Global Mass Change Analysis In Recent Ten Years By GRACE RL05 Data

The change of earth gravity field reflect the mass change on the Earth, the earth’s mass distribution is not stable. The densely populated and economic development regions lack water seriously. In some areas, excessive groundwater extractionsc have led to rapid decline in water reserves. Influenced by the global climate change, the glaciers have melted in the polar region. It provides a method for measuring large-scal mass changes since GRACE launch.In this thesis, the data of GRACE RL05 are used to estimate the earth mass variations from January 2003 to December 2012. Some specific areas where mass change significantly are analyzed in detail. The specific content and results of this thesis are summarized as follows:(1) The development of satellite gravity and results of previous research are briefly described. The theories and methods to calculate mass variations of the earth from GRACE temporal gravity field model data are analyzed in detail. This study especially describes some methods on the post-processing removal of correlated errors in GRACE data and analyzes the effect to eliminate strips. The border coefficients can not be directly fitted according to the characteristics of traditional de-correlated filtering algorithms. Here, an improved de-correlated filtering algorithm is presented. The algorithm sets the highest order coefficient to be fitted up to 55 and the border coefficient can be directly fitted without used as center of the sliding window. The algorithm is proposed with significant decrease in stripes.(2) The second part of this thesis analyzes the global water reserves variations on seasonal and inter-annual trends. Somes local areas where water reserves variations significantly are chosen to discusse, such as Chinese Mainland, the India peninsula and the amazon basin. The result show that the change of land water storage is increasing in the three gorges region and Altun Mountains region in the Xinjiang Uygur Autonomous Region since 2003 to 2012, just the opposite in north China. Reduced rate of the groundwater in north China is 4.1mm/yr. During the study period, the change of water storage is mainly from 2004 to 2008 in north China. The groundwater reduction is the main cause of gravity changes. The equivalent water height has change three times in the Three Gorges Reservoir, which are 52mm、18mm and 7mm, while respectively, the main cause is the Three Gorges Dam reservoir. The results show that the gravity changes caused by surface reservoirs can be observed by GRACE. The surface water firstly increases, then decrease and finally tends to be stable in the Xinjiang Uygur Autonomous Region. The surface water appears a sudden increase in 2005. During the studying period, the rate of terrestrial water and groundwater variations is 10.6mm/yr and 11.6mm/yr, respectively.The groundwater change in a broader region covering Northwest India, it decline occurred mainly before 2010. The rate of change is-16.5mm/yr before 2010, and then tend to be stable. During the recent ten years, the groundwater of Northwest India reduces at the rate of-15.3mm/yr. Strong annual and semi-annual signal can be found in India peninsula and amazon basin. The maximum amplitude and phase of annual is 176mm and 126d, respectively. The maximum amplitude of semi-annual is 79mm. The water reserves are affected by seasonal change is the main due to precipitation.(3) In the last part of this thesis, the ice melting rate in the Greenland and Antarctic ice sheet and the sea-level changes obtained from the ice melting are studied. The impact of the glacial isostatic adjustment (GIA) correction to ice mass variation is compared with different GIA models. The results show that the melting of Antarctic ice mass mainly results from the melting of West Antarctic while accumulating in the East Antarctic. The melting of the Antarctic ice mass is accelerating. During the studying period, the melting rate and acceleration of the Antarctic ice mass are -75.5±40.3 Gt/yr and -21±4.0 Gt/yr, its corresponding contributies 0.20±0.11 mm/yr、0.06±0.01 mm/yr2 to the global sea-level rise. The melting of Greenland ice mass mainly results from the melting of South and northwest ice sheet. Greenland ice sheet melting faster since 2010. The melting rate and acceleration of the Greenland ice mass are -162.3±21.8 Gt/yr、-17.7±4.5 Gt/yr2 between 2003 and 2012, its corresponding contributies 0.20±0.11 mm/yr、0.06±0.01 mm/yr2 to the global sea-level rise 0.45±0.06 mm/yr、0.05±0.01 mm/yr2,GIA model is an important factor to the melting ice mass, the GIA model error is also the main error source for the mass change of ice.Strong annual signal also can be found in Antarctic and Greenland. The maximum amplitude and phase of annual is 8.1mm and 300d in Antarctic. The annual variation influence mainly exists in the south Greenland, the amplitude of mass change reachs the maximum every May. The phase is consistent with temperature change.