低温事件强度、极值和日数的年份概率在64.3%～80.4%,对安全生产造成危害的低温事件强度、极值偏强和特强年份的概率在7.1%～16.1%,日数偏多和特多年份的概率共为16.1%。本研究可为低温的预报预警提供技术支持,同时可为地方政府提供准确的决策依据,对区域气候变化研究和经济发展有重要意义。     

Major sporting events and geographies of disability

Major sporting events for athletes with disabilities have become part of a strategic agenda to create positive social legacies for those typically marginalized in their communities. These events are subject to strict guidelines set forth by the International Paralympic Committee to deliver broad-based accessibility. In some cases, changes to accessibility are temporary, wherein other upgrades remain as permanent fixtures for venues, transportation, and public spaces. However, the temporality at the heart of major event projects can also work against long-term, sustainable improvements to the material conditions persons with disabilities face as they experience the urban realm. In this paper, we draw upon case studies of the Glasgow 2014 Commonwealth Games and the Toronto 2015 Parapan American Games to explore the value of major sporting events in delivering urban accessibility improvements and offer a critical commentary on the limitations of the event project to herald sustainable change.     

西北干旱区极端气候水文事件特征分析

中国西北干旱区是对全球变化响应最敏感地区之一。气候变化导致气候水文系统的不稳定性加剧,极端气候水文事件的频度和强度增大、重现期缩短,灾害程度加重。借助资料分析和文献阅读,对过去50 a中国西北干旱区极端气候/水文事件的发生规律、影响机制及未来趋势进行了梳理总结,主要结论如下：（1）西北干旱区的极端气候/水文事件呈逐年增加趋势,特别是20世纪70年代以来增加显著;气温和降水极值都表现为一致的增强趋势。降水量的增多是降雨频率和强度共同增加的结果。（2）中国西北干旱区低温、降水极值在1986年左右发生了明显的突变,高温极值在1996年左右发生突变。突变后,气温和降水极值均发生了显著增强变化。（3）北半球极涡面积指数和青藏高原指数对西北干旱区气候极值变化具有重要影响,冬季极值还受冬季北极涛动和北大西洋涛动等影响。（4）新疆地区有变暖湿趋势,而河西走廊东部则为变干趋势。强大的西伯利亚高压和增强的贝加尔湖气流造成新疆地区降水增加,而河西走廊干旱增加是由东亚夏季风减弱引起的。     

太湖东岸平原中全新世气候转型事件与新石器文化中断

来自苏州草鞋山遗址年代学,生物地层学和沉积学的分析结果表明,本区新石器文化演进与全新世气候突变的事件有关。高分辨率,连续的孢粉,粒度和磁化率记录证实,崧泽文化是在暖湿气候条件下出现和繁荣的,发生在５３６５ａＢ．Ｐ左右的一次干旱事件使之走向衰落,而出现在全新世大西洋期与亚北方期过渡阶段的一次气候转型事件中断本区文明达２００年之入。５１６０ａＢ．Ｐ．以后,气候转为暖干,经历了一次干旱事件后,良渚文化发     

Empirical models of rain-spells characteristics – A case study of a Mediterranean-arid climatic transect

Environmental (geomorphological, hydrological and ecological) processes are controlled by rainfall, particularly in the Mediterranean, semi-arid and arid regions. Rainfall was analyzed using the concept of rain-spells, i.e., a period of successive rain days preceded and followed by at least one day without rainfall. Daily data from 13 stations along a climatic transect extending from the Judean Mountains with a Mediterranean climate to the Dead Sea arid region in Israel were studied. Rain-spell characteristics (number, yield and duration), based on these data, are presented for different rainfall thresholds, which might be used for different environmental processes such as rock weathering, soil organic matter dynamics, landslides, overland flow and floods and soil erosion. Three estimation models have been developed in order to predict the mean annual Number of Rain-Spells (NRS), mean Rain-Spell Yield (RSY), and mean Rain-Spell Duration (RSD) for the mean annual rainfall and for any given rainfall threshold. These models can be used for current climatic conditions and for scenarios in which the rainfall total changes.     

国内外高山林线研究综述

高山林线作为山地郁闭林和高山草甸的分界在山地生态系统中占有重要地位。以往对山地生态的研究远少于对其它类型陆地生态系统的研究,高山林线方面的研究就更为缺乏。讨论了高山林线的概念和内容,对国内外高山林线研究及特点作了简单回顾,指出高山林线的研究意义及在我国开展此项研究的初步方案。     

未来气候变化情景下横断山北部灾害易发区极端降水时空特征

极端降水是导致气候变化下滑坡、泥石流等山地灾害变化的重要因素。极端降水的时空特征作为气候变化下山地灾害风险的研究热点之一,为滑坡等山地灾害危险性评价和构建山地社会安全空间奠定了重要基础。尤其对于地形复杂、灾害频发的横断山地区,高精度的极端降水时空特征研究有利于优化国土空间,促进当地减轻灾害风险与加强气候变化适应相结合。本研究以横断山北部岷山、邛崃山和大雪山为例,充分考虑区域复杂地形的影响,在全球气候模式降水数据的基础上,采用统计降尺度的方法,获取该区域2010—2060时段的逐日降水数据(空间分辨率1×1km);并充分考虑极端降水可能对物理事件造成的影响,构建包括绝对量指数、频度指数和强度指数的极端降水评价指标体系。研究结果表明,未来气候变化下,研究区极端降水总体呈现增加—减少—增加的趋势,短时极端降水和持续性极端降水的空间分布相对一致。就短时极端降水而言,大部分区域发生50mm以上极端降水事件的次数较多,而研究区中部邛崃山区甚至会发生超过100mm的极端降水事件。持续性事件的分布受地形阻隔作用影响,主要发生在大雪山高山区域和邛崃山区。结合研究区地理环境条件,地质灾害风险在未来气候变化情景下可能增加。     

Evaluating climate model outputs for hydrological applications

Citation Wilby, R. L. (2010) Evaluating climate model outputs for hydrological applications – Opinion. Hydrol. Sci. J. 55(7), 1090–1093.