Investigating the mechanisms leading to the deglaciation of past continental northern hemisphere ice sheets with the CLIMBER–GREMLINS coupled model

A coupling procedure between a climate model of intermediate complexity (CLIMBER-2.3) and a 3-dimensional thermo-mechanical ice-sheet model (GREMLINS) has been elaborated. The resulting coupled model describes the evolution of atmosphere, ocean, biosphere, cryosphere and their mutual interactions. It is used to perform several simulations of the Last Deglaciation period to identify the physical mechanisms at the origin of the deglaciation process. Our baseline experiment, forced by insolation and atmospheric CO₂, produces almost complete deglaciation of past northern hemisphere continental ice sheets, although ice remains over the Cordilleran region at the end of the simulation and also in Alaska and Eastern Siberia. Results clearly demonstrate that, in this study, the melting of the North American ice sheet is critically dependent on the deglaciation of Fennoscandia through processes involving switches of the thermohaline circulation from a glacial mode to a modern one and associated warming of the northern hemisphere. A set of sensitivity experiments has been carried out to test the relative importance of both forcing factors and internal processes in the deglaciation mechanism. It appears that the deglaciation is primarily driven by insolation. However, the atmospheric CO₂ modulates the timing of the melting of the Fennoscandian ice sheet, and results relative to Laurentide illustrate the existence of threshold CO₂ values, that can be translated in terms of critical temperature, below which the deglaciation is impeded. Finally, we show that the beginning of the deglaciation process of the Laurentide ice sheet may be influenced by the time at which the shift of the thermohaline circulation from one mode to the other occurs.     

旅游生态环境容量的经济学探讨

在总结旅游环境容量研究进展的基础上，提出了研究旅游环境容量意义及其概念体系，并就影响旅游环境容量的关键性因子－旅游生态环境容量进行了分析，运用经济学的理论和方法，提出了引起旅游生态环境容量的深层原因是外部不经济性，最后就为了实现资源环境的可持续发展，应该从法律、行政，经济、社会等角度对社会各利益加以协调，构建了有效的制度平台和相应的措施，使外部成本内部化，并提出了解决这些问题的具体对策和建议。     

THE EFFECTS OF EXTERNAL FORCING,DISSIPATION AND NONLINEARITY ON THE SOLUTIONS OF ATMOSPHERIC EQUATIONS*

Based on the primitive equations of the atmosphere,we study the effects of external forcing.dissipation and nonlinearity on the solutions of stationary motion and non-stationary motion.The results show that the asymptotic behavior of solutions of the forced dissipative nonlinear system is essentially different from that of the adiabatic non-dissipative system,the adiabatic dissipative system,the diabatic non-dissipative system and the diabatic dissipative linear system,and that the joint action of external forcing,dissipation and nonlinearity is the source of multiple equilibria.From this we can conclude that the important actions of diabatic heating and dissipation must be considered in the models of the long-term weather and the climate.     

台风区和外围暴雨区的旋转风、散度风动能收支

用完全的散度风(v_D)和旋转风(v_R)动能收支方程对8116台风和8407台风以及8116台风与其外围暴雨区的关系作了讨论。结果表明:台风区的有效位能通过散度风动能(K_D)转换为旋转风动能(K_R).台风向区域外部输出动能,在暴雨区上空通过涡度、散度场相互作用的转换机制由K_R向K_D转换,散度风加大触发对流发展产生暴雨,这可能是台风与其外围暴雨联系的一种能量过程。     

Estimating Climate-Change Impacts on Colorado Plateau Snowpack Using Downscaling Methods

This study develops observed climate-based downscaling transfer functions that are used with general circulation model (GCM) output to assess potential global-change impacts on Upper Colorado Plateau, USA, water resources. Daily automated snow water equivalent stations are used with 700 mb atmospheric circulation to determine empirical transfer functions. Downscaling methodologies using multiple regression and neural networks are evaluated, with the neural network results explaining approximately 70%of the daily snowfall variance. The neural network-based transfer functions are used with the GENESIS GCM to simulate snowfall characteristics in both a 1xCO₂ and a 2xCO₂ climate. While the total precipitation simulated by the 2xCO₂ analysis remains nearly the same as today, less will fall as snow; specifically, snow water equivalence shows significant reduction (except in the Green River Basin) as the snow season is reduced by 58 days on average.     

高山区雪堆储雪的实验和模拟计算

随着全球气候变暖,滑雪运动呈现出对气候变化高度的敏感性和依赖性,各地滑雪季将不同程度地缩短。储雪作为一种应对气候变化的方法在雪务保障中逐渐得到研究和应用。在新疆阿勒泰地区吉木乃县开展储雪实验,应用谐波反应法研究了雪堆融化量与外界空气温度、太阳辐射和绝热保温结构热学性能之间的定量关系。实验中,覆盖两层绝热保温材料雪堆1的平均融化量为18.0 kg·d^-1（相当于初始质量的0.85%）,未覆盖绝热保温材料雪堆2的平均融化量为120.8 kg·d^-1（相当于初始质量的6.67%）。模拟期间观测到的雪堆1质量减少了1 438.0 kg,对应的模拟值为1 520.8 kg。谐波反应法可以为评价绝热保温结构的热学性能和提前确定储雪量提供重要的参考依据。由于许多物理过程都未考虑,导致模拟的雪堆融化量与实际融化量之间存在不确定性。雪堆所用绝热保温结构的性能可以用反射率、总传热系数、衰减度和延迟时间来衡量。     

基于外部性理论的湿地退化成因分析及对策研究

基于生态经济学中的外部性原理,结合湿地生态系统的准公共物品属性、外部经济性、外部不经济性以及代际外部性等属性,分析湿地退化的成因.结果表明：湿地萎缩加剧、生态服务功能衰退主要是由于人类缺乏对湿地功能与效益的正确认识,以及不合理的利益分配机制导致的成本外溢现象,从事湿地保护的正外部性行为未得到应有的补偿,负外部性行为未付出应有的代价,并提出应建立因地制宜的多元化生态补偿机制.     

动机、成本、风险：家长视角下研学旅游产品价值感知研究

以中小学生自然教育研学旅游作为具体情境,基于539份家长问卷数据阐释研学旅游动机与价值感知之间的关系,并通过成本感知和风险感知探讨其内在机制和边界条件。结果表明,家长感知的研学旅游动机越强烈,越容易感知到研学旅游产品所传递的价值,验证了研学旅游情境下动机对价值感知的积极影响,也形成了对动机与价值之间关系研究的理论补充。并且,这一动机除了直接作用于价值感知外,还会通过成本感知的部分中介作用影响价值感知,揭示了中国家长对于教育价值的重视会削弱其对“利失”的感知。此外,进一步验证了风险感知的积极影响,即家长感知研学旅游的不确定性水平越高,动机对价值感知的积极影响越明显,且会抑制成本感知对价值感知的负向作用,但风险感知水平达到一定高度时,其对成本感知与价值感知间的抑制作用将不显著。因此,面向需求设计打造产品,突出产品价值、加大宣传营销力度、把控活动安全、合理制定价格,获取家长群体的认同接受,将是研学旅游进一步拓展市场的重要考量。     

基于引文分析法的“点-轴系统”理论研究述评

论文采用引文分析法,对陆大道院士所著《关于“点-轴”空间结构系统的形成机理分析》一文的349篇引文进行分析,从引文数量、引文作者、发文期刊、研究案例地、学科领域、研究主题、引用动机7个方面,探究“点-轴系统”理论的研究现状。结果表明：自2002年以来,“点-轴系统”理论的引文数量整体呈上升趋势,研究主题聚焦于区域经济和旅游发展;研究案例地以省级和市级中观尺度为主,多为单一型研究区,主要集中在西北丝绸之路经济带、东北辽宁经济圈、西南藏滇川渝、东部长三角四大热点区域;引文质量普遍较高,并且具有多学科交叉应用的特点,但批判性思考和创造性提升相对较少。基于此,论文从拓展研究和实践应用2个角度对“点-轴系统”理论未来发展进行了展望,以期为相关研究提供参考。     

京津冀城市群虚拟水贸易的近远程分析

虚拟水贸易能重新分配区域间的水资源。在京津冀协同发展的背景下,厘清京津冀城市群与外部的虚拟水贸易及城市群内部的虚拟水流动,有助于深入理解该地区的水资源供需现状及问题,为制定虚拟水贸易相关策略、实现区域水资源优化配置、保障区域水资源安全提供决策支持。本文基于2010年全国区域间投入产出表,测算了京津冀城市群各省（市）水足迹及与全国各省域单元的虚拟水贸易量。从近远程视角定量评估城市群地区对内、外部水资源的依赖程度,并分析虚拟水贸易的距离特征。研究发现：① 京津冀城市群各省（市）各部门用水系数显现出差异性,农业部门用水强度最高,直接用水与完全用水系数分别超过300 m ³/万元和400 m ³/万元;② 京津冀城市群内部各省（市）人均消费水足迹差异大,北京、天津、河北的人均水足迹分别为405 m ³、565 m ³、191 m ³;③ 京津冀城市群的消费水足迹遍布全国各省域单元,近程水足迹与远程水足迹分别为91.4亿m ³、198.5亿m ³,其中,近程水足迹主要来源于本省（市）,西部地区对远程水足迹的贡献最大;④ 京津冀城市群的虚拟水输入总体偏向来源于距离较近的省域单元,北京、天津、河北水足迹距离来源地的平均距离分别为1049 km、1297 km、688 km;⑤ 北京和天津为虚拟水贸易的净流入区,对外部水资源的依赖性强;河北为虚拟水贸易的净流出区,为京津冀城市群及其他地区供给水资源,虚拟水净流出进一步加剧了河北的水资源短缺。未来,受人口增长、经济发展等因素影响,京津冀城市群的水资源压力将进一步加剧,提高用水效率、升级产业结构、提倡低水足迹消费模式、实行虚拟水战略是实现京津冀城市群可持续发展的有效途径。