利用船测数据以及Landsat-7 ETM+影像评估南极海冰区AMSR-E海冰密集度

利用第26次中国南极科学考察期间收集的海冰密集度船基观测资料以及由Landsat-7ETM+得到的海冰密集度来验证AMSR-E南极海冰区海冰密集度产品的精度。AMSR-E海冰密集度与船基目视观测的海冰密集度存在着一定的线性关系（R2=0.816）,但两者匹配得并不是很好。与ETM+海冰密集度相比,AMSR-E数据趋向于低估海冰密集度,在25景晴空条件下的ETM+影像中,平均海冰密集度偏差（AMSR-E海冰密集度-ETM+海冰密集度）从-5.33%到-21.5%,而相应的均方根误差RMSE（RootMeanSquaredErrors）从13.7%到33.8%。依据Landsat-7ETM+海冰分类,AMSR-E数据海冰密集度最大的误差产生于新冰区。     

山地冰川流动模型探讨

近30 a来冰川动力学模型有了快速发展, 在南极、 格林兰冰盖预测中取得一系列重要成果, 对山地冰川的研究也初见端倪. 从冰川流动的力学过程出发, 利用本构方程、 理想冰川假设、 浅冰层近似(Shallow ice approximation)假设完整地推导了理想冰川流动的物理过程, 揭示了冰川流动的机理, 建立了气候变化和冰川自身重力引起的理想冰川物质和能量再分配的温度耦合三维流动模型. 结合山地冰川的冰床形态, 将理想冰川与实际冰川相结合, 使理想冰川流动模型更好地近似山地冰川的流动.     

利用卫星遥感技术估算区域性海-气CO_2通量研究综述

海-气CO2通量的估算是碳循环研究的重要内容。随着卫星遥感技术的发展和外推算法的不断改进,基于海表层水CO2分压的调控影响因子,在不同的海域发展了不同参数的海表p CO2遥感外推算法,获得了区域性多时空尺度长时间序列的海域碳"源-汇"时空变化特征。本文针对单参数算法、双参数算法和多参数算法的发展过程和存在问题,综述了主要海区海-气CO2通量遥感外推算法的研究现状,并评述了在南大洋和北极海域利用遥感算法进行海-气CO2通量研究的应用。     

塔克拉玛干沙漠腹地地表辐射与能量平衡

利用2013年塔克拉玛干沙漠塔中流动沙面地表辐射、土壤热通量、土壤温湿度和湍流通量观测资料,分析了沙漠腹地地表辐射和能量收支特征及闭合状况。结果表明：除潜热通量外,其余地表辐射各分量和能量平衡分量的月平均日变化结果整体均表现为标准的单峰型日循环形态,其中R_s↓与R_s↑变化同步,R_l↑、R_l↓滞后R_s↓0.5 ~ 1 h。各分量均表现出夏季高、春秋季次之、冬季低的季节波动性。干旱和极低的植被覆盖造成沙漠腹地全年潜热通量始终较为微弱,约占净辐射的2.8%,感热通量成为能量的主要消耗形式,约占净辐射的49%。偶尔的降水会刺激潜热通量突然增加。地表反照率相对较高且稳定,日变化呈早晚大、正午小的“U”型趋势,并具有明显的冬季高、夏季低的季节波动性,年均值0.28,月均值0.25~0.32。能量残差各月的日变化也均呈单峰曲线,日出后和日落前能量闭合程度最佳,并出现过闭合现象,全年夏季小,春秋季次之,冬季较大,月平均日峰值5.1~99.9 W·m^-2。土壤表层热储存是影响该地区能量平衡的重要因子之一,考虑表层土壤热存储后,地表能量闭合率达75.3%,能量闭合率夏季 > 春季 > 秋季 > 冬季,白天相比夜间有大幅提升。     

A near‐annual palaeohydrological study based on testate amoebae from a sub‐alpine mire: surface wetness and the role of climate during the instrumental period

We present the first testate amoeba‐based palaeohydrological reconstruction from the Swiss Alps, and the first depth to the water table (DWT) calibration dataset for this region. Compared to existing models, our new calibration dataset performs well (RMSEP = 4.88), despite the length of the water table gradient covered (53 cm). The present‐day topography and vegetation of the study mire Mauntschas suggest that it is partly ombrotrophic (large Sphagnum fuscum hummocks, one of which was the coring site) but mostly under the minerotrophic influence of springs in the mire and runoff from the surrounding area. Ombrotrophic Sphagnum fuscum hummocks developed at the sampling site only during the last 50 years, when testate amoebae indicate a shift towards dry and/or acid conditions. Prior to AD 1950 the water table was much higher, suggesting that the influence of the mineral‐rich water prevented the development of ombrotrophic hummocks. The reconstructed DWT correlated with Pinus cembra pollen accumulation rates, suggesting that testate amoebae living on the mire and P. cembra growing outside of it partly respond to the same factor(s). Finally, temperature trends from the nearby meteorological station paralleled trends in reconstructed DWT. However, contrary to other studies made on raised bogs of northwestern Europe, the highest correlation was observed for winter temperature, despite the fact that testate amoebae would more logically respond to moisture conditions during the growing season. The observed correlation with winter temperature might reflect a control of winter severity on surface moisture during at least the first part of the growing season, through snow melt and soil frost phenomena influencing run‐off. More ecohydrological work on sub‐alpine mires is needed to understand the relationships between climate, testate amoebae and peatland development. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermal Backstripping from Vitrinite Reflectance Profiles in Comparison with an Extensional Model for Passive Continental Margin Basins on Northern Continental Shelf of South China Sea

INTRODUCTIONVitrinitereflectance(R.)canprovideagreatdealinfor-mationonthermalhistoryofabasin.Itisafunctionofmaximumpaleotemperatureandeffectiveheatingtime,inotherwords,afunctionofdepositionalrateandgeothermalgradientwithirreversiblecharacteristics.Butitalsohasacumulativeeffectthroughoutgeothermalevents.Paleotemperaturesaremainlycontro1ledbythebasalheatflowandheatgenerationfromradioactivesourceswithinthecrust.Themodelforde-terminingpaleoheatflowoflinearchangewithtimefr0mvitri-nitereflecta…     

东南极Lambert冰川-Amery冰架系统平衡通量分布的计算

通过对Lambert冰川盆地(LGB)考察路线上约1 700 km长的LGB剖面和距冰架末端约50 km、长150 km的A剖面, 分别利用GPS冰流速值及雷达测厚值进行冰通量的计算得出:每年流过LGB剖面的冰通量为43.95 Gta-1, 而通过A剖面的冰通量仅为26. 42 Gt*a-1, Amery冰架底部净融化量为7.8 Gt*a-1. 整个Lambert冰川-Amery冰架系统(LAS)地区的表面净物质平衡总量约为90 Gt*a-1; LGB地区的表面净物质平衡总量为46 Gt*a-1. 通过分析得出, 整个LAS地区及LGB地区均处于物质正平衡状态, 而LAS流域的上游区域S'则处于物质负平衡状态.     

长江河口区上段水、悬沙通量及其对北支演化的意义

2007年9月在长江河口3条控制断面的全潮观测结果表明,长江口南支均以落潮流和落潮输沙占优,而北支大、小潮期间的水沙输运特征迥异; 其特征与长江径流、河口地形地貌特征密切相关。小潮期间,长江口北支以落潮流占优; 大潮期间,则以涨潮流占优,且悬沙输运率比小潮期间增大一个数量级。分析结果进一步表明,从1958年至今,长江口北支的分流比呈下降的趋势,已由11.8% 降至目前的1.9%; 长江口北支也由早期的悬沙输入(与径流方向相反)通道变为输出通道,目前其分沙比仍达6.4% ~7.9% 左右。总体上,分流分沙比呈显著减小趋势,这是长江口北支萎缩的重要特征之一。此外,北支分沙比显著大于分流比,将可能造成北支的进一步淤积。     

祁连山疏勒河上游多年冻土区高寒草甸土壤CO2通量特征

研究青藏高原多年冻土区高寒草甸土壤CO₂通量有助于准确估算该区域的土壤CO₂排放, 对认识高原土壤碳循环及其对全球气候变化的响应具有重要意义. 利用静态箱-气相色谱法和LI-8100土壤CO₂通量自动测量系统对疏勒河上游多年冻土区高寒草甸土壤CO₂通量进行了定期观测, 结合气象和土壤环境因子进行了分析. 结果表明: 整个观测期高寒草甸土壤表现为CO₂的源, 土壤CO₂通量的日变化范围为2.52～532.81 mg·m^-2·h^-1. 土壤CO₂年排放总量为1 429.88 g·m^-2, 年均通量为163.23 mg·m^-2·h^-1; 其中, CO₂通量与空气温度和相对湿度、活动层表层2 cm、10 cm、20 cm、30 cm 土壤温度、含水量和盐分均显著相关. 2 cm土壤温度、空气温度和总辐射、空气温度、2 cm土壤盐分分别是影响活动层表层2 cm土壤完全融化期、冻结过程期、完全冻结期、融化过程期土壤CO₂通量的最重要因子. 在完全融化期、冻结过程期和整个观测期, 拟合最佳的温度因子变化分别能够解释土壤CO₂通量变化的72.0%、82.0%和38.0%, 对应的Q₁₀值分别为1.93、6.62和2.09. 冻融期(含融化过程期和冻结过程期)和完全冻结期的土壤CO₂排放量分别占年排放总量的15.35%和11.04%, 在年排放总量估算中不容忽视.     

Dynamics of seasonal recharge beneath a semiarid vegetation on the gnangara mound,Western Australia

To estimate seasonal changes in recharge to the underlying sandy aquifer, the soil water dynamics of the unsaturated zone was monitored down to a depth of 20 m over a period of three years (1985 to 1987). The measurements were made by a neutron probe at eight locations beneath a native vegetation in a semiarid region, Western Australia, receiving precipitation of 775 mm yr^?1. A relatively simple method, based on the analyses of sequentially measured soil water profiles involving utilization of zero flux plane in the unsaturated zone, is presented and used to compute seasonal recharge rates. Drainage fluxes (recharge rates) below two specified depths were estimated. These were: R₁ (water flux at a depth of 10 m, just below the maximum rooting depth) and R₂ (water flux at a depth of 18 m, just above the water table). These two estimates were significantly different both on a seasonal and annual basis, but their cumulative values for the three year period were very similar. While the annual precipitation varied from 525 to 850 mm yr^?1, the corresponding spatially averaged R₁ varied from 34 to 149 mm yr^?1, and R₂ varied from 65 to 80 mm yr^?1. A significant difference in recharge between the upslope and downslope positions on a hillslope was ascribed to differences in vegetation density of the understorey and differences in hydraulic properties of subsoils. For the three year period, the average R₁ and R₂ were 13 per cent and 10 per cent of the precipitation respectively. These values compare favourably with a long-term estimate based on an environmental tracer technique.