GRACE和地面重力测量监测到的中国大陆长期重力变化

自2002年以来,GRACE卫星探测计划可提供高精度的时变地球重力场,用以探测地球系统的物质分布.自1998年中国大陆重力监测网建立以来,利用FG5绝对重力仪和LCR-G型相对重力仪每2年对该网进行重复测量获取重力场时变信息.基于此,本文利用GRACE和地面重力测量获得了中国大陆重力场的长期年变率,利用位错理论根据USGS发布的断层模型计算了2008年汶川Ms8.0级地震的同震重力变化并进行了300 km高斯滤波.GRACE卫星重力和地面重力结果均表明华北地区地下水流失严重,在绝对重力基准站上,GRACE卫星重力与绝对重力变化率较为一致,汶川区域的地面重力变化结果可视为大地震前兆信息.     

基于国产卫星数据的矿山遥感监测一体化解决方案——以西藏自治区为例

随着高分辨率国产遥感卫星数据的推广应用,矿山遥感监测必将成为该数据的重要应用领域之一。结合西藏自治区矿山遥感监测工作的特点,以资源一号02C(ZY-1 02C)及高分一号(GF-1)卫星影像为数据源,在ArcGIS环境下,提出并实现了从国产卫星遥感数据管理、增强与校正、信息提取、统计分析以及成果图制作等一体化解决方案。该研究成果有助于推进国产卫星遥感数据在矿山遥感监测领域的应用广度和深度,为大规模开展多期次动态矿山遥感监测工作提供技术支持和应用范例。     

Analysis of water resources in the Mahanadi River Basin,India under projected climate conditions

The paper presents the outcomes of a study conducted to analyse water resources availability and demand in the Mahanadi River Basin in India under climate change conditions. Climate change impact analysis was carried out for the years 2000, 2025, 2050, 2075 and 2100, for the months of September and April (representing wet and dry months), at a sub‐catchment level. A physically based distributed hydrologic model (DHM) was used for estimation of the present water availability. For future scenarios under climate change conditions, precipitation output of Canadian Centre for Climate Modelling and Analysis General Circulation Model (CGCM2) was used as the input data for the DHM. The model results show that the highest increase in peak runoff (38%) in the Mahanadi River outlet will occur during September, for the period 2075–2100 and the maximum decrease in average runoff (32·5%) will be in April, for the period 2050–2075. The outcomes indicate that the Mahanadi River Basin is expected to experience progressively increasing intensities of flood in September and drought in April over the considered years. The sectors of domestic, irrigation and industry were considered for water demand estimation. The outcomes of the analysis on present water use indicated a high water abstraction by the irrigation sector. Future water demand shows an increasing trend until 2050, beyond which the demand will decrease owing to the assumed regulation of population explosion. From the simulated future water availability and projected water demand, water stress was computed. Among the six sub‐catchments, the sub‐catchment six shows the peak water demand. This study hence emphasizes on the need for re‐defining water management policies, by incorporating hydrological response of the basin to the long‐term climate change, which will help in developing appropriate flood and drought mitigation measures at the basin level. Copyright © 2008 John Wiley & Sons, Ltd.     

On the coupling of lunisolar resonances for Earth satellite orbits

The resonance C1 occurs when the longitude of the perigee measured from the equinox becomes a slow angle in the doubly averaged equations of motion. This resonance is one of the critical inclination family with I 46°. For prograde Earth satellite orbits, up to five critical points can be identified. Only simple pitchfork bifurcations occur for the single resonance C1. A two degrees of freedom system is studied to check how a coupling of two lunisolar resonances affects the results furnished by the analysis of an isolated resonance case. In the system with two critical angles (g+h and h,+2 , seven types of critical points have been identified. The critical points arise and change their stability through 11 bifurcations. If the initial conditions are selected close to the critical points, the system becomes chaotic as shown in Poincaré maps.     

Effect of climate change on drinking water supply in Santiago de Chile

Climate change is likely to increase the occurrence of floods and flashfloods that affect Santiago de Chile's drinking water supply system throughout the 21st century. A relationship between flashfloods in the Maipo River--Santiago's main raw water source, drainage area in the Maipo Alto Sub Basin and precipitation 48 hours previous to the event was found. Despite having legal guidelines to guarantee continuity and stability in water supply, Chilean law does not specify the maximum admissible magnitude of an event. A 12% drop of average monthly flow at Maipo en El Manzano Station was estimated for the 2035-2065 period due to climate change, meaning water suppliers would not be able to meet 90% monthly water supply security, required by Chilean law. Water suppliers would need to increase their current allotted quota of the Maipo River, from 24.5% to a percentage between 26% and 30% to comply. If the 0 °C isotherm keeps increasing its elevation through the 21st century, more intense floods could occur because of additional drainage area granted by the elevation of the snow line, even if precipitation does not suffer a significant change. In order to withstand a five day turbidity event, 2 m 3 /s of groundwater, or any non river source, should be temporarily incorporated to the emergency drinking water production.     

Albedo perturbation models: General formalism and applications to LAGEOS

The force due to radiation pressure on a satellite of arbitrary shape is written in a general form within a formalism similar to that used in the theory of radiative transfer in atmospheres. Then the corresponding integrals are evaluated for the simple case of a spherically symmetric satellite, and applied to model the perturbation due to the Earth-reflected radiation flux on LAGEOS. For this purpose, the optical behaviour of the Earth's surface and atmosphere is described as a combination of Lambertian diffusion (continents), partial specular reflection consistent with Fresnel law (oceans) and anisotropic diffusion according to Chandrasekhar's radiative transfer theory (clouds). The in-plane Gauss componentsT andS vs. mean anomaly are computed for a simple orbital geometry and for different models of the Earth's optical properties. A sensitive dependence is found on the assumed cloud distribution, with significant perturbations possibly arising from oceanic specular reflection when the satellite is close to the Earth's shadow boundaries.On leave from Astronomical Institute, Charles University, védská 8, 15000 Prague 5, Czechoslovakia