Low-cost volcano surveillance from space: case studies from Etna, Krafla, Cerro Negro, Fogo, Lascar and Erebus

 Satellite data offer a means of supplementing ground-based monitoring during volcanic eruptions, especially at times or locations where ground-based monitoring is difficult. Being directly and freely available several times a day, data from the advanced very high resolution radiometer (AVHRR) offers great potential for near real-time monitoring of all volcanoes across large (3000×3000 km) areas. Herein we describe techniques to detect and locate activity; estimate lava area, thermal flux, effusion rates and cumulative volume; and distinguish types of activity. Application is demonstrated using data for active lavas at Krafla, Etna, Fogo, Cerro Negro and Erebus; a pyroclastic flow at Lascar; and open vent systems at Etna and Stromboli. Automated near real-time analysis of AVHRR data could be achieved at existing, or cheap to install, receiving stations, offering a supplement to conventional monitoring methods. Received: 21 January 1997 / Accepted: 3 April 1997     

Vicissitude of Sogo Nur and environmental-climatic change during last 1500 years

Lakes in arid zone are sensitive to climatic changes. The lacustrine sediment sequence in Sogo Nur has well and truly recorded climatic events such as the Sui-Tang Dynasty Warm Period, the Song-Liao Dynasty Cold Period, the Medieval Warm Period, the Little Ice Age and the 20th Century Warm Period. Commonly, the climate in warm Periods was relatively humid,accordingly the lake area extended and water level rose, and vice versa. Apart from climatic change, human activity is also an important factor of influencing lake vicissitude, and they played the dominant role alternatively during different periods; the factor of climatic change predominated in historical period, while since the beginning of the 20th century the utilization of water resources by human has became decisive.     

沉积物记录的亚高山湖泊环境变化——以鄂东南云中湖为例

根据云中湖27 cm长沉积岩芯进行元素、粒度和硅藻多指标分析以及²¹⁰Pb测年,结合流域气候和人类活动等历史资料,反演1958年以来云中湖在气候变化和人类活动影响下的环境变化。冗余分析结果显示云中湖沉积硅藻组合变化与Al、Fe、Pb和温度四个变量显著相关。硅藻属种聚类分析的结果表明云中湖环境变化经历了两个阶段：1958-1993年间喜碱性水体的Achnanthes minutissima和Fragilaria nanana属种大量出现与较高CIA指数响应于气候调控下的流域侵蚀过程;1993年以来气候变暖与旅游发展引起入湖营养盐增加是Cyclotella pseudostelligera和Aulacoseira alpigena等中—富营养硅藻种增殖的主要诱因。重建亚高山湖泊在气候变化以及人类活动影响下湖泊生态系统的演化,为保护亚高山湖泊生态环境和改善流域水质提供参考。     

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洱海近区非潮汐重力变化的研究

本文给出了洱海水体变化对局部重力场影响的解析式和量级,并且将理论结果与实测的水文、流动重力及定点重力分析结果作了比较,结果表明:影响的程度因距洱海的距离而异。在台站重力测量中,由水体变化产生的干扰淹没在零漂之中(约占每日零漂量的2％),潮汐主频段上没有明显的干扰信号;而对流动重力测量,在水体变化大的情况下,部分测点所产生的变化可以达到10×10~(-8)m/s~2。     

定边盐湖地质特征及其形成条件

定边盐湖区共有14个硫酸盐型盐湖。固体盐矿主要产于苟池和花马池,上部为石盐层,下部为芒硝和白钠镁矾层,其~(14)C年龄距今14700～12400a间。液体矿分布广,包括湖表卤水、晶间卤水和孔隙卤水,其蒸发析盐过程服从Na~+·Mg~(2+)∥Cl~-·SO_4~(2-)—H_2O四元体系相图所指示的规律。湖盆多彼此孤立不相连,为河流侵蚀和风蚀成因。盐分主要来源于白垩纪地层和周边盐渍地。     

人类活动和气候变化对艾比湖湖泊面积的影响

新疆艾比湖地处我国西北干旱区,为典型的内陆封闭性湖泊,由于受内陆极端干旱气候及人类活动的影响,导致湖泊面积显著变化。湖泊面积变化所导致的生态环境恶化已成为制约当地社会经济发展的重要因素。以不同年份的多源遥感数据为数据源,分析了1972-2008年湖泊面积变化情况,并分析了特征年内湖泊面积变化的原因。认为气候要素中降水对湖泊面积影响较大,另外,人类活动引起绿洲变化,而绿洲农业灌溉用水对湖泊面积变化影响较大。同时,还分析了湖泊萎缩引起的湖泊水质恶化以及湖滨植被退化和区域沙漠化等环境效应,结果表明,湖泊面积是流域生态保障的重要指标,可作为反应湖泊流域生态情况的重要指标。由此提出了保护艾比湖生态环境的若干建议。