Investigation of the Co-seismic Gravity Field Variations Caused by the 2004 Sumatra-Andaman Earthquake Using Monthly GRACE Data

Gravity Recovery and Climate Experiment(GRACE) observations have been used to de-tect the co-seismic and post-seismic gravity field variations due to the Mw=9.3 Sumatra-Andaman earthquake that occurred on December 26,2004.This article focuses on investigating some gravita-tional effects caused by this huge earthquake.We computed the geoid height changes,the equivalent water height(EWH) changes,and the gravity changes using the GRACE Level-2 monthly spherical harmonic(SH) solutions released by University of ...     

中国大型水库蓄水对近海相对海平面空间变化的影响

通过对我国大型水库蓄水的时空特征进行深入分析, 统计得到近60年来大型水库蓄水累积的库容量已达到697km3, 占全国所有水库库容量的83.3%及全球库容量的6.5%;而2000年以来的大型水库数量及蓄水量的变化有明显的加速, 库容量的变化率为16.7km3/a, 远高于1950年到2000年的4.9km3/a的增长率; 同时借助卫星重力(Gravity Recovery and Climate Experiment, GRACE)观测手段, 对2000年以后主要分布在长江流域以南地区的水库进行水储量估算, 结果显示GRACE仅能估算得到63%的水库变化量, 两者之间的差异可能反映了该地区地下水的长期变化. 结合大型水库的分布位置与库容量, 基于海平面变化方程计算得到了中国近海相对海平面的空间变化. 水库蓄水导致的渤海与东南沿海海域的相对海平面上升明显, 最大上升高度约为8mm; 而2000年以后的水库对海平面的影响主要集中在东南沿海, 其中南海海域较为突出, 上升高度约为2~3mm, 在此期间蓄水造成的近海不同验潮站位置的海平面增长速度在0.02~0.11mm/a之间变化.      

基于GRACE卫星测量得到的中国及其周边地区陆地水量变化

GRACE卫星成功开辟了空间大地测量对地观测的新途径。利用GRACE卫星得到的时变地球重力资料,分析估计了中国及其周边地区陆地水量的变化趋势,较为清晰地揭示了该地区季节性变化特征。进一步采用13点滑动平均的方法扣除了季节性变化,提取了4个特征区域(喜马拉雅南部,新疆与西藏及其周边的亚洲高山区域,中国华北、东北地区和中国南部地区)的陆地水量变化特征信息,这4个区域陆地水量的变化趋势分别为-12.7±0.7、-60.4±2.7、-12.5±0.5和6.6±0.9 km³/a。其中：喜马拉雅南部和亚洲高山区域陆地水量呈现明显的衰减趋势,与Matsuo和Heki模拟冰川质量损失源得到的结果较为一致;但近10年来亚洲高山区域西北部冰川加速融化趋势并不明显。中国华北、东北地区和南部地区水量变化比较复杂,具不稳定的变化趋势。     

Mapping groundwater storage variations with GRACE: a case study in Alberta,Canada

The applicability of the Gravity Recovery and Climate Experiment (GRACE) to adequately represent broad-scale patterns of groundwater storage (GWS) variations and observed trends in groundwater-monitoring well levels (GWWL) is examined in the Canadian province of Alberta. GWS variations are derived over Alberta for the period 2002–2014 using the Release 05 (RL05) monthly GRACE gravity models and the Global Land Data Assimilation System (GLDAS) land-surface models. Twelve mean monthly GWS variation maps are generated from the 139 monthly GWS variation grids to characterize the annual GWS variation pattern. These maps show that, overall, GWS increases from February to June, and decreases from July to October, and slightly increases from November to December. For 2002–2014, the GWS showed a positive trend which increases from west to east with a mean value of 12 mm/year over the province. The resulting GWS variations are validated using GWWLs in the province. For the purpose of validation, a GRACE total water storage (TWS)-based correlation criterion is introduced to identify groundwater wells which adequately represent the regional GWS variations. GWWLs at 36 wells were found to correlate with both the GRACE TWS and GWS variations. A factor f is defined to up-scale the GWWL variations at the identified wells to the GRACE-scale GWS variations. It is concluded that the GWS variations can be mapped by GRACE and the GLDAS models in some situations, thus demonstrating the conditions where GWS variations can be detected by GRACE in Alberta.     

基于GRACE 和GLDAS 的塔里木河流域地下水储量演变规律研究

塔里木河流域位于中国西北干旱区,降水稀少,生态脆弱,水资源是维系当地社会经济发展和生态健康的关键因素。文章利用GRACE重力卫星数据和GLDAS全球陆面同化系统数据识别了塔里木河流域2003~2019年地下水储量变化,并分析其时空分布规律。结果显示,2003~2019年间塔里木河流域地下水储量整体呈下降趋势,速率为-2.13 mm/a。在空间分布上,由北向南,地下水储量的下降降幅逐渐减少,天山南坡中段地区地下水亏损最大,而塔里木河下游地下水储量稳步回升,与近十多年的应急生态输水有关。此外,塔里木河流域地下水储量变化与年降水量存在比较一致的年际变化特征。2004、2006~2009年降水量偏少,地下水储量显著减少,降水量多的年份,地下水储量出现回升。基于GRACE和GLDAS的地下水储量分析方法对于对监测缺乏地下水站网的塔里木河流域地下水资源具有较大应用潜力。     

Regional lithofacies and pedofacies variations along a north to south climatic gradient during the Last Glacial period in the central Loess Plateau,China

Five lateral sand–loess–palaeosol continua occur within the last glacial sediments of the central Loess Plateau of China along a 500 km north to south climatic gradient. The continua shift southward or northward in concert with desert expansion or contraction, respectively. Lateral lithofacies (desert sand to loess) variations are evident at the north end of the gradient and follow Walther's Law of the correlation of facies. Lateral pedofacies (loess to palaeosol) variations are present near the south end of the gradient, where the climate was warmer and wetter. The lateral stratigraphic changes from sand to loess or loess to soil are driven by variations in the rate of sedimentation along a climatic gradient.Vertical stratigraphic profiles at the north end of the gradient reveal alternating sand and loess beds. In contrast, alternating loess and palaeosols occur within the same stratigraphic interval in the southern Loess Plateau, where dust accretion rates were lower. However, in high resolution studies of climate change vertical profiles of alternating loess and palaeosols (especially weak palaeosols) may not reflect regional or global climate change. Alternating loess and weak palaeosols may reflect local variations in the balance between the rates of dust accretion and pedogenesis. Local fluctuations in either of these rates could result in the presence of time equivalent loess and palaeosols at high resolutions. Thus, some of the high resolution loess-palaeosol alternations may reflect local climatic variation rather than global or hemispherical climate change.     

Recent hydrological behavior of the East African great lakes region inferred from GRACE,satellite altimetry and rainfall observations

We have jointly analysed space gravimetry data from the GRACE space mission, satellite altimetry data and precipitation over the East African Great Lakes region, in order to study the spatiotemporal variability of hydrological parameters (total water storage, lake water volume and rainfall). We find that terrestrial water storage (TWS) from GRACE and precipitation display a common mode of variability at interannual time scale, with a minimum in late 2005, followed by a rise in 2006–2007. We argue that this event is due to forcing by the strong 2006 Indian Ocean Dipole (IOD) on East African rainfall. We also show that GRACE TWS is linked to the El Niño-Southern Oscillation cycle. Combination of the altimetry-based lake water volume with TWS from GRACE over the lakes drainage basins allows estimating soil moisture and groundwater volume variations. Comparison with the WGHM hydrological model outputs is performed and discussed.     

LGM时期气候背景下中国区域植被变化对东亚夏季降水影响的模拟

利用CCM3/NCAR全球气候模式在21kaB.P.(2.1万年前)的末次盛冰期(LGM)气候背景下,对中国区域植被变化对夏季(6～7月)东亚季风降水的影响进行了模拟,结果表明： 在LGM时期气候背景下,植被退化会使得中国东南部夏季降水减少,其中东南沿海减少超过20mm,而在 100°E 以东的中国北方大部分地区降水增加,其中心值大于50mm,从而导致降水南少北多的现象,植被的这种影响可以从物理上得到解释。在LGM气候背景下,植被退化在暖季起着增温的作用,即通过影响地表热状况使夏季大陆增温,增强了夏季东亚大陆与其周边海域的热力差异,从而使夏季东亚地区的西南风增强,35°～45°N的北方地区对流层低层的空气辐合和对流层上升运动加强,伴随着在 30°N 以南的中国南方地区出现异常下沉运动; 同时,西南季风的加强也导致夏季在 30°～40°N 之间的华北地区低层水汽输送加大。在这些因子的共同作用下,中国北方夏季降水增多,而东南部降水减少。这些结果说明使用LGM时期中国区域不同的重建植被资料可以对东亚季风气候模拟产生一定的不确定性。因此,重建可信度高的东亚植被对于降低对气候模拟的不确定性是十分重要的。     

青藏高原南部冰芯记录与大气环流的关系*

通过念青唐古拉峰拉弄冰川垭口处(30°24'30″N, 90°34'12″E;海拔5850m)长度为29.5m的冰芯记录,恢复了1952~1998年间大气降水δD和净积累量的时间变化序列。上述两组序列与NCEP/NCAR气候资料的相关分析表明:δD和净积累量与中亚冬季的气压、南亚和青藏高原冬季、夏季的位势高度关系密切。中亚地区冬季气压的升高以及冬、夏季南亚和青藏高原位势高度的异常增强了印度夏季风,导致了念青唐古拉峰地区20世纪80年代以来降水量的增多和降水中δD值的降低。根据念青唐古拉冰芯δD和净积累量记录及其与亚洲地区大气环流的关系,可以通过青藏高原南部较长的冰芯记录来恢复过去该地区大气环流变化的历史。     

Estimating groundwater storage changes in the Mississippi River basin (USA) using GRACE

Based on satellite observations of Earth’s time variable gravity field from the Gravity Recovery and Climate Experiment (GRACE), it is possible to derive variations in terrestrial water storage, which includes groundwater, soil moisture, and snow. Given auxiliary information on the latter two, one can estimate groundwater storage variations. GRACE may be the only hope for groundwater depletion assessments in data-poor regions of the world. In this study, soil moisture and snow were simulated by the Global Land Data Assimilation System (GLDAS) and used to isolate groundwater storage anomalies from GRACE water storage data for the Mississippi River basin and its four major sub-basins. Results were evaluated using water level records from 58 wells set in the unconfined aquifers of the basin. Uncertainty in the technique was also assessed. The GRACE-GLDAS estimates compared favorably with the well based time series for the Mississippi River basin and the two sub-basins that are larger than 900,000 km². The technique performed poorly for the two sub-basins that have areas of approximately 500,000 km². Continuing enhancement of the GRACE processing methods is likely to improve the skill of the technique in the future, while also increasing the temporal resolution.     

Present rate of uplift in Fennoscandia from GRACE and absolute gravimetry

Fennoscandia is a key region for studying effects of glacial isostatic adjustment. The associated mass variations can be detected by the Gravity Recovery and Climate Experiment (GRACE) satellite mission, which observes the Earth's gravity field since April 2002, as well as by absolute gravimetry field campaigns. Since 2003, annual absolute gravity (AG) measurements have been performed in Fennoscandia by the Institut für Erdmessung (IfE, Institute of Geodesy) of the Leibniz Universität Hannover, Germany, within a multi-national cooperation. This offers a unique opportunity for validation and evaluation of the GRACE results. In this preliminary study, the GRACE results are compared to secular gravity changes based on the surveys from 2004 to 2007 with the FG5-220 gravimeter of the IfE.The results from GRACE monthly solutions provided by different analysis centres show temporal gravity variations in Fennoscandia. The included secular variations are in good agreement with former studies. The uplift centre is located west of the Bothnian Bay, the whole uplift area comprises Northern Europe. Nevertheless, the differences between the GRACE solutions are larger than expected and the different centre-specific processing techniques have a very strong effect on possible interpretations of GRACE results. The comparison of GRACE to the AG measurements reveals that the determined trends fit well with results from GRACE at selected stations, especially for the solution provided by the GFZ. Variations of land hydrology clearly influence results from GRACE and the AG measurements.     

中亚干旱区陆地水资源对气候变化的响应

气候变化对中亚干旱区高山融雪、蒸散发以及径流等水循环过程产生影响,从而引起区域水资源在空间和时间上的重新分配.在归纳总结降水、土壤水、地表水、陆地水储量等不同水体类型在气候变化下改变情况的基础上,综述了中亚干旱区陆地水资源变化对气候变化响应的现状及进展.由于使用的数据和评估方法不同,水资源变化研究结果具有一致性及不确定...     

Identifying Water Storage Variation in Krishna Basin,India from <Emphasis Type="Italic">in situ</Emphasis> and Satellite based Hydrological Data

Terrestrial water storage (TWS), a sum total of water stored on or beneath the earth’s surface, transits in response to hydroclimatic processes such as precipitation, evapo-transpiration, runoff etc. and serves an indicator of hydrological condition of a region. We analyse spatio-temporal variance of water storage in Krishna Basin, India, derived from in-situ groundwater data and Gravity Recovery and Climate Experiment (GRACE) satellite data in order to determine physical causes of variations, and compare the variance with climatic factors such as Cumulative Rainfall Departure (CRD) and drought index i.e. Standardized Precipitation Index (SPI). GRACE satellite based TWS is found to reflect insitu groundwater changes and also shows a relationship with drought patterns as indicated by a good correlation with SPI. The largest part of TWS represents seasonal flux, and at an interannual scale, TWS depicts spatio-temporal variability in response to drought index viz. SPI. We infer that the groundwater storage derived from GRACE time-variable gravity solutions can be utilised to complement in-situ observations at basin scale and it reflects climatic forcing quite well.     

青藏高原东北侧夏季干旱的气象成因和长期预报研究

本文利用近40年(1950～1988年)的北太平洋月平均海温(SST)场、逐月南方涛动指数(SOI)和北半球100hPa月平均高度场,探讨影响黄土高原夏季干旱的信息区及其在时空上的遥相联系,发现热带地区(尤其是低纬地区)的SST和低层环流系统(如SO)的强弱变化与西北夏季干旱存在较好的遥相关,这种相关反映在前期各信息区内主要存在半年左右的时滞相关。又从能量频散角度讨论黑潮区SST变化与影响西北夏季干旱环流系统(南亚高压)之间的可能联系。结果得出对中国西北夏季干旱的长期预报,除应按常规注意中高纬度大气环流的变异外,还需要重视前期(冬末春初)热带地区SST与南方涛动的变异。     

Sensitivity of the Gravity Recovery and Climate Experiment (GRACE) to the complexity of aquifer systems for monitoring of groundwater

The Gravity Recovery and Climate Experiment (GRACE) satellite mission is aimed at assessment of groundwater storage under different terrestrial conditions. The main objective of the presented study is to highlight the significance of aquifer complexity to improve the performance of GRACE in monitoring groundwater. Vidarbha region of Maharashtra, central India, was selected as the study area for analysis, since the region comprises a simple aquifer system in the western region and a complex aquifer system in the eastern region. Groundwater-level-trend analyses of the different aquifer systems and spatial and temporal variation of the terrestrial water storage anomaly were studied to understand the groundwater scenario. GRACE and its field application involve selecting four pixels from the GRACE output with different aquifer systems, where each GRACE pixel encompasses 50–90 monitoring wells. Groundwater storage anomalies (GWSA) are derived for each pixel for the period 2002 to 2015 using the Release 05 (RL05) monthly GRACE gravity models and the Global Land Data Assimilation System (GLDAS) land-surface models (GWSA_GRACE) as well as the actual field data (GWSA_Actual). Correlation analysis between GWSA_GRACE and GWSA_Actual was performed using linear regression. The Pearson and Spearman methods show that the performance of GRACE is good in the region with simple aquifers; however, performance is poorer in the region with multiple aquifer systems. The study highlights the importance of incorporating the sensitivity of GRACE in estimation of groundwater storage in complex aquifer systems in future studies.     

亚洲特提斯域岩相古地理与油气聚集地质特征

亚洲特提斯域油气在地理上主要分布于西亚段南带,其次为西亚段北带、东南亚段中带,再次为中亚段。对古、中、新特提斯域的岩相古地理特征作了分析研究,并编制了相关的岩相古地理图。认为油气分布在盆地类型上主要与前陆盆地、克拉通边缘盆地相关,盆地形态主要与台地、环形坳陷、线形坳陷等沉积—构造环境相关,其成烃物质的沉积-构造环境多位于古赤道与45°古纬度之间。提出盆地保存是盆地油气评价的先决条件。指出了亚洲特提斯域南带、中带和北带的油气勘探新领域。     

Comparisons of drought variability between central High Asia and monsoonal Asia: Inferred from tree rings

Severe drought is a serious natural disaster that frequently strikes East Asia, highlighting the need to understanding its drought regime and the associations with Asian monsoon. Tree-ring-based drought reconstructions provide invaluable paleoclimatic archives for detecting regional and large-scale drought variability and their potential forcings. We herein reviewed many drought reconstructions from central High Asia and monsoonal Asia and compared their similarities and differences, as well as their linkages to Asia monsoon. We compared the decadal-scale variability of six drought reconstructions for the central High Asia, where differing drought variations were found between the western and eastern portions. Seven drought reconstructions were reviewed for monsoonal Asia, from which a difference in drought variability was observed between the northern and southern parts. Therefore, we compared the drought variations of the four sub-regions of western and eastern parts of central High Asia, as well as northern and southern portions of monsoonal Asia. ENSO activity and sea surface temperature of western Pacific and northern Indian Oceans, coupled with Asian monsoon, play an important role in modulating drought variability of much area of the East Asia. An improved denser multi-index tree-ring network of longer length for East Asia is necessary for the establishment of more reliable large-scale drought reconstruction.     

General climatic controls and topoclimatic variations in Central and High Asia

Basic features of current spatial and seasonal climate variations in Central and High Asia are presented. Large-scale circulation modes were inferred from NCAR/CDAS General Circulation Model (GCM) data and interpreted with particular emphasis on the Asian Monsoon circulation. Using spatial high-resolution estimates of radiation, temperature and precipitation covering Central and High Asia in a regular grid network with a grid-cell spacing of 1 km², topoclimatic variations are investigated and discussed with respect to their major barometric and topographic controls. In general, weather patterns of Central and High Asia are determined by tropical monsoon as well as extratropical circulation modes. Associated synoptic conditions and processes, in particular the alternation of tropical and polar air masses, lead to distinct large-scale variations valid for all climatic parameters in all seasons. The regional analysis and discussion of climatic gradients and environmental lapse rates stress the significant role of Asia's marked orography and its influence on advective processes, flow currents and topoclimatic settings. Preliminary estimations of the annual water balance, however, are still afflicted with major uncertainties owing to methodical limits in the spatial estimation of precipitation rates and widely lacking evapotranspiration records, particularly in the Tibetan Plateau and adjacent high mountain systems. Given the importance of the mountainous water resources for the affected economies, further regional investigations on the water cycle and its components are vital future tasks for climate research.     

吉尔吉斯斯坦水资源及其开发利用

吉尔吉斯斯坦共和国地处中亚中心,山地众多,山脉纵横,冰川广泛发育,水资源十分丰富,是中亚五国的"水塔",控制着中亚五国的水资源命脉.吉尔吉斯斯坦经济社会发展潜力巨大且发展意愿十分强烈,研究其水资源及开发利用对找寻妥善的中亚水资源问题解决之道具有十分积极的意义.分析介绍了吉尔吉斯斯坦自然地理以及与水资源形成有关的气候、地形地貌和冰川融雪概况,评价了吉尔吉斯斯坦水资源总量.然后在阐述吉尔吉斯斯坦独立以来至今的社会经济发展概况的基础上,分析介绍了其主要水资源开发工程与水力发电、用水量变化,并对吉尔吉斯斯坦水资源开发利用中存在的主要问题进行了深入剖析.     

Global land water storage change from GRACE over 2002–2009; Inference on sea level

Global change in land water storage and its effect on sea level is estimated over a 7-year time span (August 2002 to July 2009) using space gravimetry data from GRACE. The 33 World largest river basins are considered. We focus on the year-to-year variability and construct a total land water storage time series that we further express in equivalent sea level time series. The short-term trend in total water storage adjusted over this 7-year time span is positive and amounts to 80.6 ± 15.7 km³/yr (net water storage excess). Most of the positive contribution arises from the Amazon and Siberian basins (Lena and Yenisei), followed by the Zambezi, Orinoco and Ob basins. The largest negative contributions (water deficit) come from the Mississippi, Ganges, Brahmaputra, Aral, Euphrates, Indus and Parana. Expressed in terms of equivalent sea level, total water volume change over 2002–2009 leads to a small negative contribution to sea level of –0.22 ± 0.05 mm/yr. The time series for each basin clearly show that year-to-year variability dominates so that the value estimated in this study cannot be considered as representative of a long-term trend. We also compare the interannual variability of total land water storage (removing the mean trend over the studied time span) with interannual variability in sea level (corrected for thermal expansion). A correlation of ∼0.6 is found. Phasing, in particular, is correct. Thus, at least part of the interannual variability of the global mean sea level can be attributed to land water storage fluctuations.