Validating the dynamic downscaling ability of WRF for East Asian summer climate

This work aims, as a first step, to analyze rainfall variability in Northern Algeria, in particular extreme events, during the period from 1940 to 2010. Analysis of annual rainfall shows that stations in the northwest record a significant decrease in rainfall since the 1970s. Frequencies of rainy days for each percentile (5th, 10th, 25th, 50th, 75th, 90th, 95th, and 99th) and each rainfall interval class (1–5, 5–10, 10–20, 20–50, and ≥50 mm) do not show a significant change in the evolution of daily rainfall. The Tenes station is the only one to show a significant decrease in the frequency of rainy days up to the 75th percentile and for the 10–20-mm interval class. There is no significant change in the temporal evolution of extreme events in the 90th, 95th, and 99th percentiles. The relationships between rainfall variability and general atmospheric circulation indices for interannual and extreme event variability are moderately influenced by the El Niño-Southern Oscillation and Mediterranean Oscillation. Significant correlations are observed between the Southern Oscillation Index and annual rainfall in the northwestern part of the study area, which is likely linked with the decrease in rainfall in this region. Seasonal rainfall in Northern Algeria is affected by the Mediterranean Oscillation and North Atlantic Oscillation in the west. The ENSEMBLES regional climate models (RCMs) are assessed using the bias method to test their ability to reproduce rainfall variability at different time scales. The Centre National de Recherches Météorologiques (CNRM), Czech Hydrometeorological Institute (CHMI), Eidgenössische Technische Hochschule Zürich (ETHZ), and Forschungszentrum Geesthacht (GKSS) models yield the least biased results.     

生态建设背景下三江源自然保护区生态系统服务价值变化

青海三江源是我国淡水资源的重要补给地,也是全国生态保护和建设工程的重点实施区域,对其开展生态恢复过程的生态系统服务价值变化研究,有利于揭示生态保护和建设工程的实施效果。在构建三江源生态系统服务价值评估指标体系的基础上,选择生态工程前后两个时间段(2000年和2008年),采用物质量和价值量相结合的方法对三江源自然保护区生态系统服务价值进行了评估和对比分析,结果表明:2000—2008年保护区生态系统服务总价值呈现明显的增长趋势,8 a间一共增加1.68×1010元。保护区草地生态系统的整体质量状况大幅度提升,生态系统服务价值增加48.69%,是由生态建设和气候因子变化共同作用的结果;森林生态系统服务价值增加12.71%,主要跟森林区域水热条件的改善有关;水体与湿地生态系统服务价值在8 a间减少56.08%,关键是由区域气温升高和降水量减少所致,而非人为因素的影响;2000—2008年间,保护区人口数量增加了26.08%,较高的人口增长压力促使大量的草地被开垦为农田,导致农田面积增加392.52%,从而引起农田生态系统服务价值大幅波动。     

Responses of vegetation distribution to climate change in China

Climate plays a crucial role in controlling vegetation distribution and climate change may therefore cause extended changes. A coupled biogeography and biogeochemistry model called BIOME4 was modified by redefining the bioclimatic limits of key plant function types on the basis of the regional vegetation–climate relationships in China. Compared to existing natural vegetation distribution, BIOME4 is proven more reliable in simulating the overall vegetation distribution in China. Possible changes in vegetation distribution were simulated under climate change scenarios by using the improved model. Simulation results suggest that regional climate change would result in dramatic changes in vegetation distribution. Climate change may increase the areas covered by tropical forests, warm-temperate forests, savannahs/dry woodlands and grasslands/dry shrublands, but decrease the areas occupied by temperate forests, boreal forests, deserts, dry tundra and tundra across China. Most vegetation in east China, specifically the boreal forests and the tropical forests, may shift their boundaries northwards. The tundra and dry tundra on the Tibetan Plateau may be progressively confined to higher elevation.     

南海神狐海域水合物一维速度结构研究： 基于中—低饱和度水合物区的约束

高精度OBS探测作为目前研究水合物的常用技术手段,可以获取水合物矿体精细速度结构,在研究天然气水合物饱和度、水合物资源的预测与开发等方面具有重要指导意义。然而正演模拟OBS速度结构是繁琐漫长的过程,构建合理的初始模型是后续精细结构快速成像的重要前提。本研究基于全球18个已探明地震波速度的水合物区,分析了水合物矿体内纵波速度的共性特征和影响因素,拟合了水合物矿体带纵波速度与海水深度、沉积物厚度的经验公式。综合经验公式、OBS数据与多道地震剖面,建立了神狐水合物区横向均匀初始模型,并通过射线追踪与走时拟合模拟了神狐海域的一维纵波速度结构。结果表明,神狐水合物矿体带具有高纵波速度(1.83~1.92 km/s）,游离气层具有低P波速度（1.60~1.70 km/s）,此外,基于全球的水合物速度经验公式对神狐海域速度结构模拟具有重要参考意义,有望为获取神狐海域二维/三维精确速度结构提供可靠的初始模型,进而指导水合物精细勘察与资源评估。     

Attribution analyses of potential evapotranspiration changes in China since the 1960s

This paper focuses on the primary causes of changes in potential evapotranspiration (ET_o) in order to comprehensively understand climate change and its impact on hydrological cycle. Based on modified Penman-Monteith model, ET_o is simulated, and its changes are attributed by analyzing the sensitivity of ET_o to influence meteorological variables together with their changes for 595 meteorological stations across China during the period 1961–2008. Results show the decreasing trends of ET_o in the whole country and in most climate regions except the cold temperate humid region in Northeast China. For China as a whole, the decreasing trend of ET_o is primarily attributed to wind speed due to its significant decreasing trend and high sensitivity. Relative humidity is the highest sensitive variable; however, it has negligible effect on ET_o for its insignificant trend. The positive contribution of temperature rising to ET_o is offset by the effect of wind speed and sunshine duration. In addition, primary causes to ET_o changes are varied for differing climate regions. ET_o changes are attributed to decreased wind speed in most climate regions mainly distributed in West China and North China, to declined sunshine duration in subtropical and tropical humid regions in South China, and to increased maximum temperature in the cold temperate humid region.     

Spatial Variations of b-Values in the Coastal Area of Guangdong

We used earthquake catalogs recorded by Guangdong Seismological Network from 2008 to 2014 to resolve the spatial variations of b-values in the coastal area of Guangdong, particularly in three key research areas(Yangjiang, Heyuan, and offshore Nanao Island) with strong seismicity. Our results revealed that b-values exhibited significant spatial variations, and zones with low b-values could indicate the most likely seismogenic area of large earthquakes. We observed three clear low b-value patches in the offshore Nanao Island. We found a distinct high b-value peak at the depth of 11 km and two minimum peaks at about 14 and 7–8 km in the Yangjiang area. The overall b-values generally decrease with depth in the Heyuan area. The spatial variations of b-values reflect tectonic anomalies; that is, the ‘low-high-low' distribution of b-values in the offshore Nanao Island and the Yangjiang area may indicate the anomaly of the crustal structure with a weak layer. The b-values of reservoir-induced seismicity are obviously lower than that induced by tectonism. This finding indicates that the reservoir area is generally at high stress state under the condition of high pore pressure. We inferred that large earthquakes might be prone to occur at 10–12 km depth in the offshore Nanao Island, at 12–15 km depth in the Yangjiang area, and at the lower part of the seismic activity zone in the Heyuan area. Moreover, the upstream area of the Xinfengjiang reservoir is the most likely area of future large earthquakes in the Heyuan area.     

自然地理学创新发展与展望

自然地理学自中国科学院地理科学与资源研究所建立以来一直是立所的核心学科,长期以服务国家重大需求为使命,在综合自然地理、气候、地貌、水文、土壤地理、生物地理、化学地理等各学科领域取得一批重要科技成果和进展,奠定了自然地理各分支学科在国内外的优势,为国家科技创新、区域经济社会可持续发展做出了重要贡献。本文回顾了中国科学院地理科学与资源研究所自然地理学的创新发展历程,总结了自然地理学取得的学术成就与标志性进展,并展望了中国科学院地理科学与资源研究所自然地理学未来发展,提出以陆地表层要素—过程交互作用机制,陆地表层格局动态研究,陆地表层系统过程的综合集成与模拟,陆地表层系统有序人类活动的可持续范式和调控机制为核心的发展战略。     

区域植被覆盖的多尺度空间变异性——以贵州喀斯特高原为例

地理格局尺度依赖性的客观存在,要求在连续尺度序列上对区域植被覆盖空间变异性进行考察,以真实反映植被覆盖空间特征。以贵州喀斯特高原为例,借助地统计学和GIS 软件,揭示了研究区NDVI的空间变异特征,并进行了空间变异与空间尺度的耦合研究。结论如下：① NDVI空间变异程度表现出明显的尺度依存性,空间尺度的粗粒化对NDVI的平滑作用非常显著,但两种重采样方法对原始数据的粗粒化作用机制不同;② 基于不同遥感数据源获得的NDVI数据之间空间格局差异明显,而且传统统计结果与地统计学结果明显不同,说明空间信息对数据间的差异性统计影响显著;③ NDVI空间变异性呈现显著的各向异性,并表现出对遥感数据源的敏感性。     

气候变化情景下中国自然生态系统脆弱性研究

本研究以动态植被模型LPJ 为主要工具,以区域气候模式工具PRECIS 产生的A2、B2和A1B情景气候数据为输入,模拟了未来气候变化下中国自然生态系统的变化状况,应用脆弱性评价模型,评估中国自然生态系统响应未来气候变化的脆弱性。结果表明:未来气候变化情景下中国东部地区脆弱程度呈上升趋势,西部地区呈下降趋势,但总体上,中国自然生态系统的脆弱性格局没有大的变化,仍呈现西高东低、北高南低的特点。受气候变化影响严重的地区是东北和华北地区,而青藏高原区南部和西北干旱区受气候变化影响,脆弱程度明显减轻。气候变化情景下的近期气候变化对我国生态系统的影响不大,但中、远期气候变化对生态系统的负面影响较大,特别是在自然条件相对较好的东部地区,脆弱区面积增加较多。     

极端事件对人类系统的影响

在IPCC特别报告《管理极端事件和灾害风险,推进气候变化适应》中,极端天气气候事件对人类系统的影响是最重要的影响评估内容之一,其评估结果为：极端影响可能缘于极端天气气候事件,但也可能并非极端事件的后果。暴露度和脆弱性是灾害风险的重要决定因素;极端和非极端天气气候事件的严重程度和影响在很大程度上取决于对这些事件的脆弱性和暴露度水平;人居模式、城市化和社会经济状况的变化已经影响观测到的脆弱性和暴露度的变化趋势;无论在发达国家还是发展中国家,沿海人居环境均暴露于极端事件,并受其影响,如小岛屿国家和亚洲大三角洲地区;脆弱人口还包括难民、国内流离失所的人和那些生活在边远地区的人;极端事件将极大地影响与气候联系密切的部门,如水、农业、食物安全、健康和旅游业。