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2002年3月成功发射的美德合作重力卫星计划GRACE(GravityRecoveryAndClimateExperiment)已经开始提供阶次数达到120、时间分辨率为约1个月的地球重力场模型时变序列.GRACE的星座由两颗相距约220km,高度保持300~500km,而倾角保持约90°的近极轨卫星组成.由于采用星载GPS和非保守力加速度计等高精度定轨技术以及高精度的星-星跟踪数据反演地球重力场,在几百公里和更大空间尺度上,GRACE重力场的精度大大超过此前的卫星重力观测.根据GRACE时变重力场反演的地球系统质量重新分布对固体地球物理、海洋物理、气候学以及大地测量等应用有重要的意义.在长期时间尺度上,GRACE的结果可用于研究北极冰的变化,并进而研究极冰融化对全球气候变化,特别是对海平面长期变化的影响.在季节性时间尺度上,利用GRACE重力场的精度足以揭示平均小于1cm的地表水变化或小于1mbar的海底压强变化.除了巨大的社会和经济效益外,这些变化对了解地球系统的物质循环(主要是水循环)和能量循环有非常重要的意义.利用2002年4月至2003年12月之间共15个月的GRACE时变重力场揭示了全球水储量的明显季节性变化,并重点分析了中国长江流域水储量的变化.结果表明长江流域水储量周年变化幅度可达到3.4cm等效水高,其最大值出现在春季和初秋.根据GRACE时变重力场反演的水储量变化与两个目前最好的全球水文模型的符合相当好,其差别小于1cm等效水高.研究表明现代空间重力测量技术在监测一些大流域的水储量变化(如长江流域)、全球水循环和气候变化上有巨大的应用潜力.
The GRACE (Gravity Recovery Animate Experiment), successfully launched in March 2002, has begun to provide time-varying sequences of the Earth’s gravitational field model with orders up to 120 and a temporal resolution of about 1 month.The GRACE constellation consists of two geophones spaced approximately 220 km , A highly polar orbiting satellite with an altitude of 300-500 km and a dip angle of about 90. Because of the use of high-precision orbit determination techniques such as on-board GPS and non-conservative accelerometers and high-precision star-star tracking data to retrieve Earth’s gravity Field, the accuracy of the GRACE gravitational field greatly exceeds that of previous satellite gravimetric observations over hundreds of kilometers and beyond. Based on the mass redistribution of the Earth’s system retrieved from the GRACE time-varying gravitational field, the accuracy of the GRACE gravitational field is strongly influenced by solid geophysics, marine physics, climatology And geodetic applications, etc. On a long-term time scale, the results of GRACE can be used to study changes in Arctic ice and to study the effects of polar ice melting on global climate change, especially on long-term changes in sea level.In the season On the time scale, the accuracy of using the GRACE gravitational field is sufficient to reveal changes in surface water less than 1 cm in average or at sub-1 mbar seafloor pressures In addition to tremendous social and economic benefits, these changes are of great importance for understanding the material cycle (mainly the water cycle) and the energy cycle of the Earth system. Using a total of 15 months between April 2002 and December 2003 The GRACE time-varying gravitational field reveals obvious seasonal changes of global water reserves, and analyzes the changes of water reserves in the Yangtze River basin in China.The results show that the annual variation of water storage in the Yangtze River reaches 3.4cm, and its maximum value Appeared in the spring and early autumn.According to GRACE time-varying gravimetry inversion of water reserves, the change is in good agreement with the two best global hydrological models at present, and the difference is less than 1 cm equivalent water.Research shows that modern spatial gravimetry Monitoring of changes in water reserves in some large basins (such as the Yangtze River basin) has great potential for application in the global water cycle and climate change.