利用SEBAL和改进的SEBAL模型估算黑河中游戈壁、绿洲的蒸散发

蒸散发是干旱、半干旱地区内陆河流域水分消耗的主要途径, 利用遥感估算流域尺度上的蒸散发对内陆河流域水循环和水资源的合理利用具有重要的指导意义. 基于2012年开展的黑河流域生态-水文过程综合遥感观测联合试验(HiWATER)的观测资料和高分辨率的ASTER影像, 分别利用 SEBAL 模型和改进的SEBAL(M-SEBAL)模型估算黑河中游不同时期戈壁、绿洲等不同下垫面的蒸散发, 通过涡动观测数据对比分析了SEBAL模型和M-SEBAL模型估算戈壁、绿洲蒸散发的精度. 结果表明: SEBAL模型在绿洲低估感热通量, 高估潜热通量; 在戈壁高估感热通量, 低估潜热通量. M-SEBAL 模型充分考虑不同下垫面地表辐射温度与植被覆盖度之间的关系, 能很好地反映不同植被覆盖区域的湍流通量的异质性, 估算黑河中游戈壁、绿洲蒸散发的精度高于SEBAL模型.     

黑河流域山前绿洲水量转化模拟研究

利用数字高程数据、遥感解译成果、地下水和水文气象资料,建立了一个基于GIS网格的黑河中游山前绿洲地区分布式水文模型.模拟结果表明,黑河流域中游山前绿洲地带的降水几乎完全消耗于蒸散发,且大约70%的山区地表径流补给也消耗于蒸散发.蒸散发以中游森林为最多,草本植被蒸散发同植被覆盖度呈正比.天然植被覆盖度同降水量的多少呈正比,在当地气候条件下,降水是天然荒漠植被类型和分布的控制因子.     

大气CO2浓度增加对中国区域植被蒸腾的影响

近几十年来,人类活动带来的化石燃料燃烧和工业过程引起了全球大气CO2浓度的显著增长,带来了一系列生态和环境问题,其中对地表蒸散发的影响就是一个重要方面.地表蒸散发及其分量植被蒸腾是能量和水量平衡的重要组分,直接影响着陆气相互作用和水循环系统.由于大气CO2浓度增加可通过减小叶片气孔导度从而抑制植被蒸腾,为量化这一影响,基于碳水耦合的蒸散发模型PML-V2和CMIP6的大气CO2浓度时空序列驱动数据,分别进行了考虑和不考虑大气CO2浓度逐年增加情况下的2组植被蒸腾模拟试验.通过对比2组结果分析了2001-2014年大气CO2浓度增加对中国区域植被蒸腾的影响.研究结果显示,在季节上,夏季大气CO2浓度增加对植被蒸腾的抑制作用最小,冬季最大;在数量级上,2001-2014年大气CO2浓度引起植被蒸腾变化在0～5％;不同生态系统比较而言,森林、耕地和灌丛生态系统受CO2浓度增加引起植被蒸腾的减小量较大,14年间减小量为15～20mm/a,而草地下降最小,约5 mm/a;在空间上,我国中东部受影响最大;CO2浓度引起植被蒸腾变化最敏感的区域是我国东南部地区.     

基于水文模型的蒸散发数据同化实验研究

流域蒸散发定量估算一直是水科学领域的研究前沿,水文模型和遥感反演是当前估算区域蒸散发的常用手段。研究通过数据同化,集成水文模型和遥感模型的优势,耦合遥感蒸散发到水文模型中以实现多源数据下的蒸散发数据同化。选择北京市沙河流域为研究区,分布式时变增益水文模型作为模型算子,基于集合卡尔曼滤波同化算法,利用双层遥感模型模拟的蒸散发同化水文模型,并基于地面通量站观测的日蒸散发进行验证。结果表明,同化结果与观测数据相比平均绝对百分比误差较同化前减少,精度进一步提升,且当遥感观测输入频繁时精度改善明显。研究证明基于水文模型的蒸散发数据同化系统,是一种可实现输出精度更高和时序连续的区域蒸散发的新型模式。该成果将进一步丰富创新蒸散发估算的学科内容,为准确理解区域水循环规律提供科学依据。     

青藏高原净生态系统碳交换量的遥感评估模型研究

青藏高原作为世界海拔最高的区域,是全球气候变化的敏感区之一。定量估算这一区域的净生态系统碳交换量(NEE)有利于理解陆地生态系统碳平衡对未来气候变化的响应。本文构建了一个模拟该地区NEE动态变化的净碳收支模型(NCBM)。该模型由来源于MODIS影像的增强型植被指数(EVI)、陆地表面水分指数(LSWI)以及来源于地面观测的空气温度和短波辐射共同驱动,并利用青藏高原地区的3种植被类型(包括高寒灌丛、高寒湿地和高寒草甸)的碳通量长期观测数据对模型进行了校准和验证。结果表明,在模型校准站点年,NCBM模型可以模拟NEE观测值81%的变化,均方根误差(RMSE)为0.03mol C/m~2/d,模型效率(EF)为0.81。在模型验证站点年,NCBM模型可以预测NEE观测值84%的变化,RMSE为0.03mol C/m~2/d,EF为0.81。在大多数情况下,NCBM模型可以清晰地模拟各植被类型的NEE季节和年际变化。此外,NCBM模型因为结构简单,模型驱动变量易于获取等优势,具有在区域尺度上模拟NEE时空变化的潜力。但是该模型还需要进一步的改进和发展,特别需要提高对植被非常稀疏地区NEE变化的模拟能力。     

CLM5.0对高寒山区蒸散发模拟的适用性评估北大核心CSCD

蒸散发是地表水文循环和能量交换过程的重要组成部分,且在高寒山区有极强的时空异质性,准确模拟蒸散发对于研究高寒山区水文循环过程有着重要的意义。CLM5.0(Community Land Model5.0)是CLM模式的最新版本,具有较为完善的水文循环机制,是目前国际上发展最为完善的陆面过程模式之一。基于典型高寒山区黑河上游五个观测站的观测数据,对CLM5.0的蒸散发模拟性能进行评估。结果表明:CLM5.0在模拟蒸散发时结果总体上可信,其R值的范围在0.601~0.839之间,RSR值的范围在0.964~1.145之间,BIAS值的范围在^(-1).220~-0.597 mm·d^(-1)之间。说明CLM5.0在高寒山区可以较好地捕捉观测到蒸散发的时间趋势,但仍存在一定的低估。非生长季的BIAS值的范围在-0.904~-0.367 mm·d^(-1)之间,生长季的BIAS值的范围在-2.094~-0.794 mm·d^(-1)之间,这表明蒸散发模拟值的低估主要来自生长季的模拟。高寒草甸上R值的范围在0.299~0.651之间,RSR值的范围在1.135~1.332之间,高寒草地上R值为0.209,RSR值为1.450,因此,CLM5.0在草甸的模拟性能优于草地。CLM5.0白天R值的范围在0.605~0.840之间,RSR值的范围在0.252~1.193之间,夜晚R值的范围在0.344~0.651之间,RSR值的范围在0.482~2.966之间,对比可知CLM5.0在白天模拟蒸散发的性能优于夜晚。这些结论可为CLM5.0的应用和改进提供科学依据。     

基于涡动相关仪验证的SEBS模型对黑河中游地表蒸散发的估算研究

在我国西北干旱和半干旱地区, 农业收获主要依靠灌溉保证, 灌溉绿洲的蒸散发(ET)是当地水资源的主要消耗. 通过遥感估算区域灌溉绿洲的ET对于地区合理利用水资源极其重要, 利用MODIS/Terra 影像, 基于物理过程的地表能量平衡模型(SEBS), 结合WRF模式输出的气候驱动数据和地面观测数据来估算黑河中游地区的地表通量和日蒸散发(ET_daily). 估算的ET用不同下垫面的涡动相关仪观测数据进行验证, 结果显示: SEBS模型估算的不同下垫面的ET_daily具有很好的拟合效果(R²=0.96, P<0.001), 在灌溉绿洲估算的ET_daily比实测值偏高, 说明干旱、半干旱地区灌溉绿洲土壤水分胁迫是影响ET的主要因素. 模型估算绿洲作物生长期间的ET_daily和实测的ET_daily平均相对误差为12.5%, 精度在观测的能量不闭合误差以内且精度比戈壁和沙漠地区高.     

基于土壤植被不同参数化方法的流域蒸散发模拟

植被和土壤是水循环中的重要载体,模拟流域水循环时植被和土壤的参数化也显得尤为重要。通过对比流域蒸散发模拟中分布式模型和集总式概念模型的土壤植被参数化方法,计算了潘家口水库流域不同时间尺度上的流域蒸散发,分析了不同时间尺度下流域蒸散发的影响因素。通过分析得出:(1)分布式水文模型中的植被参数化方法包括对植被时空分布与变化的描述,以及与之相关的土壤-植被-大气中水分和能量的传输过程的描述。(2)从GBHM模型与流域水热耦合平衡模型的对比分析可知,在流域尺度上,年实际蒸散发与潜在蒸散发之间呈互补的高度非线性关系;但在山坡和小时时间尺度上,实际蒸散发与潜在蒸散发之间呈正比关系,并可近似为线性正比关系。(3)基于流域水热耦合平衡模型在不同时间尺度的参数化分析可知,考虑植被土壤水分和植被覆盖度能改善对流域蒸散发的年际和季节变化的模拟精度;土壤水分和植被的影响随着时间尺度变小表现得越来越显著。     

塔里木河下游胡杨林耗水数值模型

基于SHAW（Simultaneous Heat and Water）模型,以基本观测要素、植被参数和土壤剖面水热观测数据为模型的输入,对河岸胡杨林的耗水过程、土壤剖面水分变化和能通量进行了较小时间尺度上的模拟研究。结果表明,采用SHAW模型模拟的胡杨耗水量与观测值间存在较大偏差。因此,为了进一步提升水热耦合SHAW模型在干旱区的实用性,引入了地下水位因子GSI（Groundwater-Soil water Interaction）,建立了改进的SHAW（GSI-SHAW）模型,解决干旱区荒漠河岸林耗水过程模拟的方法问题。采用SHAW模型和GSI-SHAW模型对胡杨耗水量的模拟进行了对比研究。结果显示,SHAW模型和GSI-SHAW模型模拟的胡杨耗水量与观测值的相关性系数分别为0.8533、0.9075,其平均相对误差分别为21.4%、16.9%,可见,改进的SHAW模型的模拟值更加接近试验观测值。地下水位的考虑一定程度上提升了传统SHAW模型的模拟精度,为干旱区自然植被耗水量的计算提供了新的方法和科学依据。     

基于蒸散发数据同化的径流过程模拟

采用集合卡尔曼滤波算法,以遥感反演的蒸散发作为观测数据,构建一种基于新安江模型的蒸散发同化系统;根据同化后的蒸散发,采用粒子群算法估计新安江模型的土壤张力水蓄量,进而改进模型的径流模拟效果。选取地表能量平衡系统模型进行汉江流域蒸散发（ET_SEBS）反演,采用基于GRACE水储量距平数据的水量平衡蒸散发（ET_GRACE）进行验证,结果显示ET_SEBS总体表现好于蒸散发产品ET_GLDAS、ET_Zhang、ET_MODIS,且相关系数（R）、均方根误差（E_RMS）、偏差（B）为0.93、11.93 mm/月、-3.47 mm/月,表明SEBS模型能够较好地估算蒸散发。将同化方案在旬河流域进行应用,结果显示同化后径流的纳什效率系数（E_NS）为0.85,较同化前0.81明显提高,且模型对枯水期径流的低估问题有一定改善,对径流峰值模拟效果提高明显。     

Long-term Trends in Vegetation Dynamics and Forest Fires in Brandenburg (Germany) Under a Changing Climate

The human influence on environmental processes has been described for many types of land use. One of the oldest tools to modify people’s environment is fire, which has dominated fire regimes in many regions over long time scales. This paper focuses on a German case study region, where 80–90% of the fires are human-caused. The objectives of this study are the application of the Regional Fire Model (Reg-FIRM), a process-based fire model that is incorporated into the LPJ Dynamic Global Vegetation Model, to temperate forests under historic climate conditions and to explore ranges of potential impacts of future climate change on fire and vegetation dynamics. Simulation experiments are designed to simulate historic fire pattern and to explore influences of vegetation on fire. Simulated fire pattern reproduced the observed average fire conditions reasonably well although with a smaller amplitude. This leads to underestimation of extreme fire years as well as an overestimation of low fire years. Vegetation composition influenced fire spread conditions in the temperate forest and had little impact on fire ignition potentials, except when only broad-leaved deciduous forests were assumed. Fire is likely to change under climate change conditions. Simulated experiments were conducted to explore the effects of climate change and rising CO₂ concentration given the potential natural vegetation as the best-case for Brandenburg. Three GCM scenarios predicting different future climatic changes were applied, and resulted in quantitatively different future fire patterns. Depending on future precipitation pattern and the influence of the CO₂ effect on canopy conductance and thus litter moisture, fire was predicted to either decrease or slightly increase in Brandenburg forests, but the burnt area would not exceed current, extreme fire years. Generally, fire changes had no implication for vegetation composition in Brandenburg, but reduced vegetation carbon gain after 2050. In the HadCM3 application, simulated increase in grass cover due to a large burnt area after 2075 accelerated fire spread conditions, thus still increasing the burnt area, while climatic fire danger and number of fires already began to decline. These interactions underline the importance to consider the full range of fire processes and interactions with vegetation dynamics in a simulation model.     

九寨沟水环境灰色系统动态模型

在充分了解九寨沟地区地质、水文地质的基础上，本文充分利用已监测的数据资料构建了九寨沟水环境灰色系统动态预测模型，对该区水环境变化趋势进行了预测评价。     

GM（1，1）模型预测地下水位时间序列应用研究

在灰色理论基础上,详细阐述了地下水水位时间序列GM（1,1）动态模型的建立过程。以无锡市为例,对模型进行了评定和检验。结果表明,模型的预测精度较高,具有一定的实用价值。     

考虑降水预报的三峡入库洪水集合概率预报方法比较

为了考虑预见期内降水预报的不确定性对洪水预报的影响,采用中国气象局、美国环境预测中心和欧洲中期天气预报中心的TIGGE(THORPEX Interactive Grand Global Ensemble)降水预报数据驱动GR4J水文模型,开展三峡入库洪水集合概率预报,分析比较BMA、Copula-BMA、EMOS、M-BMA 4种统计后处理方法的有效性。结果表明:4种统计后处理方法均能提供一个合理可靠的预报置信区间;其期望值预报精度相较于确定性预报有所提高,尤其是水量误差显著减小;M-BMA方法概率预报效果最佳,它能够考虑预报分布的异方差性,不需要进行正态变换,结构简单,应用灵活。     

国外空域资源开发利用的理论基础、方法论变革与实践

空中交通流量的持续增长引发充分开发利用空域资源的理论建设和方法论研究及其应用实践,旨在突破原有的空域结构及其扇区边界的限制。在过去的10年里航线结构及其需求有了显著变化,仍保持相对固定的几何扇区形态面临新的挑战,需要重新设计动态空域功能分区。首先分析了当前空域资源开发利用的理论基础,包括新一代航空运输体系,灵活空域使用,平衡扇区等;然后评价了方法论的变革,总结了从动态空域配置(DAC)到动态空域功能分区(DAS)的转变,以及动态空域功能分区的2D-DAS常用方法向3D-DAS新方法的演进,并讨论了"基于个体模型"(ABM)的局限性和"改进的基于个体模型"(i ABM)的应用优势;最后展望了地理学空间研究向空域拓展的前景。     

Different ways to handle topography in practical geoid determination

In this paper two different methods of how to handle topography in geoid determination is investigated. First method employs the Residual Terrain Model (RTM) remove-restore technique and yields the quasigeoid, whereas the second method is the classical Helmert condensation method, yielding the geoid. Both methods were used with the Earth Gravity Model (1996) (EGM96) geopotential model as reference, and results are compared to precise Global Positioning System (GPS) levelling networks in Scandinavia, especially an accurate GPS data set from the very rugged Sognefjord region, where the topography was represented by either a detailed (100 m) or a coarse (1000 m) digital terrain model. The inclusion of bathymetry in the terrain model was also investigated.Even if two different methods were used, they produced almost identical results at the 5 cm level in the mountains, but small systematic differences exist. Results show the importance of comparing the right types of geoid (classical geoid or quasigeoid), since differences in residuals are significant.     

Impacts of climate change on the hydro-climatology of the upper Ishikari river basin,Japan

Evidence for climate change impacts on the hydro-climatology of Japan is plentiful. The objective of the present study was to evaluate the impacts of possible future climate change scenarios on the hydro-climatology of the upper Ishikari River basin, Hokkaido, Japan. The Soil and Water Assessment Tool was set up, calibrated, and validated for the hydrological modeling of the study area. The Statistical DownScaling Model version 4.2 was used to downscale the large-scale Hadley Centre Climate Model 3 Global Circulation Model A2 and B2 scenarios data into finer scale resolution. After model calibration and testing of the downscaling procedure, the SDSM-downscaled climate outputs were used as an input to run the calibrated SWAT model for the three future periods: 2030s (2020–2039), 2060s (2050–2069), and 2090s (2080–2099). The period 1981–2000 was taken as the baseline period against which comparison was made. Results showed that the average annual maximum temperature might increase by 1.80 and 2.01, 3.41 and 3.12, and 5.69 and 3.76 °C, the average annual minimum temperature might increase by 1.41 and 1.49, 2.60 and 2.34, and 4.20 and 2.93 °C, and the average annual precipitation might decrease by 5.78 and 8.08, 10.18 and 12.89, and 17.92 and 11.23% in 2030s, 2060s, and 2090s for A2a and B2a emission scenarios, respectively. The annual mean streamflow may increase for the all three future periods except the 2090s under the A2a scenario. Among them, the largest increase is possibly observed in the 2030s for A2a scenario, up to approximately 7.56%. Uncertainties were found within the GCM, the downscaling method, and the hydrological model itself, which were probably enlarged because only one single GCM (HaDCM3) was used in this study.     

Spatial aspects of building and population exposure data and their implications for global earthquake exposure modeling

This paper discusses spatial aspects of the global exposure dataset and mapping needs for earthquake risk assessment. We discuss this in the context of development of a Global Exposure Database for the Global Earthquake Model (GED4GEM), which requires compilation of a multi-scale inventory of assets at risk, for example, buildings, populations, and economic exposure. After defining the relevant spatial and geographic scales of interest, different procedures are proposed to disaggregate coarse-resolution data, to map them, and if necessary to infer missing data by using proxies. We discuss the advantages and limitations of these methodologies and detail the potentials of utilizing remote-sensing data. The latter is used especially to homogenize an existing coarser dataset and, where possible, replace it with detailed information extracted from remote sensing using the built-up indicators for different environments. Present research shows that the spatial aspects of earthquake risk computation are tightly connected with the availability of datasets of the resolution necessary for producing sufficiently detailed exposure. The global exposure database designed by the GED4GEM project is able to manage datasets and queries of multiple spatial scales.     

Scale effects of eroded sediment transport in Wujiang River Basin,Guizhou Province,China

In recent years, research on spatial scale and scale transformation of eroded sediment transport has become a forefront field in current soil erosion research, but there are very few studies on the scale effect problem in Karst regions of China. Here we quantitatively extracted five main factors influencing soil erosion, namely rainfall erosivity, soil erodibility, vegetative cover and management, soil and water conservation, and slope length and steepness. Regression relations were built between these factors and also the sediment transport modulus and drainage area, so as to initially analyze and discuss scale effects on sediment transport in the Wujiang River Basin (WRB). The size and extent of soil erosion influencing factors in the WRB were gauged from: Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM), precipitation data, land use, soil type and Normalized Difference Vegetation Index (NDVI) data from Global Inventory Modeling and Mapping Studies (GIMMS) or Advanced Very High Resolution Radiometer (AVHRR), and observed data from hydrometric stations. We find that scaling effects exist between the sediment transport modulus and the drainage area. Scaling effects are expressed after logarithmic transformation by a quadratic function regression relationship where the sediment transport modulus increases before decreasing, alongside changes in the drainage area. Among the five factors influencing soil erosion, slope length and steepness increases first and then decreases, alongside changes in the drainage area, and are the main factors determining the relationship between sediment transport modulus and drainage area. To eliminate the influence of scale effects on our results, we mapped the sediment yield modulus of the entire WRB, adopting a 1 000 km2 standard area with a smaller fitting error for all sub-basins, and using the common Kriging interpolation method.     

新一轮全球地球化学填图:中国的机遇和挑战

论述从1988年联合国教科文组织相继批准实施国际地球化学填图(IGCP259)和全球地球化学基准(IGCP360)项目以来,中国和欧洲在制定全球地球化学填图的方法指南及技术标准方面作出的决定性贡献。文中指出,中国的"环境地球化学监控网络及动态地球化学填图"项目、欧洲的FOREGS地球化学基准值填图项目为全球其他国家开展类似工作提供了示范,但地球化学家预期10年内获得全球地表地球化学概貌的愿望至今未能实现。挪威和中国的地球化学家通过IAHS/ICCE正在酝酿"Global geochemical mapping and the sediment-bound flux of major world rivers"重大国际合作项目,以开展新一轮全球地球化学填图。通过国际极地年,IPY317项目首先从北极地区启动。新一轮全球地球化学填图项目计划以中国提出的"全球地球化学填图的泛滥平原沉积物采样草案"和挪威提出的"三角洲中河漫滩沉积物的采样草案"作为实施方案,因而巩固和扩大了中国地球化学填图技术在全球的优势地位。论文在分析中国面临的机遇与挑战后,建议政府主管部门对新一轮全球地球化学填图给予优先支持。